Discussion:
Re: [Icom] Opinions re: HF Verticals?
(too old to reply)
Doug Person
2002-10-11 14:01:00 UTC
Permalink
I can't agree with this. I have had a GAP Titan up for 6 years. It easily
outperformed the R5 it replaced and is generally always as good or better
than the ground-mounted homebrew verticals I have had for 20 and 40 meters
(minimum of 16 radials each).
But, for my money, the best darn commercial antenna I've ever owned is a
W9INN 5 band dipole. It's only 60 feet long and covers 80, 40, 20, 15 and
10. On 80 meters it only covers 25KHz - but that's fine. I only care about
the DX window. On 40 it covers about 200KHz. On 20 - 10 it's pretty much
like any other dipole. And, yes, it eats the GAP's lunch any day of the
week.

Doug -- W4DXV

----- Original Message -----
From: "John Geiger" <***@yahoo.com>
To: <***@mailman.qth.net>
Sent: Thursday, October 10, 2002 10:40 PM
Subject: Re: [Icom] Opinions re: HF Verticals?
Don't waste your money on a GAP vertical. They are
greatly overpriced, ugly as sin, and don't perform
better than any other vertical. Get a Hustler, or
Cushcraft, and go to it. Used to have a HyGain 40-10
meter vertical, and it worked wonders ground mounted
with no radials. Also had a Cushcraft R4 for awhile.
It covered 20, 15, 12, and 10 meters, with no radials,
but the SWR changed whenever it rained. The hustlers
are rated as good as anything else to day, and less
than half the cost. Do hear good things about the
Butternut HF2V if you want it for 80/40 only
73s John NE0P
Nonsense . . .
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county
EM13qe
K2 #489 Icom IC-765 #2349 Icom IC-756 PRO
#2121
Well, no vertical will work as well as your wire
antenna, but I may put up
another vert. Probably another Hustler. The
butternut is junk. I had one,
and gave it away!
----
Your Moderator: Dick Flanagan W6OLD,
Icom FAQ: http://www.qsl.net/icom/
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Stuart Rohre
2002-10-14 20:16:05 UTC
Permalink
I have had all type of antennas, even some most hams only dream about.
(Rhombic, Vee beam 10 waves on 10m, 400 foot long wire, dipoles, quarter
wave vertical, trap verticals like Cushcraft, Butternut, etc.)

Now I have the Gap Titan for some 7 or 8 years. Best performing vertical
over the R7, R5, Butternut, and some horizontal antennas. It is equal to my
best dipole, and excels on DX. It has NO traps, only aluminum stubs so the
parallel lines act as traps but without coil loss, or lumped capacitance.
The only compromise stub is the 80m capacitor loaded one. It is an adequate
performer on that band.

If you could get the aluminum and insulators, sure you could build your own
Titan, but your labor must be worth something. Much easier to get the kit.
Aluminum tubing in many sizes is harder to come by these days.

No one antenna is always the best, so I have a combination. One of the best
all around performers for me have been very large horizontal loops, put up
no more than 20 feet high! With one 849 feet around, we worked Indonesia at
QRP phone last Field Day. IDEZ antennas I developed are also excellent
performers, but require a transmatch as does the large loops for all band
use.
(Inverted vee Double Extended Zepps). We use open wire feeders for those
big wires.
72, Stuart K5KVH
Mike McCoy
2002-10-15 01:11:01 UTC
Permalink
Well I broke down and ordered a Force 12 Sigma GT5 (no-trap/no radial
vertical dipole) today.

Since I have no horizontal space for a dipole I've been investigating
verticals for a while. The thing that has put me off (aside from the need to
plant radials) is that for virtually every vertical manufacturer it seems
1/2 of owners love em and the other 1/2 can't get rid of them fast enough.

Except for Force 12... I haven't heard one person say anything (really)
negative about Force 12 antennas. And apparently they can't keep the Sigma 5
in stock (backordered 3-4 weeks).

And here's a very interesting new antenna from Force 12 just now available,
a 16' 40-10 vertical dipole:

http://force12inc.com/sigma40XKinfo-001.htm

Not bad for $249...

Mike - AD5IU

----- Original Message -----
From: "Stuart Rohre" <***@arlut.utexas.edu>
To: "Doug Person" <***@attglobal.net>; "elecraft"
<***@mailman.qth.net>
Sent: Monday, October 14, 2002 2:04 PM
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?
Post by Stuart Rohre
I have had all type of antennas, even some most hams only dream about.
(Rhombic, Vee beam 10 waves on 10m, 400 foot long wire, dipoles, quarter
wave vertical, trap verticals like Cushcraft, Butternut, etc.)
Now I have the Gap Titan for some 7 or 8 years. Best performing vertical
over the R7, R5, Butternut, and some horizontal antennas. It is equal to my
best dipole, and excels on DX. It has NO traps, only aluminum stubs so the
parallel lines act as traps but without coil loss, or lumped capacitance.
The only compromise stub is the 80m capacitor loaded one. It is an adequate
performer on that band.
If you could get the aluminum and insulators, sure you could build your own
Titan, but your labor must be worth something. Much easier to get the kit.
Aluminum tubing in many sizes is harder to come by these days.
No one antenna is always the best, so I have a combination. One of the best
all around performers for me have been very large horizontal loops, put up
no more than 20 feet high! With one 849 feet around, we worked Indonesia at
QRP phone last Field Day. IDEZ antennas I developed are also excellent
performers, but require a transmatch as does the large loops for all band
use.
(Inverted vee Double Extended Zepps). We use open wire feeders for those
big wires.
72, Stuart K5KVH
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Vic Rosenthal
2002-10-15 04:04:01 UTC
Permalink
Post by Mike McCoy
And here's a very interesting new antenna from Force 12 just now available,
http://force12inc.com/sigma40XKinfo-001.htm
Not bad for $249...
It's a very nice antenna, but keep in mind that it can be set up for any ONE
band from 5-30 MHz -- it is NOT a multiband antenna.

Vic K2VCO
Mike McCoy
2002-10-15 13:41:00 UTC
Permalink
Apparently this is their first iteration of this design. The multiband
switchable version is supposed to be available this Winter.
Post by Vic Rosenthal
It's a very nice antenna, but keep in mind that it can be set up for any ONE
band from 5-30 MHz -- it is NOT a multiband antenna.
Mike - AD5IU
Hank Kohl
2002-10-15 04:33:13 UTC
Permalink
Post by Vic Rosenthal
Post by Mike McCoy
And here's a very interesting new antenna from Force 12 just now available,
http://force12inc.com/sigma40XKinfo-001.htm
Not bad for $249...
It's a very nice antenna, but keep in mind that it can be set up for any ONE
band from 5-30 MHz -- it is NOT a multiband antenna.
True it's not automatic or remotely switched, but it is multi-band with
manual, physical switching.

The Sigma5 is 20-17-15-12-10M with relay control to change bands.
A friend of mine used a couple of these on his last trip to the Pacific and
said they performed great.
Not bad for $349 and very portable.

73 Hank K8DD
Stuart Rohre
2002-10-15 19:59:02 UTC
Permalink
Tom Schiller at Force 12 is a good antenna guru. He has done his homework,
and the vertical half wave dipole is an excellent vertical antenna, with the
usual advantage of low angle lobes for good DX work.

No vertical will do some things a horizontal will, nor will a horizontal do
all things a vertical can do. Sometimes one or the other will do what is
normally associated with the other.

Close in working is not the main forte of verticals, but can be done when
conditions are right with good signal reports. It can hear just fine, it is
the strength of the close in transmit that is down since most of the energy
is going out in the low angle lobes to DX locations.

That said, the loaded shortened half wave vertical, with loading coils to
match it can also give a fine accounting. As the books will tell you, and
W4RNL has extensively modeled, and written; a dipole can be shortened to 60
per cent of normal length and still be highly efficient. Thus, Force 12 has
taken basic physics and made very effective antennas for 40 to 10 on the
vertical center feed principle. Since there are two halves to the antenna
no radial system is needed. Any ground enhancement would have to come in
the far field, usually at 2 to 5 wavelengths away, well beyond the usual
ham's control.

The people who do not like verticals either do not understand they are
superior for low angle DX, and want them to do close in work all the time,
or they do not have an adequate ground system or radial system if using
"half an antenna"-- the quarter wave vertical and its loaded equivalents.
There are some loaded quarter wave type antennas, that are much less than 60
per cent of full length, where efficiency remains high on the dipole types.

The shortened verticals will work sometimes much better than an excessively
low dipole. They have many advantages some are: little real estate
required above ground, and easily hidden behind the house in the back yard.
For antenna challenged hams they may be a viable solution.

Force 12 is one of the few antenna companies whose designers regularly
partake of DX -peditions and test out their designs in real world
operations.
Look at their web page for excellent troubleshooting information on any
antenna as well.

Although I do not own one at present, we have bought them for research work
and find they do things as advertised. Many personal visits with Tom have
also shown me he knows antennas!
72, Stuart K5KVH
Vic Rosenthal
2002-10-15 21:15:01 UTC
Permalink
Post by Stuart Rohre
The people who do not like verticals either do not understand they are
superior for low angle DX, and want them to do close in work all the time,
Over poor or just OK ground, even a vertical with a good radial system will
compare poorly for DX to a horizontal dipole at more than a half-wavelength
above ground for DX. The theoretical pattern is subject to a big suck-in at low
angles caused by poor ground in the Fresnel zone a few wl from the antenna. So
above 7 MHz (wl/2 = 70 ft) most of us can build a horizontal antenna that is
more effective than an excellent vertical (like the Force-12 verticals).
Post by Stuart Rohre
or they do not have an adequate ground system or radial system if using
"half an antenna"-- the quarter wave vertical and its loaded equivalents.
Even a vertical dipole or a monopole with 120 radials behaves as above.

