[Elecraft] Attic Antenna

[Larry]

I live in a restricted community and am thinking about putting a 20
meter dipole in the attic. I know most of the issues with doing this but
I don't know the effect the roofing material will have on my signal. The
roof is 1/2 in thick cement tiles. Has anyone had experience with this
setup?

Thanks,

Larry, KB5DXY
K1 #2269

[Ron D'Eau Claire]

I live in a restricted community and am thinking about putting a 20
meter dipole in the attic. I know most of the issues with doing this but
I don't know the effect the roofing material will have on my signal. The
roof is 1/2 in thick cement tiles. Has anyone had experience with this
setup?

Thanks,

Larry, KB5DXY
K1 #2269

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

Yep! Not all tiles are equal, so you may be better off. I moved several
times about 15 years ago, always living in an apartment. I managed to get a
top (second) floor apartment in each case and installed a doublet in the
attic in each case. It was hung just under the rafters.

In one apartment I noticed that I didn't get out very well, compared to my
previous QTH, but my antenna arrangement was very similar! On air testing is
just about useless to determine how well an antenna is working so I didn't
panic over it. But, over several months a suspicion grew.

One day I noticed walk near my building a piece of roofing tile that had
apparently dropped there while some repairs were being done. Curious, I took
it indoors. It was a hot summer day and the tile piece was quite dry. I put
it in my microwave oven (with a glass of water to avoid running it 'empty')
let it cook for a minute or two.

The roof tile was very hot! That's a sure sign it's pretty opaque to RF. Of
course, it's probably more opaque at microwave frequencies than at HF, but
it's still going to be lossy. If you can get a piece of tile, do the test
for yourself. You may be a lot better off than I was.

I did a little research and found that those tile mixes often have a lot of
stuff not normally found in concrete and that the formulas vary
substantially from one supplier to another. That's about all I could dig up
on the subject. Let me say that I made a LOT of contacts from under those
tiles, using QRP on 40 and 20 meters, including substantial DX. That's the
problem with on-air testing. A punk poor antenna can sound *great* when the
band conditions are right. So if that's what you have to do to get on the
air, go for it.

Ron AC7AC

[Rick Dettinger]

Post by Larry
I live in a restricted community and am thinking about putting a 20
meter dipole in the attic. I know most of the issues with doing this but
I don't know the effect the roofing material will have on my signal. The
roof is 1/2 in thick cement tiles. Has anyone had experience with this
setup?
Thanks,
Larry, KB5DXY
K1 #2269

=========================================
The attenuation of any materal is a function of its thickness, measured in
wavelengths, as well as its electrical properties. This means that for a
given roof material, you will have less signal attenuation at 160 M then at
10 M. This should be true for trees, rain or snow also. This is why the US
Navy uses extreme low frequencies to communicate with subs under water.
Like in the audio range, except its still radio.
I tried a 20 M. dipole in my wood framed attic before I hade an antenna
tuner. The SWR was way high, like 4:1. I think this was due to the close
proximity of electrical wires. The antenna would probably have worked fine
with a tuner.
Rick Dettinger
K7MW

[Larry]

Thanks for all of the great feedback. I am going to research some of the
antenna suggestions that I have received. I feel a lot more confident in
trying an antenna in the attic now.

I am currently building my K1. I have finished the receiver and am
starting the transmitter section. I will also be adding a KAT1. I will
report back with results when I get the whole thing working.

Larry, KB5DXY
K1 #2269 (in progress)

[Craig D. Smith]

Larry .



I have experience with a similar situation. I'm also in a HOA restricted
development. I put up an antenna in the attic here when I first started
operating from this QTH. Basically a 17 meter doublet with 300 ohm
ladderline feeder that I can load on all bands from 10 to 40 with the
internal tuner in my K2 and an Elecraft balun. My shingles are the more
normal asphalt type, but the exterior sheathing of the house has an aluminum
coating on one side which no doubt attenuates the RF some. And of course
the antenna picks up more powerline noise and noise from household
electronics than would an outside antenna.



I've made a few hundred contacts on it on 40, 30, 20 and 17 using the 10
watts CW from my K2. Haven't really tried on 15, 12 and 10 due to the
current sunspot situation. So it will work.



That said, this year I got a Buddipole and set it up when I operate on a
temporary basis on the patio. I most normally use it in a vertical
arrangement with a single counterpoise wire and an extra length shock-cord
whip assembly. This will run circles around the attic dipole, especially
for DX. At least 2 S units better. And it is fairly low profile, so that
you might be able to get away with it as far as your neighbors are
concerned. Within 10 minutes yesterday I worked the XF4DL DXpedition on 20
and 17 with the Buddipole and 10W from Colorado. The day before I worked
them on 40. The attic dipole has been effective mostly for stateside
contacts.



Another antenna I have that could be a possibility for you is a set of
base-fed verticals running up one side of the house. You can feed them all
with one feedline. The proximity of the house and the other radiators will
detune them, but a couple of hours with an antenna analyzer will sort
everything out. I have the 40 and 80 meter elements running over the
rooftop in an inverted L arrangement. By inserting some base loading, I can
use the 80 meter element on 160. All this is VERY stealth - use the AWG 26
stealth black insulated copperweld wire and paint it to match your house.
Lay a few radials out on the ground and around your foundation. The
performance of this arrangement here is about midway between the attic
dipole and the outside Buddipole Vertical.



The key is to be open-minded and experiment - you will find something that
works. The attic dipole is a good place to begin and will always be a good
secondary antenna even if you find something you like better later on.





73

. Craig AC0DS

[Fred (FL)]

Hi -

I notice Diamond Antennas - now offers a BB7V and
BB6W VERTICAL NO-COUNTERPOISE HF ANTENNA - for the ham
bands. They look to be built very well. The
BB6W version, offers a HORIZONTAL top section, up
above the antenna's loading coil. Whole thing mounts
on a single vertical pole, etc.

The BB7V is sold by Universal Radio Inc. in Ohio. I
think the BB6W is not yet available at any U.S.
ham stores. But may be wrong on that.

I saw an article where the Australian hams were using
the BB7V with success. I'm sure a tuner is required.

Fred
N3CSY
.....stealth, association restricted too ....

__________________________________________________
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[n2ey at aol.com ()]

-----Original Message-----
Diamond Antennas - now offers a BB7V and
BB6W VERTICAL NO-COUNTERPOISE HF ANTENNA - for the ham
bands. They look to be built very well.

---


I would want a lot more info before spending any money.

The BB7V is priced at US$400. It's a 22 foot vertical aluminum radiator
with a nice mast clamp (mast not included) and a cylindrical feedpoint
device.

The big question is: What's in the feedpoint device?

None of the literature gives any detail on how the feedpoint device
converts the complex impedance at the bottom of the 22 foot vertical
radiator into 50 ohms. SWR of 2 or less from 2 to 30 MHz is claimed.
The feedpoint device does not have any external controls or indications.

