Discussion:
KAT100 and external watt meter question
(too old to reply)
Glenn Maclean
2003-01-30 16:23:00 UTC
Permalink
I have a question as to what is the best way to use an external watt meter?
I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to connector
labeled TR on the external watt meter and then the antenna connected to
the connector labeled ANT on the external watt meter. I was getting a good
match according to the K2100 display and the KAT100 LED's. The external watt
meter however was showing high SWR on some bands especially 30 meters. On 40
meters and 20 meters the external watt meter, KAT100 and K2100 SWR displays
all agree. On other bands the external watt meter showed very high SWR. I am
using a Carolina 40 Windom antenna by Radio works.

I re-arranged the configuration of the watt meter by connecting the RF out
from the K2100 to the TR connector on the external watt meter. Then the ANT
connector on the external watt meter goes to RF in on the KAT100. Then I
connected the antenna to the ANT1 on the KAT100. I then went through the
bands. The KAT100 re-adjusted the settings on all bands. Now the external
watt meter shows matched power out readings compared to the K2100 display.
The SWR is low on all the bands according to the external watt meter, KAT100
and K2100. Is this the best way to have an external watt meter connected?

Thanks,
Glenn WA7SPY
Dave Gingrich K9DC
2003-01-30 16:43:01 UTC
Permalink
The short answer is Yes.

What you have proven here is that the antenna tuner does not really change
the characteristics of the antenna system. The SWR at the end of the coax
is unchanged (as indicated by the readings when your wattmeter was located
outside the tuner). The coupler simply adjusts for the mismatch as best it
can, trying to provide a 50 ohm load to the transceiver.

Dave K9DC
Post by Glenn Maclean
I have a question as to what is the best way to use an external watt meter?
I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to connector
labeled TR on the external watt meter and then the antenna connected to
the connector labeled ANT on the external watt meter. I was getting a good
match according to the K2100 display and the KAT100 LED's. The external watt
meter however was showing high SWR on some bands especially 30 meters. On 40
meters and 20 meters the external watt meter, KAT100 and K2100 SWR displays
all agree. On other bands the external watt meter showed very high SWR. I am
using a Carolina 40 Windom antenna by Radio works.
I re-arranged the configuration of the watt meter by connecting the RF out
from the K2100 to the TR connector on the external watt meter. Then the ANT
connector on the external watt meter goes to RF in on the KAT100. Then I
connected the antenna to the ANT1 on the KAT100. I then went through the
bands. The KAT100 re-adjusted the settings on all bands. Now the external
watt meter shows matched power out readings compared to the K2100 display.
The SWR is low on all the bands according to the external watt meter, KAT100
and K2100. Is this the best way to have an external watt meter connected?
================================================
Dave Gingrich, K9DC - Indianapolis, Indiana USA
K2 #2211, K1 #931, QRP-L #2376, ARS #1109,
FPQRP #389, IRLP 4730/5730, k9dc.ampr.org
================================================
Stuart Rohre
2003-01-30 18:29:04 UTC
Permalink
Most external watt meters are designed to go between a rig and a tuner, as
they are ONLY accurate in a 50 ohm matched line. Any one used downstream
toward the antenna from the tuner, in the transmission line that has SWR is
suspect of not reading under its expected impedance requirements to read
accurate SWR. On a tuned line, after the tuner, the line plus antenna is
being tuned as a system and will have swr on it, unless the line
accidentally matches the antenna impedance exactly on some band(s).
That only matters in that coax has higher losses when operated with SWR
higher than 1:1 matched condition; as in a doublet used on multi bands.

When you tune a transmatch, the 50 ohms is made to appear at the transceiver
side, and it may be something vastly different on the transmission line/
antenna side.
72,
Stuart K5KVH
k***@juno.com
2003-01-30 18:22:02 UTC
Permalink
Glenn, WA7SPY wrote:

"I have a question as to what is the best way to use an external watt
meter?"
==========
Directly at the output of the K2/100.

The term "antenna tuner" is really a misnomer. By no means does it
increase the efficiency of an antenna.

In your case, the "antenna tuner" does not tune the antenna. It merely
tunes the load the transmitter is fed into (which is the Carolina windom
feedline in your case) so that it looks like it is 50 + j0 ohms, and the
transmitter "thinks" it is looking into a 1:1 SWR.