By the way, Stuart, I don't know where you are located but some areas in Texas
have very high ground conductivity and these places are, so to speak, fertile
ground for verticals!

73
Vic K2VCO
k***@ENTERZONE.NET
2002-10-15 06:48:01 UTC
Permalink
Post by Hank Kohl
The Sigma5 is 20-17-15-12-10M with relay control to change bands.
A friend of mine used a couple of these on his last trip to the Pacific and
said they performed great.
Not bad for $349 and very portable.
73 Hank K8DD
I just looked at the site and it looks "interesting" except for the fact
that they claim 2:1VSWR over an adjustable 320Khz segment of 20m. Am I
just anal retentive of are there others out there that consider any
supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
antenna?

If I want 2:1, I can switch in most any of my antennas, on nearly any band
and get very close to 2:1 with no tuner. When it comes to resonant
antennas, I want to see 1.2:1 or better and will spend quite a bit of time
looking for as close to 1.0:1 when putting up an antenna.

My 75m antenna is 1.01:1 at 3.875 (one of my ragchew favs) and the 160m
loop is 1.03:1 at 1.898.

I consider an antenna that requires a tuner to operate at its design
frequnency with less than 1.5:1 to be a compromise at best. When the fit
hits the shan and I need to get on the air in an emergency, I don't want
to be twiddling with a tuner and I also don't want to risk blowing up the
amplifier.

Maybe I just think differently. To me, the transmatch, in the grand
scheme of things, is another potential point of failure when you're
DEPENDING on your communications equipment for emergency comm.

For ragchew, no problem. Twist some knobs, press the tune button, do
whatever it takes.

73 de John - KC4KGU
K2/100 #2490
sjolin
2002-10-15 07:48:00 UTC
Permalink
----- Original Message -----
From: <***@ENTERZONE.NET>
To: "Hank Kohl" <***@arrl.net>
Cc: "Elecraft" <***@mailman.qth.net>
Sent: Tuesday, October 15, 2002 12:39 AM
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?
Post by k***@ENTERZONE.NET
that they claim 2:1VSWR over an adjustable 320Khz segment of 20m. Am I
just anal retentive of are there others out there that consider any
supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
antenna?
What they are saying is that at no point over the 320 khz range does the swr
exceed 2:1. It maybe 1:1 at 14.160 and 2:1 at 14.000 and 14.320. Most
commercial antennas for 20 meters will have similar ratings and they are
resonant.
Post by k***@ENTERZONE.NET
I consider an antenna that requires a tuner to operate at its design
frequnency with less than 1.5:1 to be a compromise at best.
Most rigs will accept swr of 2:1 without reducing the power appreciably if
at all. And even if you are using coax, you are probably not going to notice
any loss in signal strength betwen 1:1 and 2:1. With this kind of swr you
are not likely to need an antenna tuner unless you are a purist, fiddler, or
have a very finicky rig. Also if you only operate cw near the qrp frequency
than the simple solution to this non problem is to adjust reasonance to
14.08 or so and then the entire cw portion of the band will be at what you
characterize as an acceptable swr. This obviously wont work if you also want
to operate SSB on 14.313 (but why would anyone).

BTW, an antenna can be resonant and have an swr of 1.5:1 or 2:1. This has
to do with impedance matching, not reasonant frequency. For example, the
directions for my Butternut HF-2V vertical point out that the swr at
resonance may be 1.5:1 or higher because the radiation resistance of the
antenna is very low relative to the impedance of the coax cable. The
vertical uses a length of 72 ohm coax and in some configurations a small
coil across the coax connection at the antenna to better match the antenna
to the feedline.

73 de Dave, N0IT
John Fraizer - KC4KGU
2002-10-15 08:06:00 UTC
Permalink
Post by sjolin
Post by k***@ENTERZONE.NET
that they claim 2:1VSWR over an adjustable 320Khz segment of 20m. Am
I just anal retentive of are there others out there that consider any
supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
antenna?
What they are saying is that at no point over the 320 khz range does the
swr exceed 2:1. It maybe 1:1 at 14.160 and 2:1 at 14.000 and 14.320.
Most commercial antennas for 20 meters will have similar ratings and
they are resonant.
OK. Wrong word. Non-matched I suppose is what I should have used.
Post by sjolin
Post by k***@ENTERZONE.NET
I consider an antenna that requires a tuner to operate at its design
frequnency with less than 1.5:1 to be a compromise at best.
Most rigs will accept swr of 2:1 without reducing the power appreciably
if at all. And even if you are using coax, you are probably not going to
notice any loss in signal strength betwen 1:1 and 2:1. With this kind of
swr you are not likely to need an antenna tuner unless you are a purist,
fiddler, or have a very finicky rig.
My K2 gets a bit miffed if I present it with 2:1 and I can most definately
hear a difference between 1:1 and 2:2 when I'm tuning loop for use on
higher bands with the transmatch. It's not as bad as being out to 4:1 or
so but, you can hear a difference.
Post by sjolin
band will be at what you characterize as an acceptable swr. This
obviously wont work if you also want to operate SSB on 14.313 (but why
would anyone).
When I put up antennas, they're for QRO(and many more O's) operation.
While the amp will probably survive 2:1, I wouldn't personally operate it
that way unless it was under some sort of emergency and there was no other
choice.

I know - the answer is a transmatch. I'm talking about the "oh crap"
situation here. You have to communicate using HF, conditions are bad and
you have to run the AMP and your transmatch is DOA.
Post by sjolin
BTW, an antenna can be resonant and have an swr of 1.5:1 or 2:1. This
has to do with impedance matching, not reasonant frequency. For example,
I follow. I used the wrong term previously. I have a transmatch but,
whenever possible, it's in bypass mode. Most of my antennas are pretty
broadbanded at less than 1.5:1.
--
73 de John - KC4KGU
K2/100 #2490
http://www.kc4kgu.com
George, W5YR
2002-10-15 07:52:00 UTC
Permalink
John, I really don't know if you are anal retentive or not, but an antenna
can be resonant and still present a 10:1 SWR to the feedline.

The absolute magnitude of VSWR is not an indicator of resonance.

Resonance is solely, only and always the condition of a tuned circuit in
which the impedance at the port of interest is purely resistive or real.
The real component may NOT be the same as the Zo of a transmission line,
hence the SWR can be other than 1:1.

Resonance has nothing to do with SWR. SWR is determined solely by the ratio
of the driving point impedance of the antenna to the Zo of the transmission
line, or vice versa.

It is your choice to place so much emphasis on SWR but the facts are that
it is relatively unimportant to the actual radiation performance of an
antenna. An antenna fed with a line having any SWR will radiate all the
power it receives. If the line is low-loss, it can easily be the case that
more power is delivered to the antenna over a line with a 20:1 SWR than a
line with a 2:1 SWR. It is all a question of relative line loss, frequency,
line length, etc.

But the resonance or lack thereof of the antenna has very little to do with
it. Every antenna that I use, except for my Butternut HF9V vertical, is
non-resonant in any amateur band. They all work great on 80 through 10
meters, and most of my operating is QRP CW where efficiency counts.

With all respect, John, a review of the Antenna Book on the topics of
antenna resonance might be worth your time. Walt Maxwell's "Reflections II"
will give you an entirely new outlook on this subject. Resonance is
convenient for matching purposes, but that is about all it buys for you.

BTW, how are you measuring those 1.01:1 and 1.03:1 SWR values? And what do
you figure that they provide for you that 1.5:1 would not? Just curious . .
. <:}

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489 Icom IC-765 #2349 Icom IC-756 PRO #2121
Post by k***@ENTERZONE.NET
Post by Hank Kohl
The Sigma5 is 20-17-15-12-10M with relay control to change bands.
A friend of mine used a couple of these on his last trip to the Pacific and
said they performed great.
Not bad for $349 and very portable.
73 Hank K8DD
I just looked at the site and it looks "interesting" except for the fact
that they claim 2:1VSWR over an adjustable 320Khz segment of 20m. Am I
just anal retentive of are there others out there that consider any
supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
antenna?
If I want 2:1, I can switch in most any of my antennas, on nearly any band
and get very close to 2:1 with no tuner. When it comes to resonant
antennas, I want to see 1.2:1 or better and will spend quite a bit of time
looking for as close to 1.0:1 when putting up an antenna.
My 75m antenna is 1.01:1 at 3.875 (one of my ragchew favs) and the 160m
loop is 1.03:1 at 1.898.
I consider an antenna that requires a tuner to operate at its design
frequnency with less than 1.5:1 to be a compromise at best. When the fit
hits the shan and I need to get on the air in an emergency, I don't want
to be twiddling with a tuner and I also don't want to risk blowing up the
amplifier.
Maybe I just think differently. To me, the transmatch, in the grand
scheme of things, is another potential point of failure when you're
DEPENDING on your communications equipment for emergency comm.
For ragchew, no problem. Twist some knobs, press the tune button, do
whatever it takes.
John Fraizer - KC4KGU
2002-10-15 08:18:00 UTC
Permalink
Post by George, W5YR
The absolute magnitude of VSWR is not an indicator of resonance.
Granted. When you're operating resonant antennas and the antenna is
supposed to presenting a 50Ohm load to your rig (via whatever _static_
means, no adjustable transmatch here) VSWR will indicate that you're
operating outside of resonance. Since I operate all resonant antennas, I
think in terms of ANY VSWR when operating at the design frequenct == BAD
Post by George, W5YR
With all respect, John, a review of the Antenna Book on the topics of
antenna resonance might be worth your time. Walt Maxwell's "Reflections
II" will give you an entirely new outlook on this subject. Resonance is
convenient for matching purposes, but that is about all it buys for you.
I beg to differ. It will also buy you different radiation patterns.
Post by George, W5YR
BTW, how are you measuring those 1.01:1 and 1.03:1 SWR values? And what
do you figure that they provide for you that 1.5:1 would not? Just
curious . . . <:}
RF Applications VFD http://www.rfapps.com/vfd.htm