The radiator and mast clamp assembly can't be worth more than $100
retail. So what is in the feedpoint device that is worth $300?

The name "Maxx-Comm" comes to mind.....

73 de Jim, N2EY
________________________________________________________________________
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[Vic K2VCO]

Post by n2ey at aol.com ()
I would want a lot more info before spending any money.
The BB7V is priced at US$400. It's a 22 foot vertical aluminum radiator
with a nice mast clamp (mast not included) and a cylindrical feedpoint
device.
The big question is: What's in the feedpoint device?

Here's some more information (but no mention of what's in the magic
cylinder): <http://www.hamradio.co.uk/pdf/Diamond/BB7V.pdf>

However, it is possible to see that the radiator is a continuous
conductor. Therefore, the counterpoise function must be provided by the
mast, coax shield, or lossy ground (depending on mounting). This means
the antenna's performance would be highly dependent on mounting, and it
would be prone to RFI and RF-in-the-shack issues.

The antenna supposedly works from 3-30 MHz with SWR less than 2:1. The
SWR curve shown is suspiciously similar to that of a resistively loaded
antenna. Such antennas can be useful in certain circumstances (B&W
makes several versions), but the efficiency can be quite low on
frequencies where the impedance of the radiating part is high or
reactive. The B&W antennas are well designed and relatively large; even
so, the efficiency is significantly below that of a dipole.

A 22-foot vertical without top loading will be inefficient on 7 MHz (it
will be a dummy load on 3.5), especially without a decent counterpoise.

Even if one only has room for a 22-foot vertical there are lots of
better choices.

I agree with Jim. Put up a dipole and spend the leftover $395 on beer.

[Bob Nielsen]

It reminds me of the verticals Gotham made in the 1950s.

Bob, N7XY

[n2ey at aol.com ()]

-----Original Message-----
From: ***@oz.net

It reminds me of the verticals Gotham made in the 1950s.?
?
----

But it's very different.

The Gotham verticals were just 22 feet of tubing, some mounting straps,
and a big custom-made coil of B& W miniductor. The only difference
between the various models was how big a coil they sent.

You supplied the feedline, mounting, some hardware, a ground or
counterpoise, and a weatherproof cover for the coil.

The way the Gotham verticals worked was that you connected the coil
between the bottom of the 22 foot radiator and ground/counterpoise.
Then you connected the coax braid to ground.

You also needed to tap the coax center conductor onto the coil, and to
short out turns at the top of the coil.

The trick was that with the right number of turns shorted out at the
top of the coil, and the center conductor tapped on at the right spot,
you'd get a low SWR on the frequency of your choice. Of course if you
QSYd, you had to go change the taps and shorting jumper. Since the coil
was at the base of the antenna, that could be convenient - maybe.

Depending on how good the ground connection was, and what band you were
using, performance could range from great to awful. 22 feet is about
5/8 wave on 10 meters, too.

The BB7W doesn't work like that. There's some sort of magic,
nonadjustable network inside the feedpoint device. I suspect it has a
near-unity power factor.....


73 de Jim, N2EY




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Check out the new AOL. Most comprehensive set of free safety and
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[Stuart Rohre]

The Diamond bottom tube may, (and likely) contains a broad band ferrite
cable choke. Or there may be a combination trap/ loading coil such as used
on some tri band beams for multibands.

Stuart
K5KVH

[Vic K2VCO]

Post by Stuart Rohre
The Diamond bottom tube may, (and likely) contains a broad band ferrite
cable choke. Or there may be a combination trap/ loading coil such as used
on some tri band beams for multibands.

No way that a choke would produce the SWR curve shown in their spec
sheet. Whatever else is in there, there's also a resistor.

[Sandy W5TVW]

WARNING!!!!!!!!!
This same scheme (scam?) happened quite a few years ago. Don't remember the name
of the "device", but is was a "black box" type "proprietary" antenna coupler.
The price was rather high ($300-400) and it was guaranteed "flat SWR"
between 3-30 Mhz.
SO-239 input and two standoff insulators with wing nuts (output). Was said
to match a random wire or a balanced line dipole! Someone finally
"x-rayed" one and it turned out to be a dummy load actually. It was
enclosed in a cast aluminum "Bud box" and potted with some sort
of opaque epoxy if you took the lid off!
They didn't last too long, but long enough for the manufacturer to
make a bundle! It was not guaranteed to radiate with high efficiency
but was guaranteed to have an input VSWR no greater than 2:1!
BEWARE of ANY "MAGIC DEVICE" that makes these claims.
More than likely it is a large pile of bovine fecal matter that they
are feeding you!

No, I didn't buy one, but in some "unusual installations" it was
tried on some commercial marine limited coast station installations.
The results were very mediocre no matter what 'antenna' was tried.
Low SWR....BUT! Not much radiation!

73,
Sandy W5TVW
----- Original Message -----
From: "Vic K2VCO" <***@rakefet.com>
To: <***@aol.com>
Cc: <***@mailman.qth.net>
Sent: Friday, October 27, 2006 12:01 PM
Subject: Re: [Elecraft] Attic Antenna


| ***@aol.com wrote:
|
| > I would want a lot more info before spending any money.
| >
| > The BB7V is priced at US$400. It's a 22 foot vertical aluminum radiator
| > with a nice mast clamp (mast not included) and a cylindrical feedpoint
| > device.
| >
| > The big question is: What's in the feedpoint device?
|
| Here's some more information (but no mention of what's in the magic
| cylinder): <http://www.hamradio.co.uk/pdf/Diamond/BB7V.pdf>
|
| However, it is possible to see that the radiator is a continuous
| conductor. Therefore, the counterpoise function must be provided by the
| mast, coax shield, or lossy ground (depending on mounting). This means
| the antenna's performance would be highly dependent on mounting, and it
| would be prone to RFI and RF-in-the-shack issues.
|
| The antenna supposedly works from 3-30 MHz with SWR less than 2:1. The
| SWR curve shown is suspiciously similar to that of a resistively loaded
| antenna. Such antennas can be useful in certain circumstances (B&W
| makes several versions), but the efficiency can be quite low on
| frequencies where the impedance of the radiating part is high or
| reactive. The B&W antennas are well designed and relatively large; even
| so, the efficiency is significantly below that of a dipole.
|
| A 22-foot vertical without top loading will be inefficient on 7 MHz (it
| will be a dummy load on 3.5), especially without a decent counterpoise.
|
| Even if one only has room for a 22-foot vertical there are lots of
| better choices.
|
| I agree with Jim. Put up a dipole and spend the leftover $395 on beer.
| --
| 73,
| Vic, K2VCO
| Fresno CA
| http://www.qsl.net/k2vco
| _______________________________________________
| Elecraft mailing list
| Post to: ***@mailman.qth.net
| You must be a subscriber to post to the list.
| Subscriber Info (Addr. Change, sub, unsub etc.):
| http://mailman.qth.net/mailman/listinfo/elecraft
|
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| Elecraft web page: http://www.elecraft.com
|
|
|
| --
| No virus found in this incoming message.
| Checked by AVG Free Edition.
| Version: 7.1.408 / Virus Database: 268.13.17/505 - Release Date: 10/27/2006
|
|

[Mike Morrow]

Post by n2ey at aol.com ()
I would want a lot more info before spending any money.
The BB7V is priced at US$400. It's a 22 foot vertical aluminum radiator
with a nice mast clamp (mast not included) and a cylindrical feedpoint
device.
The big question is: What's in the feedpoint device?
... the "device" ... was a "black box" type "proprietary" antenna coupler.
The price was rather high ($300-400) and it was guaranteed "flat SWR"
between 3-30 Mhz....
BEWARE of ANY "MAGIC DEVICE" that makes these claims.
More than likely it is a large pile of bovine fecal matter that they
are feeding you!