Therefore, with your wattmeter connected between the KAT100 and the
Carolina windom feedline, the actual SWR on the feedline will be
indicated (which might be high).

With the wattmeter connected between the K2/100 and the KAT100, the
indicated SWR will be what the output of the K2/100 is looking into
(which will be low).

73, de Earl, K6SE
Tom Hammond
2003-01-30 23:20:59 UTC
Permalink
Post by Glenn Maclean
I have a question as to what is the best way to use an external watt meter?
I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to connector
labeled TR on the external watt meter and then the antenna connected to
the connector labeled ANT on the external watt meter. I was getting a good
match according to the K2100 display and the KAT100 LED's. The external watt
meter however was showing high SWR on some bands especially 30 meters. On 40
meters and 20 meters the external watt meter, KAT100 and K2100 SWR displays
all agree. On other bands the external watt meter showed very high SWR. I am
using a Carolina 40 Windom antenna by Radio works.
The KAT100 _ONLY_ changes the impedance of the load it's being presented
between its ANT1 jack and the K2!!! Even though the ATU has done its job,
by providing an acceptable SWR to the K2, it has NOT changed the load
impedance of the antenna or its feedline.

As a result, the external wattmeter will always indicate the REAL SWR being
presented to the KAT100, and the KAT100 will indicate the 'TUNED' SWR being
presented to the K2.
Post by Glenn Maclean
I re-arranged the configuration of the watt meter by connecting the RF out
from the K2100 to the TR connector on the external watt meter. Then the ANT
connector on the external watt meter goes to RF in on the KAT100. Then I
connected the antenna to the ANT1 on the KAT100. I then went through the
bands. The KAT100 re-adjusted the settings on all bands. Now the external
watt meter shows matched power out readings compared to the K2100 display.
The SWR is low on all the bands according to the external watt meter, KAT100
and K2100. Is this the best way to have an external watt meter connected?
It all depends upon what it is you want the DIAWA meter to indicate.

If you want it to duplicate the reading of the KAT100, then you have it
configured properly right now.

However, if you want to use the DIAWA to indicate actual SWR _ON_ the
feedline going to the antenna, then you should put it on the OUTPUT of the
KAT100, so it 'sees' what the antenna and feedline are doing.

73,

Tom N0SS
Glenn Maclean
2003-01-31 01:04:01 UTC
Permalink
Thanks to all who replied to my watt meter question. I had numerous answers.
Thank you to all. If my understanding is correct this is what is going on.
The KAT100 automatic tuner is doing exactly what it is suppose to do. It is
making the KPA100 finals (tank circuit) happy with a 50 ohm impedance match
keeping the current and voltage in a satisfactory range. However this does
not mean the antenna is performing very well on some bands. I was able to
see this when the watt meter was connected after the tuner and showed a very
high SWR especially on 30 meters and some of the other bands. When the watt
meter is showing a low SWR the antenna is resonant on those bands and
performing well.. On the bands with a high SWR the tuner is absorbing a lot
of power which means the EFR (effective radiated power) at the antenna is
very poor.