They provide me the piece of mind that I'm seeing 1.03:1 and not 1.5:1 or
2:1 or whatever else.
--
73 de John - KC4KGU
K2/100 #2490
http://www.kc4kgu.com
sjolin
2002-10-15 08:30:00 UTC
Permalink
----- Original Message -----
From: "John Fraizer - KC4KGU" <***@enterzone.net>
To: <***@att.net>
Cc: <***@mailman.qth.net>
Sent: Tuesday, October 15, 2002 2:09 AM
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?
Post by John Fraizer - KC4KGU
Granted. When you're operating resonant antennas and the antenna is
supposed to presenting a 50Ohm load to your rig (via whatever _static_
means, no adjustable transmatch here) VSWR will indicate that you're
operating outside of resonance. Since I operate all resonant antennas, I
think in terms of ANY VSWR when operating at the design frequenct == BAD
John, plot the vswr of your antenna at various points across the band. The
point at which swr is lowest is likely where the antenna is resonant but as
George said the swr at that point can be well in excess at the 2:1 level
even though its at resonance. Also remember you are reading swr at the rig
and swr should be measured at the antenna. Changing the length of coax used
to feed an antenna will change the swr at the rig. I've seen cases where the
swr will change just by adding an extra couple feet of cable in the shack.

73 de Dave, N0IT
W2AGN
2002-10-15 19:21:00 UTC
Permalink
Post by Larry East
Post by sjolin
Changing the length of coax used
to feed an antenna will change the swr at the rig. I've seen cases where the
swr will change just by adding an extra couple feet of cable in the shack.
That is incorrect -- if your "SWR Meter" is indeed measuring SWR. The
complex impedance seen by the rig (or tuner) will change depending on the
length of coax, but not the "true" SWR. For an insight into this, read
Chapters 7, 8 and 9 in "Reflections II" by M. Walter Maxwell, W2DU. A most
illuminating book that should be read by every "technically oriented" ham...
73,
Larry W1HUE/7
PS - PLEASE lets DON'T start a big thread on SWR, complex impedances, etc.!
At least take it to QRP-L. Call it the "Deja Vu-Conjugate Matches"
thread.

--
_ _ _ _ _
/ \ / \ / \ / \ / \ John L. Sielke
( W )( 2 )( A )( G )( N ) http://www.w2agn.net
\_/ \_/ \_/ \_/ \_/ QRPARCI, NJQRP, ARQrp,GQRP,RSGB
Ex- K3HLU, TF2WKT, W7JEF, W4MPC, N4JS
George, W5YR
2002-10-15 16:44:00 UTC
Permalink
John, this is largely off-topic for this list so this will be my last
posting on this . . .
Post by John Fraizer - KC4KGU
Post by George, W5YR
The absolute magnitude of VSWR is not an indicator of resonance.
Granted. When you're operating resonant antennas and the antenna is
supposed to presenting a 50Ohm load to your rig (via whatever _static_
means, no adjustable transmatch here) VSWR will indicate that you're
operating outside of resonance. Since I operate all resonant antennas, I
think in terms of ANY VSWR when operating at the design frequenct == BAD
Again, the basic question arises as to the supposed vs the actual merits of
operating "resonant" antennas. But, that appears to be your preference . .
.

That assumes that you have taken care of the non-Zo-match condition by some
form of impedance matching at the antenna. Almost invariably, an antenna
driving-point impedance will NOT exactly match the line Zo, certainly to
the 1.01:1 level, so something has to be adjusted somewhere to reduce the
line SWR to whatever you or the transmitter considers acceptable. Some
folks like to do it at the antenna, some folks fiddle with line lengths,
others like myself prefer the convenience of doing it on the operating desk
with a box with knobs called a tuner. Either way, the same thing gets done
with the same result: the transmitter sees a 50-ohm resistive load.

So, you have a certain VSWR - as low as possible for your taste - at some
selected frequency (not necessarily a resonant frequency, by the way) - and
any departure from that reference value you regard as a change in the
antenna system and you equate that change to BAD. It clearly indicates a
change of some sort. You are certainly within your rights to do that, but I
and several others are merely telling you that there is no engineering
basis for doing so. The change may produce miniscule effects on your
radiated power but these are readily compensated.
Post by John Fraizer - KC4KGU
Post by George, W5YR
With all respect, John, a review of the Antenna Book on the topics of
antenna resonance might be worth your time. Walt Maxwell's "Reflections
II" will give you an entirely new outlook on this subject. Resonance is
convenient for matching purposes, but that is about all it buys for you.
I beg to differ. It will also buy you different radiation patterns.
Perhaps in some extreme cases, such as changing from one band to another,
but consider this: you have your perfect antenna set up for 14.227 MHz; SWR
is 1.007:1 and you are very happy. Your dipole antenna has the usual dipole
pattern in three dimensions. Now you QSY to 14.007 MHz to work some DX.
Your antenna is no longer resonant - assuming it was at 14.227 which is
possible but not necessarily the case (the antenna system was resonant, not
necessarily the actuall radiation "antenna") - so the line SWR changes.

Now tell me what change there is in the pattern, assuming that you provide
the same amount of power to the antenna as you did at 14.227. You can do
this by merely changing the impedance matching of the line input to the
transmitter and if necessary increasing the transmitter power output by an
amount equal to the (usually) negligible added line loss. Why did changing
frequency and having the radiating antenna non-resonant change the antenna
pattern: how and by how much and how does one measure this change?
Post by John Fraizer - KC4KGU
Post by George, W5YR
BTW, how are you measuring those 1.01:1 and 1.03:1 SWR values? And what
do you figure that they provide for you that 1.5:1 would not? Just
curious . . . <:}
RF Applications VFD http://www.rfapps.com/vfd.htm
I note that no accuracy specification is given at the URL for your unit.
Rather they ask you to "compare with the Bird 43 . . ." The Bird is rated
at +/- 5% of full scale. If you will work with that accuracy figure and go
through the equations for computing VSWR from forward and reflected power
measurements - which is what your instrument does wioth its microcomputer -
you will find that there is no way that it could actually compute the
difference between a 1.01 and a 1.03 SWR. The instrument may well display
such readings, but they are an artificial artifact of the processing, not
reflective of the accuracy of the raw power data.
Post by John Fraizer - KC4KGU
They provide me the piece of mind that I'm seeing 1.03:1 and not 1.5:1 or
2:1 or whatever else.
John, I think your statement there pretty well sums it up. You enjoy
operating your station with instrumentation and antenna systems that show
you what you regard as near perfection in transmission line operation - and
recall that VSWR concerns itself with one thing only: how well the line
matches the load - even though the facts of the matter may be significantly
different.

From an engineering viewpoint, the additional loss, change in line input
impedance, stress on the feedline, or any other attribute of "high SWR"
occasioned by changing SWR from 1.01:1 to 1.5:1 can hardly be measured with
any realistic level of accurary. Clearly the practical effects on overall
performance are negligible.

But, what makes you happy and lets you enjoy your station operation is what
counts . . .

Enjoy in good health!

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489 Icom IC-765 #2349 Icom IC-756 PRO #2121
Larry East
2002-10-15 18:34:00 UTC
Permalink
Post by sjolin
Changing the length of coax used
to feed an antenna will change the swr at the rig. I've seen cases where the
swr will change just by adding an extra couple feet of cable in the shack.
That is incorrect -- if your "SWR Meter" is indeed measuring SWR. The
complex impedance seen by the rig (or tuner) will change depending on the
length of coax, but not the "true" SWR. For an insight into this, read
Chapters 7, 8 and 9 in "Reflections II" by M. Walter Maxwell, W2DU. A most
illuminating book that should be read by every "technically oriented" ham...

73,
Larry W1HUE/7

PS - PLEASE lets DON'T start a big thread on SWR, complex impedances, etc.!
Larry East
2002-10-15 22:16:00 UTC
Permalink
True Larry, but I had already said that he had to measure true swr at the
antenna. I was simply pointing out that if he wanted to lower the swr in his
shack to get it down to his vaunted 1:1 so his rig wouldnt reduce output, he
could mess around inside.
Well, I believe that you are perhaps confused - or at least confusing
others - about SWR. If one uses a "reflectometer" to measure forward and
reflected power on a relatively loss-less transmission line, it matters not
where the measurement is done along the transmission line -- one will still
get the correct SWR. It also matters not where one does the matching -- at
the antenna, at the rig or someplace in between.

One only needs to make changes in the transmission line length if the
matching device at the transmitter end (ATU, xmitr tank circuit, whatever)
has a limited impedance matching range; then it might be necessary to
fiddle around with the line length to get the input impedance of the line
within the range that can be matched.

One does not get a "1:1 SWR" at the transmitter output using a matching
device between the transmitter and the antenna, but rather a 1:1 impedance
match. The SWR on the transmission line between the matching device and the
antenna feed-point is not altered.

If you haven't read "Reflections II", you really should. It clears up a lot
of mysteries and misconceptions about transmission lines, SWR and antenna
matching.

73,
Larry, W1HUE/7
Stuart Rohre
2002-10-15 22:10:01 UTC
Permalink
Folks, let me point out, that the photo of the referenced digital readout
SWR meter shows the pickup circuit with clarity. It is the Stockton meter
circuit used by many in QRP Community.