That was about 25 years ago, and it was a QST review that exposed this scam. The x-ray showed some junk PCB board that had been potted with the 50 ohm resistor, so that it would appear to have circuitry, should someone actually x-ray the unit.

Post by n2ey at aol.com ()
I agree with Jim. Put up a dipole and spend the leftover $395 on beer.

No truer words have ever been written!

Even honestly described and advertised HF verticals without a very very very good radial system are terrible performers compared to a simple dipole. Commercial *portable* verticals are especially so, and are also usually absurdly expensive. An example of a money and power waster is the Outbacker-series with their "ground coupling" base for portable use. It is one of those $400 "systems" that performs very poorly, compared to a $5 dipole. I've done side-by-side testing of both on several occasions.

I was tempted to repeat the old saw about there being no such thing as a free lunch, but that would be wrong. The simple dipole is very close to being free, and it will normally way outperform any HF vertical no matter how much money is dumped into some expensive "exotic" or bogus design.

Reports of success using HF verticals with poor radial systems only show that sometimes contacts can be made with the poorest of radiators. Friends don't let friends use portable HF verticals!

73,
Mike / KK5F

[N2EY at aol.com ()]

Post by Sandy W5TVW
WARNING!!!!!!!!!
This same scheme (scam?) happened quite a few years ago. Don't remember the
name
of the "device", but is was a "black box" type "proprietary" antenna
coupler.

You may be thinking of the Maxx-Com Matcher.

Post by Sandy W5TVW
The price was rather high ($300-400) and it was guaranteed "flat SWR"
between 3-30 Mhz.

Less than 2:1 over the range. And it did!

Post by Sandy W5TVW
SO-239 input and two standoff insulators with wing nuts (output). Was said
to match a random wire or a balanced line dipole! Someone finally
"x-rayed" one and it turned out to be a dummy load actually. It was
enclosed in a cast aluminum "Bud box" and potted with some sort
of opaque epoxy if you took the lid off!

"Someone" was the ARRL Lab. They X-rayed the thing and then dissolved the
epoxy (a long and messy process), and found what was inside.

There was a toroidal transformer, some noninductive resistors, and some
circuit boards with ICs on them. The circuit boards were obviously scrapped boards
from some digital system or other, and performed no electrical function at
all. They simply looked good on the X-ray.

Post by Sandy W5TVW
They didn't last too long,

Not true.

Maxx-Com is still around:

http://www.maxx-com.com/InstallationInfo.html

with a bunch of products.

They claim 80% or better efficiency, which is absolute bunk on most
frequencies. However, if the wire length is right, it may be possible for the system to
be almost that efficient. (See below).


but long enough for the manufacturer to

Post by Sandy W5TVW
make a bundle! It was not guaranteed to radiate with high efficiency
but was guaranteed to have an input VSWR no greater than 2:1!
BEWARE of ANY "MAGIC DEVICE" that makes these claims.
More than likely it is a large pile of bovine fecal matter that they
are feeding you!
No, I didn't buy one, but in some "unusual installations" it was
tried on some commercial marine limited coast station installations.
The results were very mediocre no matter what 'antenna' was tried.
Low SWR....BUT! Not much radiation!

Here's how such a system *could* work on a few frequencies:

Suppose the matcher consists of a "T" or "pi" attenuator. The SWR of such a
system will not be worse than 2:1 if the attenuator is designed right. IIRC, a
3 dB attenuator will do the job.

Suppose an antenna with an impedance of 50 ohms is connected to the other
end. The attenuator loss will be minimum, and the SWR 1:1.

Such a system could be as efficient as 50% (!)

Of course if the attenuator is removed, the efficiency is 100%.

The big problem is that as you move away from those few perfect frequencies,
the losses grow enormously and the system efficiency goes way down.

Of course if you feed 100 watts into an antenna system with 5% efficiency,
the result is the same as feeding 5 watts to an antenna system with 100%
efficiency.

73 de Jim, N2EY


73 de Jim, N2EY

[Fred (FL)]

Oh yee of little faith, on non-counterpoise HF
Verticals! Some of those mentioned are real
junkers.

Back to subject - what type of ATTIC ANTENNAS are
good, for us living in restricted communities (no
antennas) - with attics?

B&W makes a "Folded Dipole", 7-30mhz, 45 feet long -
with supposed flat swr? Like $245. Our attic antenna
needs to be pretty much left by itself - no trips up
there to change frequencies. And 40 thru 10 would
be nice.

I'm suprised no-one mentioned the performance of
that octagonal sheet metal HF antenna that is
always advertised in QST.

I guess I could get my old ARRL Antenna Book out,
and build a trap dipole for the attic ......
Or stick a Buddipole up there.

....... Stealth <100W
Fred
N3CSY



____________________________________________________________________________________
Get your email and see which of your friends are online - Right on the New Yahoo.com
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[Vic K2VCO]

Post by Fred (FL)
Back to subject - what type of ATTIC ANTENNAS are
good, for us living in restricted communities (no
antennas) - with attics?
B&W makes a "Folded Dipole", 7-30mhz, 45 feet long -
with supposed flat swr? Like $245. Our attic antenna
needs to be pretty much left by itself - no trips up
there to change frequencies. And 40 thru 10 would
be nice.

This *is* resistively loaded. It is not a scam like some, but it is less
efficient than an ordinary dipole. A dipole as long as possible in the
attic, not parallel to wires/pipes if possible, and fed with ladder line
and a balanced tuner would be close to optimum.

Post by Fred (FL)
I'm suprised no-one mentioned the performance of
that octagonal sheet metal HF antenna that is
always advertised in QST.

It's poor. Like anything, it works to some extent. Again, a simple
dipole would be much better.

Post by Fred (FL)
I guess I could get my old ARRL Antenna Book out,
and build a trap dipole for the attic ......
Or stick a Buddipole up there.