Thanks again to all who replied,
Glenn WA7SPY

Orginal Message -----
From: "Tom Hammond" <***@earthlink.net>
To: "Glenn Maclean" <***@attbi.com>; <***@mailman.qth.net>
Sent: Thursday, January 30, 2003 2:08 PM
Subject: Re: [Elecraft] KAT100 and external watt meter question
Post by Tom Hammond
Post by Glenn Maclean
I have a question as to what is the best way to use an external watt meter?
I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to connector
labeled TR on the external watt meter and then the antenna connected to
the connector labeled ANT on the external watt meter. I was getting a good
match according to the K2100 display and the KAT100 LED's. The external watt
meter however was showing high SWR on some bands especially 30 meters. On 40
meters and 20 meters the external watt meter, KAT100 and K2100 SWR displays
all agree. On other bands the external watt meter showed very high SWR. I am
using a Carolina 40 Windom antenna by Radio works.
The KAT100 _ONLY_ changes the impedance of the load it's being presented
between its ANT1 jack and the K2!!! Even though the ATU has done its job,
by providing an acceptable SWR to the K2, it has NOT changed the load
impedance of the antenna or its feedline.
As a result, the external wattmeter will always indicate the REAL SWR being
presented to the KAT100, and the KAT100 will indicate the 'TUNED' SWR being
presented to the K2.
Post by Glenn Maclean
I re-arranged the configuration of the watt meter by connecting the RF out
from the K2100 to the TR connector on the external watt meter. Then the ANT
connector on the external watt meter goes to RF in on the KAT100. Then I
connected the antenna to the ANT1 on the KAT100. I then went through the
bands. The KAT100 re-adjusted the settings on all bands. Now the external
watt meter shows matched power out readings compared to the K2100 display.
The SWR is low on all the bands according to the external watt meter, KAT100
and K2100. Is this the best way to have an external watt meter connected?
It all depends upon what it is you want the DIAWA meter to indicate.
If you want it to duplicate the reading of the KAT100, then you have it
configured properly right now.
However, if you want to use the DIAWA to indicate actual SWR _ON_ the
feedline going to the antenna, then you should put it on the OUTPUT of the
KAT100, so it 'sees' what the antenna and feedline are doing.
73,
Tom N0SS
Stuart Rohre
2003-01-31 01:25:59 UTC
Permalink
ACTUALLY, the antenna performs the same whether or not you have SWR equal to
1:1!

The only difference when not 1:1 impedance relation to the feedline, is that
there will be higher line losses. Pattern, radiation efficiency etc. are
not a function of SWR, but of antenna design, height, construction material
etc.

The antenna does not care about what line is connected to it, it is going
"to do its thing" with whatever power reaches the antenna after
rereflections.
73, Stuart K5KVH
George, W5YR
2003-01-31 06:50:01 UTC
Permalink
As Roy Lewallen W7EL of EZNEC "fame" reminds us, power must be
conserved. Power that leaves the transmitter must eventually end up at
the antenna, less what might be lost along the way in a tuner or in
line loss. And, given sensible tuner design and adjustment and
low-loss line suited to high SWR conditions, most of the power that
leaves the transmitter will leave the antenna as radiation, despite a
high SWR on the line.

To put some numbers into the discussion, it turns out that 100 ft of
600-ohm open-wire line terminated in an antenna impedance of 94+j500
ohms (a significantly non-resonant antenna!) on 20 meters will operate
at an SWR of 10:1 and show a total power loss of only 0.38 dB and will
deliver nearly 92% of the applied power. Even at an SWR of 20:1 (load
= 43+j500 ohms), the line loss is only 0.78 dB for an efficiency of
nearly 84%.

Try the same thing with RG-213, though, and although you will see
about the same SWR (about 11:1 for the same load Z), the power loss
soars to 10.3 dB and the efficiency drops to only 9.33%. Here a high
SWR is something to be concerned about because of the excessive line
loss it produces in a line unsuited to the application.

The goal of good engineering is to match methods and materials to the
job to be done, and the open-wire line is clearly the better choice.
Note that although the actual SWR is about the same in both cases -
around 11:1 or so - with a low-loss line, the system operates at
quite acceptable efficiency.

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 IC-765 #2349 IC-756 PRO #2121 IC-756 PRO2 #3235

----- Original Message -----
From: "Stuart Rohre" <***@arlut.utexas.edu>
To: "Glenn Maclean" <***@attbi.com>; <***@mailman.qth.net>;
"Tom Hammond" <***@earthlink.net>
Sent: Thursday, January 30, 2003 6:22 PM
Subject: Re: [Elecraft] KAT100 and external watt meter question
Post by Stuart Rohre
ACTUALLY, the antenna performs the same whether or not you have SWR equal to
1:1!
The only difference when not 1:1 impedance relation to the feedline, is that
there will be higher line losses. Pattern, radiation efficiency etc. are
not a function of SWR, but of antenna design, height, construction material
etc.
The antenna does not care about what line is connected to it, it is going
"to do its thing" with whatever power reaches the antenna after
rereflections.
73, Stuart K5KVH
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John Buck
2003-01-31 01:55:01 UTC
Permalink
Glenn,

There is much mythology in the summary quoted below.

A high SWR at the feed line is not an indication of poor performance as
long as the antenna tuner provides a good match to the transmitter. A
high swr merely indicates the the antenna/feed line is showing an
impedance other that 50 ohms. The reflected power is not lost unless
the transmission line losses are high. The power is mostly reflected
back toward the antenna and does not heat the tuner. Many excellent
antennas operate at design impedance's of 400, 600, or higher, ohm
impedance's.