It is a good, but simple, circuit with no magic accuracy capability. Even
with 1 per cent resistors, I seriously doubt it will do 0.01 SWR readouts
with that accuracy. But, SWR is used by finding a MINIMUM what ever the
value.

If you have a dipole antenna, you will not find a 50 ohm 1:1 point if the
antenna is at optimum height, for its feedpoint is actually closer to 72
ohms.

The Bird meter this meter is compared to, carries manufacturers specs of 5
per cent as George pointed out. Few, if any, practical multiband SWR meters
are any better than that.

I am immediately suspicious of any web site for an instrument that does not
have a bullet for "Specifications", but prominently advertises it can
customize the meter digital display with your Vanity Call!

It is an attractive meter, but I would not give it any special properties
over a good analog readout meter on a Bird Wattmeter.
73, Stuart K5KVH
Charles Greene
2002-10-16 06:01:31 UTC
Permalink
Larry and All,

I'm not disagreeing with you Larry, and here's a story to illustrate your
point. I recently built and tested a portable vertical in my yard for use
at a special event site in the field. The design of the antenna is not at
issue here so I won't get into it. I carefully tuned the antenna by
adjusting the length of the radials and radiator for a Z of 50 ohms and
resonance by measuring R + jX at the base of the antenna for the point at
which the X component crossed from + to -. BTW, this is not the point of
lowest SWR, but close to it. I was using an Autec VA1 which measures SWR,
R, X and a bunch of other stuff. On this meter you can't get X to read 0,
but it will jump from like a -8 ohms to a +8 ohms as you tune across the
resonant frequency. At this point the SWR read 1.02:1 at 14.2 MHz and R
read 49 ohms. I was using 84' of LMR-400 coax (50 ohm low loss stuff) in
series with about 16' of RG8X and an couple of antenna switches to the
rig. In the shack, the SWR read 1.14:1 at 14.2, and R was 58 ohms using
the VA1. My SWR/Power meter read an SWR of 1.0:1 in the shack. I couldn't
get it budge off zero reflected power. Now that SWR and R was nothing to
complain about and my K2 antenna tuner made short work of it, but I
wondered why the readings were not repeated in the shack. I attributed it
to the length of the coax. Then a couple days ago, I ran across an article
by Frank Witt, AI1H in ARRL Antenna Compendium, #4 entitled "Broadband
Matching Transmission Line Resonator." Basically what Frank was doing was
to "tune" the antenna system slightly by varying the length of the
transmission line, and thus broad banding it. In my case, I was detuning
the antenna system slightly (where the system is the combination of the
antenna and the transmission line) by using a random length of transmission
line. In order to get the same results in the shack as at the antenna you
need an electrical 1/2 wave transmission line or multiples there-of with
the same impedance as antenna. Morale of this posting: 1. Don't believe
your SWR meter, 2. Read Frank's article to see how varying the length of
the coax "tunes" your antenna system, and 3. As long as your SWR is low but
not exactly 1:1, don't worry about it as losses are low and the rig is happy.

Sequel to the story. At the special event site the environment was
different and the antenna resonance was way off. I retuned it by varying
the length of the radiator only as I didn't have time to vary the lengths
of the radials too, so the SWR at resonance was about 1.2:1. I didn't
bother to read the Z at the station as the SWR/power meter said 1:1 and at
this point in time I couldn't do anything about it. Morale to the
sequel: Don't spend too much time tuning a portable antenna at home as you
will probably have to redo it in the field anyway.
Post by Larry East
Post by sjolin
Changing the length of coax used
to feed an antenna will change the swr at the rig. I've seen cases where the
swr will change just by adding an extra couple feet of cable in the shack.
That is incorrect -- if your "SWR Meter" is indeed measuring SWR. The
complex impedance seen by the rig (or tuner) will change depending on the
length of coax, but not the "true" SWR. For an insight into this, read
Chapters 7, 8 and 9 in "Reflections II" by M. Walter Maxwell, W2DU. A most
illuminating book that should be read by every "technically oriented" ham...
73,
Larry W1HUE/7
PS - PLEASE lets DON'T start a big thread on SWR, complex impedances, etc.!
73, Chas, W1CG
K2 #462
Dave Larson
2002-10-15 13:35:01 UTC
Permalink
As the owner and user of one of the Sigma 5's that Hank refers to, let me
say that it is an outstanding antenna for dx work. It does, however, have a
low angle of radiation and would not be an antenna for emergency work for
that reason. Ted, K8AQM, and I made 7500 Q's in the 9 days we were in 5W0
using the 2 Sigma 5 antennas on 20 meters and up. We worked a large number
of QRP stations on RTTY, CW and SSB. We received many comments about how
loud we were. WE tuned the Sigma's so that we had a low SWR from 14.025 to
14.260 and stayed well below the 2:1 SWR given in the specs. I've made a
comparison from home (Michigan) comparing the Sigma to a R8 vertical and the
Sigma is the winner on DX but the R8 beats it for stateside. The Sigma 5
will be going with me on the next DXpedition.

Dave, K8AA 5W0DL
K2/100 #2657

----- Original Message -----
From: <***@ENTERZONE.NET>
To: "Hank Kohl" <***@arrl.net>
Cc: "Elecraft" <***@mailman.qth.net>
Sent: Tuesday, October 15, 2002 1:39 AM
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?
Post by k***@ENTERZONE.NET
Post by Hank Kohl
The Sigma5 is 20-17-15-12-10M with relay control to change bands.
A friend of mine used a couple of these on his last trip to the Pacific and
said they performed great.
Not bad for $349 and very portable.
73 Hank K8DD
I just looked at the site and it looks "interesting" except for the fact
that they claim 2:1VSWR over an adjustable 320Khz segment of 20m. Am I
just anal retentive of are there others out there that consider any
supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
antenna?
If I want 2:1, I can switch in most any of my antennas, on nearly any band
and get very close to 2:1 with no tuner. When it comes to resonant
antennas, I want to see 1.2:1 or better and will spend quite a bit of time
looking for as close to 1.0:1 when putting up an antenna.
My 75m antenna is 1.01:1 at 3.875 (one of my ragchew favs) and the 160m
loop is 1.03:1 at 1.898.
I consider an antenna that requires a tuner to operate at its design
frequnency with less than 1.5:1 to be a compromise at best. When the fit
hits the shan and I need to get on the air in an emergency, I don't want
to be twiddling with a tuner and I also don't want to risk blowing up the
amplifier.
Maybe I just think differently. To me, the transmatch, in the grand
scheme of things, is another potential point of failure when you're
DEPENDING on your communications equipment for emergency comm.
For ragchew, no problem. Twist some knobs, press the tune button, do
whatever it takes.
73 de John - KC4KGU
K2/100 #2490
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Tom Hammond NØSS
2002-10-15 14:14:00 UTC
Permalink
George just said EVERYTHING I wanted to say, and MUCH better than I could
have EVER said it.

Toward the end of his reply, George makes reference to Walt Maxwell's
"Reflections II", which, though I've not read it, I understand is as good
as his first book, "Reflections" which I HAVE read, but which is no longer
in print.

For anyone interested, an EXCELLENT intro to both of Maxwell's works is now
available at the ARRL web site. This is a PDF containing the contents of a
series of QST articles by Maxwell (W2DU), entitled "Another Look at
Reflections", which appeared in the early 70's. The series of articles was
never quite completed at that time, but regardless, they contain some of
the VERY BEST antenna theory you'll find anywhere. Even if you blow right
by the math (and it's certainly there if you choose to get 'into' it), the
articles are written so just about anyone will be able to gain a
significantly better understanding of antenna matching and SWR (which is
the crux of the series).

To access this article, go to http://www.arrl.org and in the SITE SEARCH
field at the top of the page, type in "ANOTHER LOOK AT REFLECTIONS" and
click on GO. Once the search returns its results, "REFLECT.PDF" should be
at the top of the list. RIGHT-CLICK on this link and then, when prompted to
do so, select SAVE FILE AS (or whatever similar choice you are presented by
your browser) and SAVE the file to your hard drive. DO NOT attempt to read
the article on-line by merely clicking ON the link and paging thru it. The
article's much too long to be viewed on-line.

This should be a "must-read" for all hams.

73,

Tom N0SS
Post by George, W5YR
John, I really don't know if you are anal retentive or not, but an antenna
can be resonant and still present a 10:1 SWR to the feedline.
The absolute magnitude of VSWR is not an indicator of resonance.
Resonance is solely, only and always the condition of a tuned circuit in
which the impedance at the port of interest is purely resistive or real.
The real component may NOT be the same as the Zo of a transmission line,
hence the SWR can be other than 1:1.
Resonance has nothing to do with SWR. SWR is determined solely by the ratio
of the driving point impedance of the antenna to the Zo of the transmission
line, or vice versa.
It is your choice to place so much emphasis on SWR but the facts are that
it is relatively unimportant to the actual radiation performance of an
antenna. An antenna fed with a line having any SWR will radiate all the
power it receives. If the line is low-loss, it can easily be the case that
more power is delivered to the antenna over a line with a 20:1 SWR than a
line with a 2:1 SWR. It is all a question of relative line loss, frequency,
line length, etc.
But the resonance or lack thereof of the antenna has very little to do with
it. Every antenna that I use, except for my Butternut HF9V vertical, is
non-resonant in any amateur band. They all work great on 80 through 10
meters, and most of my operating is QRP CW where efficiency counts.
With all respect, John, a review of the Antenna Book on the topics of
antenna resonance might be worth your time. Walt Maxwell's "Reflections II"
will give you an entirely new outlook on this subject. Resonance is
convenient for matching purposes, but that is about all it buys for you.
Mike McCoy
2002-10-15 14:59:00 UTC
Permalink
If you're like me, most antenna theory seems to be presented in a rather
mind numbing and overly complicated manner. Here is a good site (i.e.
presented straightforward and simply) about the basics of L, C, Q,
resonance, reactance, impedence, etc. :