A trap dipole might require a lot of adjustment due to coupling to
nearby conductors. It might be a complicated process to get a
reasonable SWR on many bands. It would be easier to just make a tuned
doublet and let the balanced tuner take care of it.

A buddipole would work, of course, but it is too short for good
efficiency on the lower bands and would require you to bound up the
stairs to adjust it whenever you changed bands.

[Sandy W5TVW]

My "usual" antenna on a quick setup afield is a 33' vertical wire hoisted by an MFJ-1910 33'
fibreglass telescopic pole. This wih a K1 and KAT1 internal tuner. It will "tune" with no radials
but the performance is lousy. Add one 33' radial and it gets much, much better. Add TWO 33'
radials and much better yet. If I add two more (a total of four 33' radials and it improves more
yet but not a large change. If I add more, hardly notice any change at all for the most part. All
radials out of #24 hookup wire and laid on the ground. This for 40 thru 15 meter operation. For 80
meter use a 66' antenna, 33' vertical and the rest to a nearby tree limb from top of the support
mast. Sort of an "inverted L". This with 2-4 radials 66' long. It "works" but isn't the best I
could do with a better antenna.
My trials of "whips" and short verticals has been dismal. They will "work" but somewhat poorly so
say the least. The MFJ pole and 33' wires seem to be the best setup especially in places where you
have trouble finding supports like the middle of a parking lot or field! It won't work where there
is a lot of 'foot traffic' or kids as they will constantly be fouling the radials!!
Tried all sorts of loading schemes with whips from 4' to 15' and results fair on higher bands
(15/20) but very marginal on 40 or lower.
also tried shortened "loaded" dipoles and again it "works" but poorly. Sometimes you get lucky.

Just my 2 cents worth on portable radiators when you are QRP afield.

73 to all,
Sandy W5TVW
----- Original Message -----
From: "Fred (FL)" <***@yahoo.com>
To: <***@mailman.qth.net>
Sent: Friday, October 27, 2006 8:27 PM
Subject: Re: [Elecraft] Attic Antenna


| Oh yee of little faith, on non-counterpoise HF
| Verticals! Some of those mentioned are real
| junkers.
|
| Back to subject - what type of ATTIC ANTENNAS are
| good, for us living in restricted communities (no
| antennas) - with attics?
|
| B&W makes a "Folded Dipole", 7-30mhz, 45 feet long -
| with supposed flat swr? Like $245. Our attic antenna
| needs to be pretty much left by itself - no trips up
| there to change frequencies. And 40 thru 10 would
| be nice.
|
| I'm suprised no-one mentioned the performance of
| that octagonal sheet metal HF antenna that is
| always advertised in QST.
|
| I guess I could get my old ARRL Antenna Book out,
| and build a trap dipole for the attic ......
| Or stick a Buddipole up there.
|
| ....... Stealth <100W
| Fred
| N3CSY
|
|
|
| ____________________________________________________________________________________
| Get your email and see which of your friends are online - Right on the New Yahoo.com
| (http://www.yahoo.com/preview)
|
| _______________________________________________
| Elecraft mailing list
| Post to: ***@mailman.qth.net
| You must be a subscriber to post to the list.
| Subscriber Info (Addr. Change, sub, unsub etc.):
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|
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|
|
|
| --
| No virus found in this incoming message.
| Checked by AVG Free Edition.
| Version: 7.1.408 / Virus Database: 268.13.17/505 - Release Date: 10/27/2006
|
|

[Dan Barker]

I had some good laughs reading the "review" of the tuner. The comparisons
are quite favorable. Of course, they were comparing their product to a
halfway dipole. I guess that meant a dipole halfway assembled, or maybe
halfway burried. They didn't say<g>. But anyhow, their pos is 80%-90% as
efficient. Also, I've never read a review before with no attribution.

15,000 suckers! P.T. Barnum was right (assuming they are telling the
truth!).

Dan / WG4S / K2 #2456

<snip>

Post by Sandy W5TVW
They didn't last too long,

Not true.

Maxx-Com is still around:

http://www.maxx-com.com/InstallationInfo.html

</snip>

[N2EY at aol.com ()]

Post by Mike Morrow
Even honestly described and advertised HF verticals without a very very
very good radial system are terrible performers compared to a simple dipole.

I disagree!

The situation is much more complex than that.

Commercial *portable* verticals are especially so, and are also usually
absurdly

Post by Mike Morrow
expensive. An example of a money and power waster is the Outbacker-series
with their "ground coupling" base for portable use. It is one of those $400
"systems" that performs very poorly, compared to a $5 dipole. I've done
side-by-side testing of both on several occasions.

Of course a lossy antenna system - vertical or not - will be bested by an
efficient one.

There's also the factor of pattern.

Verticals are often sold as "great for local or DX". And they are - local (up
to a few miles) via ground wave, and DX (beyond 1-2 thousand miles) by
low-angle radiation.

But for everything in between, a dipole is better.

Post by Mike Morrow
I was tempted to repeat the old saw about there being no such thing as a
free lunch, but that would be wrong. The simple dipole is very close to being
free, and it will normally way outperform any HF vertical no matter how much
money is dumped into some expensive "exotic" or bogus design.

Again, "it depends". For example, a quarter wave vertical on 20 meters is
only 16 feet high. With its base a few feet off the ground, and a dozen sloping
radials, it will do as well or better as a dipole 40-50 feet up - *if* it's in
a wide-open location.

I built such a vertical for portable use from EMT and PVC, and have had great
success with it on Field Day.

OTOH, a loaded 80 meter vertical with a few radials isn't going to compete
with a decent dipole.

73 de Jim, N2EY

[Ron D'Eau Claire]

Fred, N3CSY, asked:
"what type of ATTIC ANTENNAS are
good, for us living in restricted communities (no
antennas) - with attics?"

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

I have and excellent results with doublets. That's a center fed wire as long
as I had room for in the attic. In an apartment that was at least 33 feet,
perhaps a little more, by making it slightly "Z" shaped. It doesn't hurt to
bend the ends a bit; just try to keep the angles of the bends as large as
you have room for. I strung them "inverted V" style from the rafters with
the center up at the peak as much as possible. No RF ground is needed and
the antenna is quite efficient.

They were fed with invisible open wire line. I made it out of whatever wire
was handy for the part in the attic and the visible part was white wire-wrap
wire sold by RS and others. It's quite small, about #30. That's not ideal
for a feeder but then again my feed line was rather short, especially the
part inside the apartment. I tried to arrange the operating desk next to a
wall as nearly as possible under the center of the antenna. Directly above
the operating position, I used an ice pick to put two small holes in the
ceiling right where it joins the wall. The resulting holes are no larger
than those produced by hanging a picture. The holes were about 2 inches
apart. I used a miniature homebrew ATU that hung on the wall at a convenient
height. I positioned the holes to be directly above it. Most apartment
walls are white or nearly so the white wire wrap wire is invisible against
the wall. I ran two lengths, one for each side of the feeder, up the wall
and through the tiny holes into the attic. One or two staples held the wires
tightly against the wall. Thumbtacks that match the wall work FB too.
Drywall is a good insulator. Up in the attic I ran the two feed wires to the
center of the antenna. Bits of plastic cut from film cans, old plastic coat
hangars or whatever is handy made up the spacers. It is NOT necessary to
have the wires running exactly parallel. Just make sure they don't touch and
are sort of parallel to the center of the antenna.