The conclusion that High SWR indicates a high loss in the tuner is
wrong. If the impedance is very low the resulting high current may cause
I squared R heating. Otherwise the losses in good (and properly tuned)
tuners are quite low.

Like wise, the concept that low SWR at the end of the feed line
indicates a good antenna can be wrong. An end fed half wave has
extremely high impedance. When properly matched it can be extremely
efficient. By the way, both a dummy load and a very long piece of coax
may indicate a 50 ohm "match" even if the antenna is broken, due to
losses in the feed line.

I do agree that that if an antenna is designed for a 50 ohm impedance
and your swr changes from 1.5 to 1 to something greater than 2 or 3 to 1
then something is broken. The Carolina Windom is not 50 ohms on all
bands. But when properly matched with a tuner, it can perform well.

The concept that an antenna must be resonant is also a bit of folklore.
Various non resonant lengths of wire work nearly as well as a resonant
dipole when properly fed with a low loss feed line and tuner. They have
the advantage of working well on several bands without lossy traps and
extra wire. Dipoles do not work well on the second harmonic.

By the way, the characteristic impedance of a dipole with good height is
70 or 100 ohms. With a good low loss feed line the SWR at the shack
might be about 1.5 to 1. A higher loss system might show close to 1 to
1. So if you have this situation, use it and enjoy. Obsession about
1.01 to 1 SWR is of no use. If your transmitter is happy running full
power out into a 2 to 1 SWR, relax and enjoy. Some rigs start folding
back at about that level so you want to match well enough to avoid
foldback. It has been widely assumed by too many people that anything
other that 1.1 to 1 is unacceptable. 1.5 to 1 might be indicating an
optimal low loss setup!

Aloha,
John KH7T
Post by Glenn Maclean
Thanks to all who replied to my watt meter question. I had numerous answers.
Thank you to all. If my understanding is correct this is what is going on.
The KAT100 automatic tuner is doing exactly what it is suppose to do. It is
making the KPA100 finals (tank circuit) happy with a 50 ohm impedance match
keeping the current and voltage in a satisfactory range. However this does
not mean the antenna is performing very well on some bands. I was able to
see this when the watt meter was connected after the tuner and showed a very
high SWR especially on 30 meters and some of the other bands. When the watt
meter is showing a low SWR the antenna is resonant on those bands and
performing well.. On the bands with a high SWR the tuner is absorbing a lot
of power which means the EFR (effective radiated power) at the antenna is
very poor.
Thanks again to all who replied,
Glenn WA7SPY
Don Wilhelm
2003-01-31 05:04:01 UTC
Permalink
----- Original Message -----
... Dipoles do not work well on the second harmonic.
...
Folks,
It is fair to say that a dipole (fed with coax) does not work (match) well
on the second harmonic, but it is quite true that the antenna itself is a
very efficient radiator - in fact a full wavelength antenna is also known as
'two half waves in phase' and can show up to 3dB of gain in its favorable
direction (single bi-directional lobes broadside to the antenna).

A full wavelength antenna fed in the center does have a very high feedpoint
impedance, but a good quality open wire line or ladderline will handle it
with ease - one can use a tuner that can handle the high impedance or use a
feedline length of something close to an odd multiple of a quarter
wavelength to transform the feedpoint impedance to a lower value where your
tuner can easily match it (don't shoot for an extremely low impedance though
because resistive losses in the tuner often are much higher due to the
increased current when feeding an extremely low impedance - like less than
20 or 25 ohms).

73,
Don W3FPR
John Buck
2003-01-31 01:15:04 UTC
Permalink
Tom, I believe a clarification is in order.
As you correctly state, the KAT-100 does not change the impedance at the
output of the KAT 100. Since the impedance at that point is not 50 ohms
unless a dummy load or matched antenna are used, and most SWR meters and
Power meters including the DAIWA read correctly only if at a 50 ohm
node, the meter will not indicate SWR or Power accurately unless the
load is 50 ohms. I know that the FWD and Rev power reading will not be
accurate. Is it possible that the SWR indicated by the ratio is correct
even if the load impedance is way off from 50 ohms? Certainly the
forward power and is not accurate.

