Attic Antenna

[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]

-----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]

[hidden email] 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
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[Bob Nielsen]

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

Bob, N7XY
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[N2EY]

-----Original Message-----
From: [hidden email]

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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[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



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[Vic K2VCO]

Stuart Rohre wrote:
> 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.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[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" <[hidden email]>
To: <[hidden email]>
Cc: <[hidden email]>
Sent: Friday, October 27, 2006 12:01 PM
Subject: Re: [Elecraft] Attic Antenna


| [hidden email] 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
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|
|
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| Checked by AVG Free Edition.
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|
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[Mike Morrow-3]

> 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?

Sandy wrote of an earlier example:

>... 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.

Vic wrote:

> 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
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[N2EY]

In a message dated 10/27/06 6:38:11 PM Eastern Daylight Time, [hidden email]
writes:


> 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.

> 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!
>
> 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.


> 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

>
> 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

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[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


 
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[Vic K2VCO]

Fred (FL) wrote:

> 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.

> 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.

> 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.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[N2EY]

In a message dated 10/27/06 7:33:23 PM Eastern Daylight Time, kk5f@earthl
ink.net writes:


> 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
> 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.

> 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
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[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)" <[hidden email]>
To: <[hidden email]>
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: [hidden email]
| You must be a subscriber to post to the list.
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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
|
|

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[Ron D'Eau Claire-2]

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

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[Ron D'Eau Claire-2]

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

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[k3yt-2]

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
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[g4ilo-2]

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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[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: <[hidden email]>
To: <[hidden email]>
Sent: Saturday, October 28, 2006 12:22 PM
Subject: RE: [Elecraft] Attic Antenna

> 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
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com 

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[PE1E]

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

Peter, PE1E.





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