I had visitors come to the "shack" and look all around for the feeders from
two feet away without seeing them until I pointed them out.

A better choice for the feeder wire might be white hookup wire (if you have
white walls), #20 or #22. If your walls are a different color, consider a
little touchup paint matching the walls to dip the wire in to color it
before installing the feeder. Touch the heads of a couple of thumbtacks with
the same paint to hold the wires securely against the wall. Two at the top
and two at the bottom are usually plenty.

I never had an apartment higher than two floors, but I worked a LOT of DX
running 5 to 15 watts on HF CW, mostly 40, 30, and 20 meters. Made a lot of
contacts running 2 watts with an HW-8 as well.

At 33 feet long, the antenna was "full sized" for 40 meters. On 80 it was
only slightly less efficient than a full half wave. On the higher bands it
was really FB. The biggest problems on 80 for me were, 1) Noise from the
electrical systems in the apartments including things like touch-lamps and
cheap dimmers. Most apartments have the power lines running around the
ceilings (grrrrrr) and 2) Since my highest apartment was on the second
level, the antenna was no more than 30 feet above the ground. That's very
low for an 80 meter antenna. But on the higher bands it worked great.

You can build that antenna for perhaps $10 if you buy the wire and regular
antenna insulators new. If you get creative about what to use for insulators
the only cost is the wire and a little time.

Ron AC7AC

[Ron D'Eau Claire]

Whups... At 33 feet long my antenna was full sized for 20 meters, not 40
meters as I wrote. It was still quite efficient on 40 - only a tiny bit less
efficient than a full size antenna - and would work short skip on 80. I
could usually get between 40 and 50 feet up by making the bent ends of the
Z about 5 feet or so long.

Ron AC7AC

[PE1E]

Is it something like 5-1000 ?
Can't find no indication wherever.

Peter, PE1E.

[k3yt at adelphia.net ()]

Larry originally asked about attic antennas and a
concrete tile roof.

I have both.

I am in Lot 1 next to the gate, and blackmailed my HOA
into outdoor HF antennas. I have a Cushcraft R7000 up,
which is a half wave trapped antenna, but no radials.
Works great.

But I also have antennas in my attic. And they get used. A lot.

My dipole for 20m has been used a lot and works well. My roof peak is
about 22 feet and I have 14 foot ceilings. The main part of the house is about 42x46 feet, so I have a straight shot of about 45 feet in my attic where I can run
the wire about 21 feet above the concrete slab.

The 20m dipole has been replaced by a dipole with an SGC SG-239 coupler at the feed point. All bands and no SWR on feedline.

Works quite well. No problem working Europe on 100 watts. Worked a bit od DX with the K2 barefoot too.

The other HF antenna in the attic is a TFD, or terminated folded dipole. This is 45 feet long and homebrewed. I got 2 watt carbon film resistors from eBay, and a 16/1 QRP balun. I used the information from the Cebik site. Basically a squashed terminated loop.

Excellent receiving antenna. I do a lot of SW broadcast listening, so this antenna is
used for my Palstar R30.

My attic antennas work fine. After Hurricane Frances and especially Wilma which passed right over my house, I didn't have any trouble checking into the SATERN net
to pass H&W. During Wilma I even I even checked in to the Hurricane Watch Net
and passed on my reading of 28.00 inches of mercury from my barometer to the NHC. This was while the eye of Wilma was over the house.

So attic antennas work. Just (as a lot of the fellows have pointed out) put up a doublet with as much wire as high as you can. And if you can afford to put one of those automatic couplers at the feedpoint(no SWR on the feedline).

My 2 cents, but from practical experience and 30 years of ham radio.

73 all de Bob K3YT

[g4ilo at qsl.net ()]

I'm surprised with all this talk of dipoles and doublets that no-one has
mentioned loops. I'm not an antenna expert, but it has always seemed to me
that the efficiency of an antenna is somewhat related to the amount of wire
in the radiating element.

You can get more wire in a loop round the periphery of an attic than you
will get in a dipole strung in the apex of it. It may not give a 50 ohm
match, but nor will the dipole except at one frequency. If you feed it with
ladder line and a balun, or a very short length of co-ax, feeder losses
will be kept to a minimum. That's what I use.

73 de Julian, G4ILO. K2 #392
G4ILO's Shack: http://www.g4ilo.com

[David Cutter]

Julian

I agree with your sentiment. My 'doublet' was nearly a loop, ie it followed
the beams around the loft. The ends were left open, about a foot apart.

David
G3UNA

----- Original Message -----
From: <***@qsl.net>
To: <***@mailman.qth.net>
Sent: Saturday, October 28, 2006 12:22 PM
Subject: RE: [Elecraft] Attic Antenna

Post by g4ilo at qsl.net ()
I'm surprised with all this talk of dipoles and doublets that no-one has
mentioned loops. I'm not an antenna expert, but it has always seemed to me
that the efficiency of an antenna is somewhat related to the amount of wire
in the radiating element.
You can get more wire in a loop round the periphery of an attic than you
will get in a dipole strung in the apex of it. It may not give a 50 ohm
match, but nor will the dipole except at one frequency. If you feed it with
ladder line and a balun, or a very short length of co-ax, feeder losses
will be kept to a minimum. That's what I use.
73 de Julian, G4ILO. K2 #392
G4ILO's Shack: http://www.g4ilo.com
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[Jeff]

...My 'doublet' was nearly a loop, ie it followed
the beams around the loft. The ends were left open, about a foot apart...

I have some questions for the group. How would one decide whether the ends
should be left open, versus connected together to make a loop? (I never
could figure out how to model antennas using EZNEC. It should be called
HARDNEC.) Does it make a lot of difference? Using a tuner near the
feedpoint, which way would give a better match on more bands (160-10m), open
or closed ends? Which way would yield stronger signals in the most
directions? Is it the case that, below a certain total wire length, the
ends should be left open, but above that length, they should be connected
together? I guess the only way an indoor antenna of typical length would
match on 160m, even with a tuner, would be if the ends were connected
together and the whole thing was treated as a very bent end-fed wire working
against ground and a counterpoise.