Glen, your observations are probably correct. You will get a good match
on those frequencies where your antenna is close to 50 ohms and you will
get false readings on those bands that are not 50 ohms. If you put the
watt meter between the KPA-100 and the KAT-100 you will be operating at
a 50 ohm node and seeing accurate results. Placing a good 50 ohm meter
on the unmatched node is not usually a good idea. The voltages can get
very high on some antennas.

Aloha,
John KH7T
Post by Tom Hammond
Post by Glenn Maclean
I have a question as to what is the best way to use an external watt meter?
I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to connector
labeled TR on the external watt meter and then the antenna connected to
the connector labeled ANT on the external watt meter. I was getting a
good match according to the K2100 display and the KAT100 LED's. The
external watt meter however was showing high SWR on some bands especially 30 meters.
On 40 meters and 20 meters the external watt meter, KAT100 and K2100 SWR
displays all agree. On other bands the external watt meter showed very high
SWR. I am
using a Carolina 40 Windom antenna by Radio works.
The KAT100 _ONLY_ changes the impedance of the load it's being presented
between its ANT1 jack and the K2!!! Even though the ATU has done its
job, by providing an acceptable SWR to the K2, it has NOT changed the
load impedance of the antenna or its feedline.
As a result, the external wattmeter will always indicate the REAL SWR
being presented to the KAT100, and the KAT100 will indicate the 'TUNED'
SWR being presented to the K2.
Post by Glenn Maclean
I re-arranged the configuration of the watt meter by connecting the RF out
from the K2100 to the TR connector on the external watt meter. Then the ANT
connector on the external watt meter goes to RF in on the KAT100. Then I
connected the antenna to the ANT1 on the KAT100. I then went through the
bands. The KAT100 re-adjusted the settings on all bands. Now the external
watt meter shows matched power out readings compared to the K2100 display.
The SWR is low on all the bands according to the external watt meter, KAT100
and K2100. Is this the best way to have an external watt meter connected?
It all depends upon what it is you want the DIAWA meter to indicate.
If you want it to duplicate the reading of the KAT100, then you have it
configured properly right now.
However, if you want to use the DIAWA to indicate actual SWR _ON_ the
feedline going to the antenna, then you should put it on the OUTPUT of
the KAT100, so it 'sees' what the antenna and feedline are doing.
73,
Tom N0SS
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Cormac Thompson
2003-01-31 03:39:00 UTC
Permalink
Salutations:

Related to this thread is an observation made today when I installed a new
KAT1 board in my new K1-4.

After adjusting it with a dummy load per the instructions, I proceeded to
hook it up to the G5RV with a Diamond SWR bridge in line (about 3 feet) from
the K1 output.

The tuner did not want to tune the antenna on any band properly and the
output power was lower than normal while the SWR on the external wattmeter
read way high.
After playing with this for a half hour, I called Scott at Elecraft and
expressed my dismay.

Once he found out about the external wattmeter in line the problem was
solved. You simply cannot get proper operation from the tuner with that
thing in there.
As soon as I removed it, the tuner brought the SWR down to normal, usually
1.0 and even 1.5 on 30 meters.
Everything back to normal.

Previously I had been using a high power manual tuner in a traditional T
type with roller inductor. I could never tune the G5RV on 30 meters before.
And I noticed that signals on 40 and 20 meters were noticeably stronger than
they had been during the previous 2 weeks of operation and it wasn't band
conditions. I had to readjust the high end S meter reading!

The point worth remembering is: whenever you adjust a tuner for minimum SWR
it occurs wherever the bridge is located. Insert a bridge anywhere else in
the line and you'll find all kinds of readings depending on the location!

Thanks to Scott for his fine technical support during this project. I am
impressed.