http://my.integritynet.com.au/purdic/electronic-basics.htm

Mike - AD5IU
Stuart Rohre
2002-10-15 20:20:01 UTC
Permalink
And the other great web site for antennas basics and applications:
L. B. Cebik's W4RNL continuing efforts at www.cebik.com
72, Stuart K5KVH
Stuart Rohre
2002-10-15 22:18:00 UTC
Permalink
When a manufacturer gives a spec such as 2:1, over a range of the band, the
antenna as others have said, can be 1:1 at some spots and perhaps 2:1 at the
ends, depending on local conditions as well. I have operated the Sigma 5 by
Force 12 at ideal conditions on a Salt water beach, some 50 feet from the
surfline, and at NO time did it ever reach 2:1! It was a joy to operate and
had band switching. Did not need the rig tuner to move around the band.
72, Stuart K5KVH
Mike McCoy
2002-10-15 22:42:03 UTC
Permalink
Post by Stuart Rohre
I have operated the Sigma 5 by
Force 12 at ideal conditions on a Salt water beach, some 50 feet from the
surfline, and at NO time did it ever reach 2:1! It was a joy to operate and
had band switching. Did not need the rig tuner to move around the band.
72, Stuart K5KVH
Well I don't believe it.

I can see right now that when I finally get the Sigma 5 I will just have to
make a trip to the Caribbean to test it.

Mike - AD5IU
Don Brown
2002-10-15 18:08:01 UTC
Permalink
Hi George

This reminds me of a DMM made by Tektronix with a display of 4 1/2 digits=
but an accuracy spec of 0.1% The last digit is for all practical purpose=
s useless. In fact one of the technicians placed a little sticker over th=
e last digit so he could not see it on the meter at his bench. =20

Some times people take the readings too seriously on their test equipment=
and forget the specifications. Just because it has a nice digital readou=
t does not mean it is as accurate as it might appear. As you know RF watt=
meters (and SWR meters) are not very accurate. Within a few percent is q=
uite good (the industry standard is the Bird with 5%) - nowhere near as a=
ccurate as any of the cheapest DMM's are when measuring DC or resistance.=
Does it really mater, NO because the type of measurements made with watt=
meters, a small amount of inaccuracy probably won't matter.


Don Brown
KD5NDB


----- Original Message -----
From: George, W5YR
Sent: Tuesday, October 15, 2002 11:26 AM
To: ***@enterzone.net
Cc: ***@mailman.qth.net
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?


<SNIP>
Post by John Fraizer - KC4KGU
=20
RF Applications VFD http://www.rfapps.com/vfd.htm
I note that no accuracy specification is given at the URL for your unit.
Rather they ask you to "compare with the Bird 43 . . ." The Bird is rated
at +/- 5% of full scale. If you will work with that accuracy figure and g=
o
through the equations for computing VSWR from forward and reflected power
measurements - which is what your instrument does wioth its microcomputer=
-
you will find that there is no way that it could actually compute the
difference between a 1.01 and a 1.03 SWR. The instrument may well display
such readings, but they are an artificial artifact of the processing, not
reflective of the accuracy of the raw power data. =20

<SNIP>


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Bob Lewis (AA4PB)" (Bob Lewis (AA4PB))
2002-10-15 19:43:01 UTC
Permalink
Post by Don Brown
Some times people take the readings too seriously on their test
equipment and forget the specifications.
Same goes for that nice digital frequency readout on the transceivers.
The least significant digits mean nothing in most cases, other that
short-term resettability. Especially true if you haul it out into the
field where ambient temperatures vary.
Mark J. Dulcey
2002-10-15 21:23:00 UTC
Permalink
This reminds me of a DMM made by Tektronix with a display of 4 1/2 digits but an accuracy spec of 0.1% The last digit is for all practical purposes useless. In fact one of the technicians placed a little sticker over the last digit so he could not see it on the meter at his bench.
The limited accuracy spec doesn't make that last digit entirely useless. If you're nulling or peaking something, the extra digit might allow you to do so more precisely; the fact that the absolute value on the display isn't accurate isn't relevant. On the other hand, if the instrument isn't monotonic to 4 1/2 digits, then that last digit will do you no good at all - but you didn't say whether that was true or not.
Don Brown
2002-10-15 22:30:01 UTC
Permalink
Hi

Actually the A to D was that good (.01%) but they only used .05% divider =
resistors so the spec is only as good as the divider, and .05% is only 3 =
1/2 digits. You are right about the nulling or peaking, as well as you co=
uld make relative measurements


Don

----- Original Message -----
From: Mark J. Dulcey
Sent: Tuesday, October 15, 2002 3:23 PM
To: Don Brown
Cc: George, W5YR; ***@enterzone.net; Elecraft
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?
=20
This reminds me of a DMM made by Tektronix with a display of 4 1/2 digi=
ts but an accuracy spec of 0.1% The last digit is for all practical purpo=
ses useless. In fact one of the technicians placed a little sticker over =
the last digit so he could not see it on the meter at his bench. =20

The limited accuracy spec doesn't make that last digit entirely useless. =
If you're nulling or peaking something, the extra digit might allow you t=
o do so more precisely; the fact that the absolute value on the display i=
sn't accurate isn't relevant. On the other hand, if the instrument isn't =
monotonic to 4 1/2 digits, then that last digit will do you no good at al=
l - but you didn't say whether that was true or not.


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multipart/alternative
text/plain (text body -- kept)
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k***@juno.com
2002-10-15 22:44:01 UTC
Permalink
Larry, W1HUE/7 wrote:

"If one uses a "reflectometer" to measure forward and reflected power on
a relatively loss-less transmission line, it matters not where the
measurement is done along the transmission line -- one will still get the
correct SWR."
==========
True only if the antenna is matched to the feedline, i.e., the SWR is
1:1.

If the SWR is higher, then the minimum SWR reading is correct (depending
on the accuracy of the meter) only if the meter is placed in the feedline
at a multiple of 1/2 waves from the antenna.

73, de Earl, K6SE
Bob Lewis (AA4PB)" (Bob Lewis (AA4PB))
2002-10-15 23:18:01 UTC
Permalink
the minimum SWR reading is correct only if the meter is placed in
the feedline
at a multiple of 1/2 waves from the antenna.
Given no significant loss in the transmission line, what accounts for
the SWR changing as you insert the meter at different points in the
line? It seems to me that the power reflected by the mismatched load
would be the same all along the line, except for the amount dissipated
by the loss in the line.
Bob Lewis (AA4PB)" (Bob Lewis (AA4PB))
2002-10-15 23:51:01 UTC
Permalink
I think this is what happens. The SWR anywhere along the line is
constant and is determined by the ratio between the characteristic
line impedance and the load impedance. The impedance (not the SWR)
along a mismatched transmission line varies with distance from the
load, repeating every 1/2 wavelength. Most of the inexpensive VSWR
meters we use are only accurate when placed in a 50 ohm line. As you
move the meter to different points along the line you get different
"SWR readings" because of the errors in the instrument when presented
with different impedances. With a good reflected power meter you
should get the same ratio of forward to reflected power (and thus SWR)
anywhere along the line. All of this assumes zero transmission line
loss. Any line loss acts on both the forward and the reflected power.
At the transmitter the forward power is not attenuated while the
reflected power is attenuated twice (up to the antenna and back) so
the ratio looks better at the transmitter than it does at the antenna
end of the line. So, if you have any significant amount of
transmission line loss then you should insert the meter at the antenna
to get the most accurate reading.
Stuart Rohre
2002-10-16 20:51:01 UTC
Permalink
The process Bob describes will work with meters such as Bird Wattmeter, that
read actual forward and reflected power. Then use a chart of power ratio vs.
SWR to find the actual SWR.

Use of other general purpose SWR type meters should be confined to the rig
side of the tuner, in the 50 ohm coax line, for which they were designed.
They may give widely varying results otherwise.
72, Stuart K5KVH
George, W5YR
2002-10-15 23:52:00 UTC
Permalink
That is correct, Bob . . . this is another instance of confusing SWR
readings with impedance readings. This admonition is frequently found in
the CB literature . . .

In a practical situation, if there is common-mode current on the coax outer
braid, then the "indicated" SWR reading from the typical reflectometer type
of SWR meter will in fact vary with position in the line.

But, in the absence of CM current, the only effect on SWR readings from
proper instrumentation would be assigned to loss in the transmission line.

A contrived situation can be created in which the SWR reading *does* vary
with position but it requires use of a very lossy transmission line having
a complex Zo and an SWR instrument whose reference impedance does not match
that of the line. This is not a combination very likely to be found in an
amateur station installation.

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489 Icom IC-765 #2349 Icom IC-756 PRO #2121
Post by sjolin
the minimum SWR reading is correct only if the meter is placed in
the feedline
at a multiple of 1/2 waves from the antenna.
Given no significant loss in the transmission line, what accounts for
the SWR changing as you insert the meter at different points in the
line? It seems to me that the power reflected by the mismatched load
would be the same all along the line, except for the amount dissipated
by the loss in the line.
Larry East
2002-10-16 00:23:00 UTC
Permalink
Post by Bob Lewis (AA4PB)" (Bob Lewis (AA4PB))
Given no significant loss in the transmission line, what accounts for
the SWR changing as you insert the meter at different points in the
line?
A bad meter! :-)
Post by Bob Lewis (AA4PB)" (Bob Lewis (AA4PB))
It seems to me that the power reflected by the mismatched load
would be the same all along the line, except for the amount dissipated
by the loss in the line.
That is absolutely correct. Those in doubt should read the book
("Reflections II").