Thanks & 73,
Jeff, WB5GWB
Long Island, NY
K2 #821

[David Cutter]

Jeff

Answering your last question first:
for top band and 80m mainly (actually, it worked on all bands) I joined the
feeders together into one terminal of my Drake tuner and the other I took
thro some tv coax (shorted) back up thro the ceiling, out to the soffit
board and straight down to a ground spike (brass curtain rods) and lots of
radials in the front garden. This was then a heavily top loaded vertical
and worked very well. The single outdoor brown wire spaced off the brick
wall about a foot was almost unnoticeable and a friend thought it was just
the tv coax that had come unclipped.

Back to the invertedV/doublet/loop bird's nest: I could model it in EZNEC
if I had a few minutes, but I am sure the results will be impenetrable:
there will be lobes going in all sorts of directions at all sorts of angles.
What will be a problem is modelling the house and structure which is beyond
me. Frankly, as the man said: I don't give a d*mn. As radio amateurs we
are interested in getting signals in and out and the performance of simple
antennas is just the joy of working the world and that's what I did. Be
aware of the noise picked up from the house mains and the interference you
can put into the mains. I used to modulate the lights on 20m. Look out for
high voltages - use heavy gauge insulated house wire (it's more efficient)
and insulate any bare wire ends.

As to shorting or opening the ends: it changed the range of frequencies that
could be matched. I started making a table of strength of signals from
various directions with open or short and with feeding from corners or apex,
but the combinations were endless and of course change endlessly with
frequency and band conditions. I gave up after a few trials. In its
vertical configuration I got more dx which was to be expected and I think I
left it like that.

Just enjoy getting out.

David
G3UNA

----- Original Message -----
From: "Jeff" <***@optonline.net>
To: <***@mailman.qth.net>
Sent: Saturday, October 28, 2006 9:19 PM
Subject: [Elecraft] Attic Ant.-Closed Loop vs. Open Ends?

Post by Jeff

...My 'doublet' was nearly a loop, ie it followed
the beams around the loft. The ends were left open, about a foot apart...

I have some questions for the group. How would one decide whether the ends
should be left open, versus connected together to make a loop? (I never
could figure out how to model antennas using EZNEC. It should be called
HARDNEC.) Does it make a lot of difference? Using a tuner near the
feedpoint, which way would give a better match on more bands (160-10m), open
or closed ends? Which way would yield stronger signals in the most
directions? Is it the case that, below a certain total wire length, the
ends should be left open, but above that length, they should be connected
together? I guess the only way an indoor antenna of typical length would
match on 160m, even with a tuner, would be if the ends were connected
together and the whole thing was treated as a very bent end-fed wire working
against ground and a counterpoise.
Thanks & 73,
Jeff, WB5GWB
Long Island, NY
K2 #821
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[N2EY at aol.com ()]

In a message dated 10/27/06 10:05:38 PM Eastern Daylight Time,

Post by Vic K2VCO

Post by Fred (FL)
B&W makes a "Folded Dipole", 7-30mhz, 45 feet long -
with supposed flat swr? Like $245. Our attic antenna
needs to be pretty much left by itself - no trips up
there to change frequencies. And 40 thru 10 would
be nice.

This *is* resistively loaded. It is not a scam like some, but it is less
efficient than an ordinary dipole.

It is a version of the T2FD, which has been discussed extensively all over
the 'net.

The best discussion I have seen is on the W4RNL (Cebik) website.

The efficiency of a T2FD varies over its frequency range. At the top end it
may be only a few dB less than a dipole of the same size, while at the bottom
end it is much less efficient. See the graphs on W4RNL's site - they're not
pretty.

While it *is* possible to make contacts with an inefficient antenna, remember
that the T2FD is much less efficient than a dipole of the same size, erected
in the same place.

The T2FD isn't new - it's been around since the late 1940s, and was
originally meant for receiving applications where its low efficiency wasn't really an
issue. It finds use in some military and government applications where its
broadband nature is essential (ALE, spread spectrum). The military and government
folks get around its inefficiency by running more power. Lots more power!

OTOH a T2FD can give you the QRP experience with a 100 watt rig.

For normal ham use it is a very poor choice, IMHO. A trap dipole or tuner-fed
dipole of the same size will do much better.

If you really want to try one in your attic, one can be homebrewed for much
much less than $245. Wire, plastic insulators, homemade balun, noninductive
resistors. Doesn't have to be weatherproof in the attic.


A dipole as long as possible in the

Post by Vic K2VCO
attic, not parallel to wires/pipes if possible, and fed with ladder line
and a balanced tuner would be close to optimum.

Agreed. Trap dipole is a second choice. Traps can be made easily from coax
and PVC pipe. You need a dip meter, though.

73 de Jim, N2EY

[Don Wilhelm]

Peter,

The Impedance range that the KAT2 will match will be greater on the higher
bands than the lower (just because of the math in the formulas for impedance
of inductors and capacitors). So I hesitate to guess at an answer becuase
you did not specify a frequency - I can add up the inductor and capacitor
values and give a range for each.

With a bit of work with a program like TLW (www.arrl.org), one could
determine the impedance range for each band. It is an L network tuner with
a series inductor range from 0 to 20.62 uH in 0.16 uH steps; while the shunt
capacitor can range in value from 0 to 2423 pf in 10 to 12 pf steps. The
shunt capacitor can be at either end of the inductor. Only the min and max
values need to be entered for each component and configuration, so there
would be 8 calculations for each band of interest.

All in all, it is a wide impedance range, but will be more restricted on 160
meters than on 10 meters. This same principle applies to all Elecraft
tuners and to other manufacturers of similar L network designs.

73,
Don W3FPR

Post by n2ey at aol.com ()
-----Original Message-----
Is it something like 5-1000 ?
Can't find no indication wherever.
Peter, PE1E.

[PE1E]

Thanks Don.

I found that the my KAT2 tunes about everything ( endfed long- and
shortwires, random length wire verticals with and without radials ( 100' asl
! ) on 80-40-20-15 where my LDG 200 Pro ( automatic atu ) fails definitely.

LDG 200 claims to match ~ 5-1K and in order to judge the misperformace of
my LDG200 I want to know the Z ranges on 80-4-20 of my KAT2, so that I can
claim a LDG refund or repair.

BTW, and a bit OT, I presume an external KAT 100 fits 100 W continuous.
Could the KAT100 withstand 250 W SSB( speech SSB only, no CW no FM ) , if my
sig is not rf clipped ( my old Datongs rf clippers ....) and my
transmissons are short ?
If so, I'll get rid of the LDG and buy me a KAT100.

Peter, PE1E


----- Original Message -----
From: "Don Wilhelm" <***@earthlink.net>
To: "PE1E" <***@chello.nl>; <***@mailman.qth.net>
Sent: Saturday, October 28, 2006 5:02 PM
Subject: RE: [Elecraft] Z range KAT2 ?