Cormac "Mac", W7JHS
K1-4 #1476
----- Original Message -----
From: "John Buck" <***@arrl.net>
To: "Tom Hammond" <***@earthlink.net>
Cc: "Glenn Maclean" <***@attbi.com>; <***@mailman.qth.net>
Sent: Thursday, January 30, 2003 4:11 PM
Subject: Re: [Elecraft] KAT100 and external watt meter question
Tom Hammond
2003-01-31 06:31:01 UTC
Permalink
Post by Cormac Thompson
After adjusting it with a dummy load per the instructions, I proceeded to
hook it up to the G5RV with a Diamond SWR bridge in line (about 3 feet) from
the K1 output.
The tuner did not want to tune the antenna on any band properly and the
output power was lower than normal while the SWR on the external wattmeter
read way high.
After playing with this for a half hour, I called Scott at Elecraft and
expressed my dismay.
Once he found out about the external wattmeter in line the problem was
solved. You simply cannot get proper operation from the tuner with that
thing in there.
As soon as I removed it, the tuner brought the SWR down to normal, usually
1.0 and even 1.5 on 30 meters. Everything back to normal.
Though you noticed the difference, I somewhat doubt that it was due to the
external bridge, but rather the fact that you changed your feedline length
by 3' of coax. Try putting the coax BACK in the line, but use a
double-female adapter in place of the external bridge. Chances are your
tuning problem will return.

I say this because I've run external SWR bridges in-line for decades with
no problems whatsoever... still do to this day. BUT I have, in the past,
found that if there's an appreciable SWR on the feedline coming into the
shack, the length of the feedline CAN change to point at which you're
looking' at the load, and it can sometimes cause tuning problems for
transmatches. Changing the length of the feedline changes the point (along
the line) where you look at the load and can make tuning easier.

Of course, adding/removing line length does NOT change the SWR, on the
line, just the point at which you (or the ATU) look at it.

73,

Tom N0SS
Dave Gingrich K9DC
2003-01-31 05:14:01 UTC
Permalink
On Thursday, Jan 30, 2003, at 19:00 America/Indianapolis, Glenn Maclean
Post by Glenn Maclean
Thanks to all who replied to my watt meter question. I had numerous
answers.
Thank you to all. If my understanding is correct this is what is going
on.
The KAT100 automatic tuner is doing exactly what it is suppose to do.
It is
making the KPA100 finals (tank circuit) happy with a 50 ohm impedance
match
keeping the current and voltage in a satisfactory range. However this
does
not mean the antenna is performing very well on some bands.
The ability of an antenna to "perform very well" has very little to do
with SWR on the feedline... But that is an entirely different
question. HI.

===========================
Dave Gingrich, K9DC
Indianapolis, Indiana USA
===========================
Bozidar Benc
2003-02-01 00:02:54 UTC
Permalink
A (dumb) question:

How can one calculate the actual loss, given the SWR, cable length and cable
loss/ft at working frequency?

73, Bole - 9A3RR
-----Original Message-----
Sent: Friday, January 31, 2003 6:47 AM
Subject: Re: [Elecraft] KAT100 and external watt meter question
[snip]
Try the same thing with RG-213, though, and although you will see
about the same SWR (about 11:1 for the same load Z), the power loss
soars to 10.3 dB and the efficiency drops to only 9.33%. Here a high
SWR is something to be concerned about because of the excessive line
loss it produces in a line unsuited to the application.
Stuart Rohre
2003-02-01 00:08:00 UTC
Permalink
There is a loss table in ARRL Handbook for typical coax losses under various
SWR conditions. Also in many Antenna books. Actually a good question, and
there are likely such charts on the web. Google.com search keywords:
"Coax SWR losses" or similar combinations.
72,
Stuart K5KVH
Bozidar Benc
2003-02-01 00:36:00 UTC
Permalink
Yes, coax losses are easy to find
(http://www.radiobooks.com/products/techinfo/coaxloss.htm for example), but
I guess that they are for the case when SWR is 1:1.

What I would like to know is how George calculated the 10.3 dB loss in his
example.

Bole
-----Original Message-----
Sent: Saturday, February 01, 2003 12:05 AM
To: Bozidar Benc; elecraft
Subject: Re: [Elecraft] KAT100 and external watt meter question
There is a loss table in ARRL Handbook for typical coax losses
under various
SWR conditions. Also in many Antenna books. Actually a good
question, and
"Coax SWR losses" or similar combinations.
72,
Stuart K5KVH
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George, W5YR
2003-02-01 00:50:01 UTC
Permalink
With TLDetails, I found a combination of R and X for the load that
produced a 10.3 dB loss in the RG-213 coax for a length of 100 feet on
20 meters, and produced an SWR of about 11:1. I didn't have to
calculate it - took the easy way out! <:}

IF you want to do it manually, get a Smith chart and start fishing for
values of load that result in the SWR that will give 10.2 dB loss in
100 ft of RG-213 on 20 meters. The loss data comes from the tables in
the Handbook as Stuart suggested. But recall that there is a
semi-infinite set of combinations of R and X that will fit on that SWR
circle on the chart.