L.
k***@juno.com
2002-10-16 04:31:00 UTC
Permalink
Bob, AA4PB wrote:

"I think this is what happens. The SWR anywhere along the line is
constant and is determined by the ratio between the characteristic line
impedance and the load impedance. The impedance (not the SWR) along a
mismatched transmission line varies with distance from the load,
repeating every 1/2 wavelength. Most of the inexpensive VSWR meters we
use are only accurate when placed in a 50 ohm line.

As you move the meter to different points along the line you get
different "SWR readings" because of the errors in the instrument when
presented with different impedances. With a good reflected power meter
you should get the same ratio of forward to reflected power (and thus
SWR) anywhere along the line."
----------
Bob expresses my point much better here than I did. My previous post was
in response to what Larry, W1HUE/7 said about reflectometers.

Most run-of-the-mill cheap reflectometers used by hams are not reliable
for accurate measurement of SWR. That was my point in stating that the
best place for these devices for reasonable accuracy is at a multiple of
a half-wave along the line from the feedpoint.
==========

"All of this assumes zero transmission line loss. Any line loss acts on
both the forward and the reflected power. At the transmitter the forward
power is not attenuated while the reflected power is attenuated twice (up
to the antenna and back) so the ratio looks better at the transmitter
than it does at the antenna
end of the line. So, if you have any significant amount of transmission
line loss then you should insert the meter at the antenna to get the most
accurate reading."
----------
Absolutely true. Since no line is lossless, this also makes the antenna
appear to be broader-banded than it really is. The plus side is that the
transmitter "thinks" it is looking into a lower SWR, so it's happier.

73, de Earl, K6SE
k***@juno.com
2002-10-16 06:01:15 UTC
Permalink
As Bob, AA4PB stated, changing the length of the feedline can drastically
change the measured R and X on the end of the line if the SWR is high,
resulting in inaccurate SWR readings on a fixed-impedance 50-ohm SWR
meter.

A good example is where you have an antenna whose feedpoint is about 100
ohms unbalanced. If you feed it with a 3/4-wavelength of 75-ohm coax,
your 50-ohm SWR meter will read a 2:1 SWR at the feedpoint, but it will
read 1:1 SWR at the other end of the coax. This is due to the ability of
a 1/4-wave length of coax to transform the impedance and the ability of
a 1/2-wave of coax to repeat the impedance seen at its other end.

For Larry, W1HUE/7, who told me in a personal e-mail to "read the book",
I resent that snide remark. The above paragraph describes exactly what I
meant in my original post (that reliable measurements are only made at
multiples of a half-wave from the feedpoint). I suggest that YOU re-read
the book, Larry!

The handiest instrument I've found for accurate measurement of SWR is the
Autek model VA-1 Vector RX Antenna Analyst. It has a feature where you
can enter the length of the feedline and the instrument compensates for
this length and calculates the antenna R and X as (and therefore the SWR)
as it would actually be if measured at the feedpoint of the antenna.
(Why would they have that feature if the instrument measured the same SWR
anywhere on the line?)

The meter also has a menu whereby you can select virtually any
characteristic line impedance from 25 to 450 ohms, so it's not restricted
to 50 ohms like most meters.

73, de Earl, K6SE
k***@ENTERZONE.NET
2002-10-16 16:32:01 UTC
Permalink
Post by Stuart Rohre
The Bird meter this meter is compared to, carries manufacturers specs of 5
per cent as George pointed out. Few, if any, practical multiband SWR meters
are any better than that.
I am immediately suspicious of any web site for an instrument that does not
have a bullet for "Specifications", but prominently advertises it can
customize the meter digital display with your Vanity Call!
It is an attractive meter, but I would not give it any special properties
over a good analog readout meter on a Bird Wattmeter.
73, Stuart K5KVH
You haven't used one. There is only one piece of equipment that I have
ever owned that I would recommend with as much enthusiasm and that is the
K2.

The VFD has an autoscaling "VU" type display when it sees RF. This makes
tuning an amplifier or a transmatch go very quickly. I have a very nice
crossed-needle VSWR bridge but, I look at the VFD because it's quicker.

In addition, the VFD has an SWR alarm that lights a high-intensity red LED
as well as provides a SPDT relay output. Put this in line with your
PTT/key line or your amplifier keying line and you have auto-shutdown in
the event that something catastrophic happens to your antenna system or
transmission line while you're operating. The SWR that indicates an alarm
is user selectable.

In addition, the VFD is excellent for working in low light conditions. My
bird doesn't have a backlight and I don't even think they have a model
that does. Kinda useless if you can't see it.

Anyway, like I said, I like it, I recommend it. It is a very nice piece
of equipment and it has saved my equipment once already when I had a
catastrophic antenna system failure caused by a tree falling during mid
QSO. Since my shack is in the basement, I would have had no idea and with
no "in your face" light and "rig stops keying, amp key circuit disabled
down" action on on the bird, I would not have known about the antenna
problem until it was too late.


73 de John - KC4KGU
K2/100 #2490
Elecraft WAS #8
Vic Rosenthal
2002-10-16 16:54:01 UTC
Permalink
Regarding the VFD digital SWR/power meter, I have one it and it does have some
very nice features. I use the SWR alarm relay to protect my solid-state amp and
I like the readability of the display.

But (there's always a 'but'): the unit has a 3KW full-scale. I suspect that in
order to get such a wide range the designer sacrificed accuracy at the very
bottom end; mine is pretty inaccurate below about 15 watts.

So if you are interested in QRP you probably should also have one of those nice
OHR units or a Bird with several slugs.

Vic K2VCO
Stuart Rohre
2002-10-16 21:41:01 UTC
Permalink
The VFD has lots of features for the fixed station running high power, but
the Bird requires NO AC nor Batteries.

For QRP at the most popular levels of 5 watts, and 10 w pep ssb, there is an
excellent value kit power meter.

A very good, and calibration easy meter for QRP use is the Ten Tec T kit SWR
Power Meter. Mine was $49.95, and an easy build from an excellent manual.
They may have gone up a bit, but still are an excellent buy.

To convert from 20 watt scale to 2 watt scale, I just turned a calibration
pot, to make a known power of 2 watts read that. The scales can be 20w or
200 w as built, unless you recalibrate. It does need one 9 volt battery,
but has low drain. It also has pickups for both HF and for VHF/UHF.
Although not sold as a 440 MHz unit, I found it works fine for finding a
good
swr null with 440 equipment.

72, Stuart K5KVH
Steve Lawrence
2002-10-17 14:18:01 UTC
Permalink
Mike,
When this antenna arrives, and you've had some operating time on it, how
'bout a report to the group?

I too have been looking a verticals -- and have observed the same thing:
1/2 love them, the rest hate them! It doesn't matter if it's a Gap,
Butternut, Hustler, Cushcraft, .... Then some fixate on their "low SWR"
which probably means "high loss"... The amount of misunderstandings
concerning verticals is simply overwhelming. Then, just start a
conversation about radials: how many, buried? elevated? bare wire?
insulated? it goes on and on! Objective, controlled experiments are
simply hard to find.

Then comes Force 12. No nonsense, clearly center fed vertical, doesn't
seem to rely on some "magic" (or marketing BS?) to work in contradiction
to the laws of nature. But I haven't read many reports on the Sigmas or
comparisons to say, a dipole at 30' (a common, practical antenna
installation).

So, let us know?

73,
Steve
aa8af





"Mike McCoy" <***@austin.rr.com>
Sent by: elecraft-***@mailman.qth.net
10/14/2002 08:01 PM


To: "Elecraft" <***@mailman.qth.net>
cc:
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?


Well I broke down and ordered a Force 12 Sigma GT5 (no-trap/no radial
vertical dipole) today.

Since I have no horizontal space for a dipole I've been investigating
verticals for a while. The thing that has put me off (aside from the need
to
plant radials) is that for virtually every vertical manufacturer it seems
1/2 of owners love em and the other 1/2 can't get rid of them fast enough.

Except for Force 12... I haven't heard one person say anything (really)
negative about Force 12 antennas. And apparently they can't keep the Sigma
5
in stock (backordered 3-4 weeks).

And here's a very interesting new antenna from Force 12 just now
available,
a 16' 40-10 vertical dipole:

http://force12inc.com/sigma40XKinfo-001.htm

Not bad for $249...

Mike - AD5IU
Stuart Rohre
2002-10-18 21:25:01 UTC
Permalink
Steve and the group, be careful in trying to compare ANY vertical to a
dipole.

They are really for differing applications. The dipole at 30 feet high,
will work more close in stations locals, and short hop, say on 40m. On the
bands 20m and up it will be good for DX in the two directions a dipole works
broadside to the wire. It will be of limited utility at 30 feet for 80m,
even if long enough there.

The vertical is an omnidirectional antenna. If there is DX in any
direction, it should hear and work it, as it favors low take off angles if
its vertical dimension is a substantial fraction of a half wave or quarter
wave at the band in use. IF a quarter wave type, it HAS to have SOMETHING
to replace the other missing half of the antenna. The near half wave
verticals can do that, without added radials, or ground screen in near field
below. The quarter wave must have help be it radials, elevated or ground,
or a plane or screen.

The vertical is mainly a low angle radiator, but can under conditions all
the time work close in stations but perhaps without as strong a signal as a
horizontal. That is because the horizontal wastes some signal in terms of
DX working with overhead radiation, but that same overhead lobe, is what
gives high angle ability to reach close in stations with good signals. The
vertical has little radiation off its end, if of the classic type, much as
the dipole has little radiation off its end. In the case of the vertical,
you lose ONLY the overhead direction, while the dipole loses two directions
off the ends.