Post by PE1E
Peter,
The Impedance range that the KAT2 will match will be greater on the higher
bands than the lower (just because of the math in the formulas for

impedance

Post by PE1E
of inductors and capacitors). So I hesitate to guess at an answer becuase
you did not specify a frequency - I can add up the inductor and capacitor
values and give a range for each.
With a bit of work with a program like TLW (www.arrl.org), one could
determine the impedance range for each band. It is an L network tuner

with

Post by PE1E
a series inductor range from 0 to 20.62 uH in 0.16 uH steps; while the

shunt

Post by PE1E
capacitor can range in value from 0 to 2423 pf in 10 to 12 pf steps. The
shunt capacitor can be at either end of the inductor. Only the min and max
values need to be entered for each component and configuration, so there
would be 8 calculations for each band of interest.
All in all, it is a wide impedance range, but will be more restricted on

160

Post by PE1E
meters than on 10 meters. This same principle applies to all Elecraft
tuners and to other manufacturers of similar L network designs.
73,
Don W3FPR

Post by n2ey at aol.com ()
-----Original Message-----
Is it something like 5-1000 ?
Can't find no indication wherever.
Peter, PE1E.

[Vic K2VCO]

Post by PE1E
I found that the my KAT2 tunes about everything ( endfed long- and
shortwires, random length wire verticals with and without radials ( 100' asl
! ) on 80-40-20-15 where my LDG 200 Pro ( automatic atu ) fails definitely.
LDG 200 claims to match ~ 5-1K

It's not as simple as that. The impedance may be more or less reactive,
and the reactance can be either capacitive or inductive. I would expect
that tuners of different design might work better or worse with
particular combinations of resistance and reactance.

Post by PE1E
BTW, and a bit OT, I presume an external KAT 100 fits 100 W continuous.
Could the KAT100 withstand 250 W SSB( speech SSB only, no CW no FM ) , if my
sig is not rf clipped ( my old Datongs rf clippers ....) and my
transmissons are short ?
If so, I'll get rid of the LDG and buy me a KAT100.

Keep in mind that the KAT100 requires a K2. So if your 250 watts comes
from a QRP K2 plus amplifier, it would work. But if you're planning to
use a different transceiver, it would not.

I believe that the KAT100 is exactly the same as the KAT2 in terms of
network values and algorithms; so if your KAT2 matches everything so
should the KAT100!

[Jeff]

Post by PE1E
I found that the my KAT2 tunes about everything ( endfed long- and
shortwires, random length wire verticals with and without radials ( 100' asl
! ) on 80-40-20-15 where my LDG 200 Pro ( automatic atu ) fails

definitely...

In case anyone is considering which autotuner to buy, my results are similar
to Peter's. My KAT2 tunes my end-fed wire to a reasonable SWR on all bands,
whereas my LDG AT-100Pro falls short on 10m, despite changes in the length
of the wire.

73 & 72,
Jeff, WB5GWB
Long Island, NY
K2 #821

[Bill Johnson]

Jeff,

I agree with you. I cannot figure out Eznec.... Could be my brain doesn't
work the same way as the creator. I am a PC builder tech and etc., but that
program is designed for a different brain than mine. SO many use it but I
don't have the time or patience to figure it out. I worked in a usability
lab while designing desktop software for a very large corporation and this
would not satisfy us. It is NOT intuitive in my opinion! There's way too
much learning and putzin' to get it to work.


Bill
K9YEQ

K2-35 & 5279; KX1-35/3080
___________________________________

Subject: [Elecraft] Attic Ant.-Closed Loop vs. Open Ends?

...My 'doublet' was nearly a loop, ie it followed
the beams around the loft. The ends were left open, about a foot apart...

...(I never[WJ] could figure out how to model antennas using EZNEC. It
should be called[WJ] HARDNEC.) Does it make a lot of difference? [WJ] ...

Thanks & 73,
Jeff, WB5GWB

[Larry]

I agree with you. I cannot figure out Eznec.... Could be my brain doesn't
work the same way as the creator.

...(I never[WJ] could figure out how to model antennas using EZNEC. It
should be called[WJ] HARDNEC.) Does it make a lot of difference? [WJ] ...


I had the same problem until I went to the HELP menu. Under HELP there
are three tutorials. If you go through each one then you get a good
feel on how the program works.
73,
Larry, KB5DXY
K1 #2269 (in progress)

[ron]

ok, we have established that many of you cannot, like me, use the
software. (smile)

Who can answer the topic: "closed loop or open ends"?

Ron, wb1hga

Post by Bill Johnson
I agree with you. I cannot figure out Eznec.... Could be my brain doesn't
work the same way as the creator.

[Bill Johnson]

I gave up on LDG after having the Elecraft tuners. I was very disappointed.
The only non elecraft tuner I am successfully using is a remote SGC for a
ladder line fed off-center lazy L with an elevated ground plane which while
it tunes, doesn't work squat. I am pulling that one down and going with a
much larger loop.


Bill
K9YEQ

K2-35 & 5279; KX1-35/3080
___________________________________

[N2EY at aol.com ()]

In a message dated 10/27/06 4:38:23 PM Eastern Daylight Time,

Post by Stuart Rohre
The Diamond bottom tube may, (and likely) contains a broad band ferrite
cable choke.

Probably - to keep RF off the outside of the coax. Such a choke would cost a
few dollars at most.

Or there may be a combination trap/ loading coil such as used

Post by Stuart Rohre
on some tri band beams for multibands.

No, that wouldn't work.

Traps are used in the radiator itself, not at one end.

The BB7 claims SWR of less than 2:1 over the entire range. Traps and loading
coils won't do that.

It's resistively loaded.

73 de Jim, N2EY

[Vic K2VCO]

Post by N2EY at aol.com ()
In a message dated 10/27/06 4:38:23 PM Eastern Daylight Time,

Post by Stuart Rohre
The Diamond bottom tube may, (and likely) contains a broad band ferrite
cable choke.

Probably - to keep RF off the outside of the coax. Such a choke would cost a
few dollars at most.

Actually, a choke on the coax would *prevent* the antenna from working
unless it was mounted on a metal mast. It needs a counterpoise and the
coax shield provides it unless a mast or radials are present.

This is actually similar to the 'e-h' antenna, in which the alleged
'antenna' at the end of the feedline serves to tune the shield of the
feedline to resonance. The shield actually does the radiating. Adding
a bead balun to an e-h antenna causes the antenna to stop working and
the balun to get hot! No, I don't want to start a thread on this
antenna either!

In the Diamond antenna, the feedline is only half of the antenna, with
the 22-foot radiator being the other half and the resistor smoothing out
the SWR variations.

[N2EY at aol.com ()]

In a message dated 10/29/06 11:12:34 AM Eastern Standard Time,

Post by Vic K2VCO

Post by N2EY at aol.com ()
In a message dated 10/27/06 4:38:23 PM Eastern Daylight Time,

Post by Stuart Rohre
The Diamond bottom tube may, (and likely) contains a broad band ferrite
cable choke.

Probably - to keep RF off the outside of the coax. Such a choke would cost

a

Post by N2EY at aol.com ()
few dollars at most.