Hope this answers your questions. BTW, there are many good
transmission line analysis programs available these days. I just
happen to prefer TLDetails . . .

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 IC-765 #2349 IC-756 PRO #2121 IC-756 PRO2 #3235

----- Original Message -----
From: "Bozidar Benc" <***@benc.hr>
To: "Stuart Rohre" <***@arlut.utexas.edu>; "elecraft"
<***@mailman.qth.net>
Sent: Friday, January 31, 2003 5:32 PM
Subject: RE: [Elecraft] KAT100 and external watt meter question
Post by Bozidar Benc
Yes, coax losses are easy to find
(http://www.radiobooks.com/products/techinfo/coaxloss.htm for
example), but
Post by Bozidar Benc
I guess that they are for the case when SWR is 1:1.
What I would like to know is how George calculated the 10.3 dB loss in his
example.
Bole
-----Original Message-----
Sent: Saturday, February 01, 2003 12:05 AM
To: Bozidar Benc; elecraft
Subject: Re: [Elecraft] KAT100 and external watt meter question
There is a loss table in ARRL Handbook for typical coax losses
under various
SWR conditions. Also in many Antenna books. Actually a good
question, and
there are likely such charts on the web. Google.com search
"Coax SWR losses" or similar combinations.
72,
Stuart K5KVH
Stuart Rohre
2003-02-01 01:07:00 UTC
Permalink
No, some of the Handbooks have the losses for various values of SWR and the
kind of loss table you found.

The loss table you found is for cable loss PER 100 FT.
That is intrinsic loss in coax due to its vast amounts of plastic dielectric
that you heat up, before you ever get to issues of SWR losses.

(That is a useful table at www.radiobooks for cable per foot losses.)
73, Stuart K5KVH
George points out the SWR calculation programs are readily available, and I
think Hamcalc may include one. (The Murphy CDs of ham software).
Bozidar Benc
2003-02-01 01:31:00 UTC
Permalink
Thanks a lot for the advice. TLDetails is a great little prog.

73, Bole
-----Original Message-----
Sent: Saturday, February 01, 2003 12:47 AM
To: Bozidar Benc; Stuart Rohre; elecraft
Subject: Re: [Elecraft] KAT100 and external watt meter question
With TLDetails, I found a combination of R and X for the load that
produced a 10.3 dB loss in the RG-213 coax for a length of 100 feet on
20 meters, and produced an SWR of about 11:1. I didn't have to
calculate it - took the easy way out! <:}
IF you want to do it manually, get a Smith chart and start fishing for
values of load that result in the SWR that will give 10.2 dB loss in
100 ft of RG-213 on 20 meters. The loss data comes from the tables in
the Handbook as Stuart suggested. But recall that there is a
semi-infinite set of combinations of R and X that will fit on that SWR
circle on the chart.
Hope this answers your questions. BTW, there are many good
transmission line analysis programs available these days. I just
happen to prefer TLDetails . . .
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 IC-765 #2349 IC-756 PRO #2121 IC-756 PRO2 #3235
----- Original Message -----
Sent: Friday, January 31, 2003 5:32 PM
Subject: RE: [Elecraft] KAT100 and external watt meter question
Post by Bozidar Benc
Yes, coax losses are easy to find
(http://www.radiobooks.com/products/techinfo/coaxloss.htm for
example), but
Post by Bozidar Benc
I guess that they are for the case when SWR is 1:1.
What I would like to know is how George calculated the 10.3 dB loss
in his
Post by Bozidar Benc
example.
Bole
-----Original Message-----
Sent: Saturday, February 01, 2003 12:05 AM
To: Bozidar Benc; elecraft
Subject: Re: [Elecraft] KAT100 and external watt meter question
There is a loss table in ARRL Handbook for typical coax losses
under various
SWR conditions. Also in many Antenna books. Actually a good
question, and
there are likely such charts on the web. Google.com search
"Coax SWR losses" or similar combinations.
72,
Stuart K5KVH
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