The real answer is you need both a dipole and a vertical for a good
combination of high angle capability for in state, or close state work, and
low band work, and the vertical for DX. The vertical, if a good one, is
the cheapest DX antenna other than a very large Vee Beam, or Horizontal
Loop, which few have the real estate to put up save perhaps for 10m. Those
need to be 2 waves at least, and that would be 64 feet at 10m, doable on a
city lot, but barely. If you must have low profile, a vertical behind the
privacy fence and behind the house, will have lowest profile from the
street, unless you have enough trees to hide a horizontal or loop. Don't
give up on having an inverted Vee, if you still need stealth antennas. I
know a ham who hung one within a large tree he had in back yard, and it was
with such smaller wire and insulators that it was not seen from outside his
yard, but worked well on the lower bands where Inv. Vees are commonly used.
Insulators for those can be small pvc pipe couplings, or sections, or small
vitamin plastic bottles.

If you could only have one antenna, and it most be low profile, I would
first go with a vertical. IF you could get a horizontal up half wave high,
then that would be my first choice. At 30 feet, I would go with the
vertical. A 30 foot vertical will give a good account of itself on 40m and
up, if made for all those bands.
73, Stuart K5KVH
k***@juno.com
2002-10-18 22:18:01 UTC
Permalink
Stuart, K5KVH wrote:

"IF a quarter wave type, it HAS to have SOMETHING to replace the other
missing half of the antenna. The near half wave verticals can do that,
without added radials, or ground screen in near field below. The quarter
wave must have help be it radials, elevated or ground, or a plane or
screen."
==========
While I agree with the rest of Stuart's post, I must take exception with
his statement about 1/2-wave verticals (either dipoles or end-fed) and
elevated radials.

One of the most common misconceptions is that a low 1/2-wave vertical
does not need radials. If a good radial system is not placed on the
ground below this antenna, the same amount of energy heats up (is lost
in) the ground just as much as it would with a 1/4-wave vertical. The
only way around the ground loss problem is to make the center of the
vertical at least 1/2-wave above ground, and preferably much higher.

The same is true about a 1/4-wave vertical with elevated radials (unless
there are as many radials as there would be if the vertical was
ground-mounted). Many hams on 160m use only 4 elevated radials 10 feet
high or less, thinking it will work as good as an on-ground system with
60 radials. 10 feet is less than 0.02 wavelength on 160m, so those 4
radials act the same as if they were on the ground or buried, therefore
the same ground losses apply for the "elevated" system, so the ham using
a low, elevated radial system is disappointed in the results compared to
those who use extensive ground radial sustems under their verticals.
Although the antenna will work, most of the power is lost in the ground.
This has been proven by far-field field strength measurements by others
who have investigated on-ground versus elevated radial systems.

For a 4-radial elevated system to be any good, it must be *at least*
1/4-wave high. Even at that height the antenna efficiency suffers due to
ground loss.

Ground screens have also been investigated. While they are ok if they
extend away from the base of the vertical as far as an extensive radial
system would, the radials are still better (and far less expensive).

73, de Earl, K6SE
Stuart Rohre
2002-10-18 22:54:00 UTC
Permalink
Thanks for the comments Earl. I got to typing too fast and should have
included the following:

I should have clarified that extensive modeling work by L. B. Cebik, W4RNL,
and published by him at his www.cebik.com web site, shows that CENTER FED
vertical dipoles, at the heights he modeled, do not show much effect from
the addition of ground screen under them. I refer those with questions to
L. B.'s excellent web comments upon this point. He has been right on with
all his modeling, and I know from personal correspondence, he checks things
with all the available programs, even the professional ones, not ordinarily
available to hams.

The bottom fed half wave, as Earl reports, certainly might suffer earth
loss. I have not seen modeling for this case as yet. (End feed, with and
without added ground under it). I have not been worried about small
improvements less than a dB or 2, but certainly, some might feel those
should be pursued.

Most antennas would benefit by improved RF earth in the Fresnel Zone, but
that is out of hams control in most locations, being some 2 to 5 wave
lengths away from the antenna. But, this area is the one you can somewhat
control by locating your antenna on the edge or top of a high location.

vertical dipoles, (center fed), are an underexplored resource available to
hams for 20m and up, and in the capacitance hat loaded forms now being
offered, for 40m and up. My work with 5 band models has been most
encouraging, and our lab has acquired some more from Force 12 for our HF
experiments. I hope to build an all band model without loading coils myself
to see if there is good improvement from that effort. I would hope to use
parallel vertical dipoles supported by the one for the lowest band. Sleeve
feed would be possible it seems with such an arrangement. That works well
in beams and horizontal antennas thus should be a natural for the home made
vertical.
73, Stuart K5KVH
Jason Hissong
2002-10-19 01:20:05 UTC
Permalink
I have been following this thread with some interest. I just bought a
Hexbeam and will be getting a WindomHSQ. The Hexbeam will be up about 32'
(I could go higher if I got the 26' roof mounted tower instead.) The Windom
will be mounted at about the 30' mark (center supported). That way, I could
get the benefits of the beam, local stuff with the dipole. I guess my
question is, would getting a vertical also be beneficial? I have no means
to get on 80 and 160 with that antenna configuration. I have about 70 feet
between two trees. Both of which I may be able to get a flat top at 30
feet.

Was thinking about the Bencher (Butternut) 2 band antenna with the 30 and
160 meter kits.

Thanks!

Jason Hissong
N8XE
----- Original Message -----
From: "Stuart Rohre" <***@arlut.utexas.edu>
To: <***@mailman.qth.net>; <***@juno.com>
Sent: Friday, October 18, 2002 5:43 PM
Subject: Re: [Elecraft] HF Verticals?
Post by Stuart Rohre
Thanks for the comments Earl. I got to typing too fast and should have
I should have clarified that extensive modeling work by L. B. Cebik, W4RNL,
and published by him at his www.cebik.com web site, shows that CENTER FED
vertical dipoles, at the heights he modeled, do not show much effect from
the addition of ground screen under them. I refer those with questions to
L. B.'s excellent web comments upon this point. He has been right on with
all his modeling, and I know from personal correspondence, he checks things
with all the available programs, even the professional ones, not ordinarily
available to hams.
The bottom fed half wave, as Earl reports, certainly might suffer earth
loss. I have not seen modeling for this case as yet. (End feed, with and
without added ground under it). I have not been worried about small
improvements less than a dB or 2, but certainly, some might feel those
should be pursued.
Most antennas would benefit by improved RF earth in the Fresnel Zone, but
that is out of hams control in most locations, being some 2 to 5 wave
lengths away from the antenna. But, this area is the one you can somewhat
control by locating your antenna on the edge or top of a high location.
vertical dipoles, (center fed), are an underexplored resource available to
hams for 20m and up, and in the capacitance hat loaded forms now being
offered, for 40m and up. My work with 5 band models has been most
encouraging, and our lab has acquired some more from Force 12 for our HF
experiments. I hope to build an all band model without loading coils myself
to see if there is good improvement from that effort. I would hope to use
parallel vertical dipoles supported by the one for the lowest band.
Sleeve
Post by Stuart Rohre
feed would be possible it seems with such an arrangement. That works well
in beams and horizontal antennas thus should be a natural for the home made
vertical.
73, Stuart K5KVH
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Stuart Rohre
2002-10-19 01:49:04 UTC
Permalink
With the Hexbeam, which as I understand is a varient of the Moxon Rectangle,
or the VK2BQW, you have a potential low angle radiator with gain, and front
to back ratio. No reason to add vertical, unless Hex does not live up to
its billing. The vertical would not have gain, unless, (and you could)
phase two verticals. Make one a director, and lightweight material, and
walk it around to various locations supporting it with a T fence post and
short mast, (elevating the fed vertical), and ergo a vertical beam.

Why not just make a dipole for the 70 foot space, and mount it below (or
beside), the Windom a few feet, and droop both ends, so it can be closer to
full length half wave dipole for 80m? It will also load on 160 m with low
loss if fed with 450 ohm ladder line. A dipole can be shortened to 60 per
cent and still work with nearly full efficiency. Transmatch can make it
work on lowest band. That way, you could get 110 foot dipole in 70 foot
length. A full size 80m is only about 130 foot. Make it of no. 14 solid
pvc insulated wire from Home Depot.

Please let us know how the Hexbeam works re DX.
73, Stuart K5KVH
k***@juno.com
2002-10-19 00:19:00 UTC
Permalink
Stuart, K5KVH wrote:

"I have not been worried about small improvements less than a dB or 2,
but certainly, some might feel those should be pursued."
==========
Dean Straw (N6BV), who is ARRL's antenna guru, used NEC-4 (which can
model buried radials) to compare the efficiency of various radial
systems.

His modeling showed that for a system of four 1/4-wave radials on 80m in
or over "very poor" ground, about 4.75 dB of the power being applied to
the antenna was dissipated in ground losses.

Increasing to sixty-four 1/2-wave radials reduced the ground loss to
about 1.50 dB.

Over "average" ground, the 4 radials resulted in about 1.75 dB loss, and
64 radials had about 1.0 dB loss.

The moral of this story is that you should pick a site with high soil
conductivity for your vertical (where the number of radials is less
important).

Now we know why maritime mobiles with their salt water ground are so loud
on the low bands. And it explains why a balloon-supported 160m vertical
over a moist salt lake bed easily outperforms mountain-top 4-square
vertical arrays (which dispells the fallacy that mountaintop QTH's are
better for HF or MF DXing).