Actually, a choke on the coax would *prevent* the antenna from working
unless it was mounted on a metal mast. It needs a counterpoise and the
coax shield provides it unless a mast or radials are present.

Agreed. Note that in the literature, the unit is shown on a metal mast.

Post by Vic K2VCO
This is actually similar to the 'e-h' antenna, in which the alleged
'antenna' at the end of the feedline serves to tune the shield of the
feedline to resonance. The shield actually does the radiating. Adding
a bead balun to an e-h antenna causes the antenna to stop working and
the balun to get hot! No, I don't want to start a thread on this
antenna either!

Good idea.

Post by Vic K2VCO
In the Diamond antenna, the feedline is only half of the antenna, with
the 22-foot radiator being the other half and the resistor smoothing out
the SWR variations.

Or the mast.

So what's probably in the "matcher" is really just a resistor.

$400 for 22 feet of tubing, a mast clamp, and a nice noninductive resistor.

73 de Jim, N2EY

[Todd Fonstad]

Greetings,

It is interesting that this topic has arisen now, as I am wrestling with
some of the same challenges previously posted. I recently remarried and
moved across town to =91her house=92 I bought half of it =85 the north =
half :). I
put up a 110' long attic loop at about 25' above ground which is fed =
with a
short length of 300 ohm ladder line down through the ceiling to my =
shack. It
works very well from 40M on up, but although the K2's ATU will 'tune' =
itself
for 80M and even 160M duty, the loop is essentially a dummy load on =
those
low bands.=20

I would like to try to cut the loop at its center so as to have a
'convoluted doublet' (for lack of a better term) 55' long per side. I =
think
it would do relatively well on 80M but I have no idea what effect doing =
so
would have on noise levels and efficiency on the other bands.=20

I'm trying to avoid extensive experimentation. The low head room and the
thick insulation (I have to put plywood sheets down to avoid going down
through the ceiling) make negotiating the attic very difficult.=20

The main challenge is finding the exact center of the loop opposite the
feedpoint. There is no way this 63-year-old body is going to measure =
every
inch of the antenna to find this point where I would make the cut. Does
anyone have an 'elegantly-crafted' method of finding this point, perhaps
electronically?

Best regards,
Todd
N9NE
Oshkosh, WI



--=20
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.408 / Virus Database: 268.13.17/505 - Release Date: =
10/27/2006
=20

[Ron D'Eau Claire]

Can't help you with an "after the fact" method of measuring the center, but
my approach wherever I've had to string up a doublet that wasn't in a
straight line is to first cut it over-length with equal lengths on each side
of the feed point.

Then I install it working where I'll put the shortest side first. Install
it, cut it to length, and measure what I cut off. Then I cut that off of the
other end and install that side.

Truth to tell, where you feed it has little bearing on the operation,
particularly in an attic doublet, as long as it's not at one end (unless
it's 1/2 wave long <G>). The building will unbalance it and it doesn't
really need to be balanced. That's why leaving the balun out of the system
usually has no effect on the signal; sometimes it's an improvement! Balance
helps reduce the feeder radiation, but such radiation usually doesn't hurt.
Besides in an attic installation, the feeder length is pretty short anyway.

Ron AC7AC


-----Original Message-----
Greetings,

It is interesting that this topic has arisen now, as I am wrestling with
some of the same challenges previously posted. I recently remarried and
moved across town to 'her house' I bought half of it . the north half :). I
put up a 110' long attic loop at about 25' above ground which is fed with a
short length of 300 ohm ladder line down through the ceiling to my shack. It
works very well from 40M on up, but although the K2's ATU will 'tune' itself
for 80M and even 160M duty, the loop is essentially a dummy load on those
low bands.

I would like to try to cut the loop at its center so as to have a
'convoluted doublet' (for lack of a better term) 55' long per side. I think
it would do relatively well on 80M but I have no idea what effect doing so
would have on noise levels and efficiency on the other bands.

I'm trying to avoid extensive experimentation. The low head room and the
thick insulation (I have to put plywood sheets down to avoid going down
through the ceiling) make negotiating the attic very difficult.

The main challenge is finding the exact center of the loop opposite the
feedpoint. There is no way this 63-year-old body is going to measure every
inch of the antenna to find this point where I would make the cut. Does
anyone have an 'elegantly-crafted' method of finding this point, perhaps
electronically?

Best regards,
Todd
N9NE
Oshkosh, WI

[Stuart Rohre]

Now this method is a bit convoluted, but you could put extra long leads on
an ohm meter that will measure low ohms. Start at the feedpoint with one
lead, and experimentally tap onto the antenna where you think the 55 foot
point is. If you have found the center, you will have the resistance of 55
feet of wire indicated on your meter. You likely know the gauge of your
wire, thus, you can use a wire table to predict what 55 feet of that wires
should measure on the resistance scale. You will have to zero out the extra
long test leads you make to reach to the far side of the loop. The easiest
way is to make a test lead of 55 feet and then have short lead and the meter
with you as you seek the center on the far side.

Other means of accomplishing the same thing, are to find equal capacitance
point on far side to each side of the feed point insulator, or equal
inductance. However both of those methods may suffer from incidental
coupling within the attic. The low ohms method is done at DC to overcome
those disadvantages.

-Stuart
K5KVH

[Fred (FL)]

Looking like ELECRAFT should consider getting into the
STEALTH ANTENNA game. A stealth vertical perhaps, one
could just lean up against the home.
Or a gutter-shaped antenna, that would easily attach
to one's home front facia. There's certainly
interest and need for one.

Fred
N3CSY
....displaced Buffalonian



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[Stuart Rohre]

Hi antenna challenged fellow hams. You can do your own stealth gutter
antenna these days.

Two easy ways: 1) Get a combination of metal gutter and one short
section of plastic gutter to join two metal halves of a dipole. Remember,
you can use shorter than quarter wave lengths of elements, since their cross
section is large compared to wavelength.

2) Even easier: Get all plastic. Lay dipole elements in bottom of plastic
gutter. Even hook up wire can be used for elements. Glue them to corner of
gutter bottom that will be furtherest from the house. Better still, glue
them UNDER the gutter corner, so water in gutter will not stand on antenna
wire. Use 1/4 inch coax feed to feedpoint, or twin lead, again glued to
underside of gutter. Run it into soffit, and then to rig.
An all band tuner, will facilitate operations on multiple bands, especially
if the dipole is at least 60 per cent of a half wave for the lowest
frequency of interest.

Your nearest Lowe's or Home Depot is already a stealth antenna store, and
you did not know it. Even coax can be purchased there!

I regularly use insulators and standoff's from Home Depot's electric fence
department for various home antenna projects. They have a compression
spring for electric fence gates that is ideal for relieving stress in a
dipole element tied to a tree. Unlike a door spring which is extension
type, this spring will not elongate with use. At least, not as much as
extension springs.

Stuart
K5KVH