73, de Earl, K6SE
Stuart Rohre
2002-10-19 01:38:01 UTC
Permalink
Earl, there have been a number of papers on improved radio locations from
operating from elevated ground. I wish I could remember the paper, but
there is one I have seen with the ray traces to show the signals
improvement.
The signal can go from the antenna toward ground, but if on a hill, the
reflection happens at lower ground and they get a nice low angle of takeoff
on the reflection, lower than the flat ground case.
Locally, NT5C has had much good success from his hill, compared to my valley
location.

The paper I remember, had both operating measurements and modeling of the
paths, supported by the operational experience. Sorry I cannot remember
where I saw it, but might be QST or CQ, or QEX, even Communications
Quarterly.

We see the same thing in sonar measurements off reflections in a depression
below the sonar source.
It is proven Physics.
73, Stuart K5KVH


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Charles Greene
2002-10-19 13:25:00 UTC
Permalink
Hi All,

Anyone contemplating the use of elevated radials should read the article by
Dick Weber K5IU in Spring 1997 Communications Quarterly. Basically, Dick
points out that 1/4 wavelength is the length to be avoided in elevated
radials. This is because the impedance of resonant radials is zero, and
the current distribution in the radials is very uneven and one radial hogs
the current, drastically modifying the radiation pattern. He recommends
using radials of less than 60 degrees or more than 120 degrees to increase
the impedance of the radials so that a minor variation in the impedance of
one radial will not affect the current distribution. Moxon covers the
subject of elevated radials and recommends using shortened radials with a
common loading coil to tune them to resonance. He also states that the
resonance length of 1/4 is the one to be avoided. Other authors such as
ON4UN recommend the same approach. I have experimented with non resonance
radials by making the radials short and increasing the length of the
vertical element to tune the system to resonance, and by making the radials
long and the vertical element short to tune the system to resonance. The
reactance of the non resonant radials cancels the reactance of the vertical
element so that the entire system is resonant. This may be covered in the
literature somewhere but I haven't found it. I got the idea from KC1SD who
has been using it for years for 20 and 40 meter portable elevated radial
verticals for field day. The principle here is the same principal in use
with an off-center-fed horizontal antenna to a lesser degree. I have found
you can't depart very far from the resonant length of either the vertical
or radial element. The antenna resistance at resonance with short radials
and a long vertical is greater than 36 ohms, and the resistance of the
antenna with long radials and a shortened vertical element is less than 36
ohms. I have found this in the modelling and verified it with the actual
antenna. Modelling shows the longer vertical element has a fraction of a
dB more gain than the shorter vertical element, as to be expected. I have
modelled the system using an inductance to tune short radials as
recommended by Moxon, and have also modelled placing the inductor half way
up the vertical element to tune the system. The latter configuration shows
more gain (less loss) than the former for the same reasons that a
mid-loaded vertical has less loss than a base loaded vertical. KC1SD and I
have been using 2 elevated radials. The model shows they work as well as a
system with more. The model shows a surprisingly asymmetrical pattern with
only two elevated radials, which of course is an advantage for
portables. My current project uses two long radials and a shortened
vertical element. The radial were elevated only 1' here at home, but they
were on the edge of a 8' sea wall on the shore of Narragansett Bay. At the
special event site, I used the same vertical but elevated the radial to
7.5' so that people could walk under them. There was a good bit of
retuning required from the antenna with 1' elevated and the 7.5' elevated
radials.
Post by Ron D'Eau Claire
In the Ham literature, there is an excellent article by Al Christman,
KB8I, "Elevated Vertical Antenna Systems, published in the August, 1988
QST. That article also appeared in the ARRL publication, "Vertical
Antenna Classics". This article is a Ham-oriented version of Christman's
"Vertical Monopoles with Elevated Ground Systems," published in the
Proceedings of the Third Annual Review of Progress in Applied
Computational Electrodynamics by the Naval Postgraduate School,
Monterey, CA, March 1987.
H. L. Ley, Jr., N3CDR, did some very enlightening and interesting
experiments comparing a short loaded counterpoise to an elevated ground
system. He published his findings in "A Multiband Loaded Counterpoise
for Vertical Antennas" that appeared in "The ARRL Antenna Compendium,
Vol. 2" as well as in "Vertical Antenna Classics".
Ron AC7AC
K2 # 1289
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73, Chas, W1CG
K2 #462
Charles Greene
2002-10-19 12:05:00 UTC
Permalink
Stuart and All,

There is a treatment of elevated ground in Moxon, chapter 10. It is also
covered in the ARRL Antenna Book , chapter 3. There is an article in The
Antenna Compendium #6, page 89 which uses ray tracing much like sonar on
the path from Hawaii to Ca on 14 meters, but this is far field and has
nothing to do with elevated locations.
Post by Stuart Rohre
Earl, there have been a number of papers on improved radio locations from
operating from elevated ground. I wish I could remember the paper, but
there is one I have seen with the ray traces to show the signals
improvement.
The signal can go from the antenna toward ground, but if on a hill, the
reflection happens at lower ground and they get a nice low angle of takeoff
on the reflection, lower than the flat ground case.
Locally, NT5C has had much good success from his hill, compared to my valley
location.
The paper I remember, had both operating measurements and modeling of the
paths, supported by the operational experience. Sorry I cannot remember
where I saw it, but might be QST or CQ, or QEX, even Communications
Quarterly.
We see the same thing in sonar measurements off reflections in a depression
below the sonar source.
It is proven Physics.
73, Stuart K5KVH
73, Chas, W1CG
K2 #462
Stuart Rohre
2002-10-21 21:45:01 UTC
Permalink
Some private emails to me have suggested the work I most had in mind was
done from out west, Wash. or Oregon. Perhaps in the Adventure Radio Society
publication, and also QRPp or Colorado QRP magazine.
72,
Stuart K5KVH

Ron D'Eau Claire
2002-10-19 02:42:05 UTC
Permalink
Earl, there have been a number of papers on improved radio locations
from operating from elevated ground. I wish I could remember the paper,
but there is one I have seen with the ray traces to show the signals
improvement. 73, Stuart K5KVH

----------------------

In the Ham literature, there is an excellent article by Al Christman,
KB8I, "Elevated Vertical Antenna Systems, published in the August, 1988
QST. That article also appeared in the ARRL publication, "Vertical
Antenna Classics". This article is a Ham-oriented version of Christman's
"Vertical Monopoles with Elevated Ground Systems," published in the
Proceedings of the Third Annual Review of Progress in Applied
Computational Electrodynamics by the Naval Postgraduate School,
Monterey, CA, March 1987.

H. L. Ley, Jr., N3CDR, did some very enlightening and interesting
experiments comparing a short loaded counterpoise to an elevated ground
system. He published his findings in "A Multiband Loaded Counterpoise
for Vertical Antennas" that appeared in "The ARRL Antenna Compendium,
Vol. 2" as well as in "Vertical Antenna Classics".

Ron AC7AC
K2 # 1289
k***@juno.com
2002-10-19 04:12:01 UTC
Permalink
Ron, AC7AC wrote:

"In the Ham literature, there is an excellent article by Al Christman,
KB8I, 'Elevated Vertical Antenna Systems', published in the August, 1988
QST."
==========
Although KB8I is much respected, especially for his papers on phasing
systems he developed for vertical antenna arrays, his work on elevated
radial systems has been much discussed and questioned on the topband
reflector.

I mentioned in an earlier post that far-field field strength tests were
done to end the debate on whether elevated radials were any better than
buried radials. These tests were done by Tom Rauch, W8JI, who is one of
our most knowledgable AM BC engineers. Knowing Tom, I'm sure that the
tests were very well controlled and honest. Anyway, the field strength
measurements taken at a mile or so away from the antenna in all
directions, proved that elevated radials 10' high have no advantage over
the same amount of buried radials.

73, de Earl, K6SE
Paul Womble
2002-10-19 04:19:01 UTC
Permalink
I would want to see the results from Zone 26. Maybe Zone 34 for you Left
Coast guys. ;-)

Paul K4FB
Post by k***@juno.com
I mentioned in an earlier post that far-field field strength tests were
done to end the debate on whether elevated radials were any better than
buried radials. These tests were done by Tom Rauch, W8JI, who is one of
our most knowledgable AM BC engineers. Knowing Tom, I'm sure that the
tests were very well controlled and honest. Anyway, the field strength
measurements taken at a mile or so away from the antenna in all
directions, proved that elevated radials 10' high have no advantage over
the same amount of buried radials.
Stuart Rohre
2002-10-21 21:37:01 UTC
Permalink
One should never be too quick to say absolutes about radio propagation and
types of launching systems for the waves.

The pioneering work now being done by Dr. Robert L. Rogers on the FLEX
antenna, which does use resonant elements, but confined to much smaller
volume than their total length, has shown much promise for efficient tho
small antennas.

The type of Earth under an antenna can have many interactive effects.
Better ground may require more radials to avoid having currents lost to
earth, than those radials lying on poor ground.

There seems to be evidence that half wave antennas should operate virtually
independent of earth, but field strength measurements are also needed to see
if adding radials under them does anything. The complication is defining
the earth under the antenna adequately, as most practical installations are
over non homogeneous earth conditions. Near field objects in the practical
ham installation may greatly affect and alter what otherwise would be
optimum ways of using radials, ground reflectors, etc.

My own grounding tests in tropical Malaysia, and desert West Texas
undoubtedly are different from those in Northern U. S. The literature on
the use of quads in overseas locations often reports excellent results at
low heights, while there has been less favorable reports on quad vs. Yagi
tests on towers in U.S. About all we can say absolutely is there is no one
antenna "best" for all locations and conditions. Rarely have hams
considered they should match their antenna choice to local earth under the
proposed antenna, but my own experiments show I should have considered that
earth, and characterized it before picking some antennas I have used.
72,
Stuart K5KVH
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