Elecraft

Miniature self-supporting HF antennas

Classic

List

Threaded

48 messages Options

123

Vic Rosenthal

Re: Miniature self-supporting HF antennas

Vic Rosenthal

Re: Miniature self-supporting HF antennas

In reply to this post by Rick M0LEP-2

Well, I never operated from uncomfortable locations like above the tree
line, but my experience with portable antennas has been the same. Short
loaded antennas are not as good as wires. I prefer a dipole that can be
configured as a sloper, V, etc. I have a 33' collapsible fiberglass
pole that has been useful where there aren't enough trees. It's not
really suitable for backpacking, but smaller and lighter ones are available.

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 20 Jul 2015 12:46, Rick M0LEP wrote:

> So far, I've found nothing that comes close, and there's nothing
> more frustrating than getting to the top and then finding the antenna
> you have is doing a poor job. I now regard anything which relies on
> loading coils with deep suspicion. That coil's usually doing a fine
> job of converting RF to heat. One such antenna I tested against an
> inverted-V dipole turned out to be over 20dB down on the dipole for
> 40 metres.
>
> On Sun 19 Jul Wayne Burdick wrote:
>> But the search for the ideal miniature HF antenna continues:
>> something both very compact *and* highly efficient. Ideally it
>> would break down to a length of 8" or less, do an excellent job on
>> 20 meters and up, and earn a passing grade on 30 and/or 40 meters.

Rick M0LEP-2

Re: Miniature self-supporting HF antennas

Yes, I too prefer to get wire in the sky, and an inverted-V dipole works
pretty well. I have one with link breaks in it so that it can quickly be
changed for different bands (using 2mm or 3mm radio-control power
connectors for the breaks because they're very small, light, and make a
good connection), and a couple of fibreglass telescopic flag-poles. One
collapses to about 18 inches so fits in a back-pack easily enough, and
extends to 18 feet. The other (which only goes on shorter walks) is
about 28 foot long when extended, and about 3 foot 6 inches when
collapsed.

That set-up, however, doesn't fit Wayne's "breaks down to 8 inches"
ideal.

On Mon 20 Jul Vic Rosenthal wrote:
> I prefer a dipole that can be configured as a sloper, V, etc. I have a
> 33' collapsible fiberglass pole that has been useful where there
> aren't enough trees. It's not really suitable for backpacking, but
> smaller and lighter ones are available.

--
73, Rick, M0LEP (KX3 #3281)
Simony's eyes gleamed with the gleam of a man who had seen the
future and found it covered with armour plating.
-- (Terry Pratchett, Small Gods)

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: Miniature self-supporting HF antennas

In reply to this post by Tony Estep

One of the better sources of information and portable antennas is found
at http://www.dj0ip.de/antennas/ <http://www.dj0ip.de/antennas/>
Rick has some extensive test results on baluns and portable antennas on
his website. His OFCD antenna is an ideal back packing antenna covering
most all bands with a very reasonable tuner.

73 Bob, K4TAX

On 7/19/2015 9:51 PM, Tony Estep wrote:

> On Sun, Jul 19, 2015 at 9:12 PM, Don Wilhelm <[hidden email]> wrote:
>
>> Richard,
>>
>> Two properly spaced and phased radiators....
> =============
> I have a terrific wire-beam antenna that rolls up into a package that
> weighs only a couple of pounds. However, it requires one rope into a tree
> or other type of sky-hook.
>
> It is good for 20, 17, 15, 12 and 10 and is bi-directional. It's a form of
> W8JK, but is fed at the end and has series capacitors in each radiator to
> make it work over a 2:1 frequency range. I designed it with EZNEC and I'll
> send the model to anybody who wants it.
>
> It's fed with window line and requires a balun at the transmitter. It takes
> a good tuner to match it, but the Elecraft tuners can do the job.
>
> Anyway, it doesn't meet Wayne's request for a free-standing antenna, but
> it's a cool field-day antenna, especially here in the middle of the country
> where a bi-directional antenna is a good thing.
>
> Tony KT0NY
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
>
>

Niel Wiegand

Re: Miniature self-supporting HF antennas

In reply to this post by wayne burdick

My favorite all around travelling/hiking KX3 antenna is a 20 mtr endfed
half wave (EFHW) wire fed with an electrical quarter wave of TV
twinlead. See
http://w0vlz.blogspot.com/2012/06/another-portable-antenna.html With the
KX3/KXAT3 it will load up on 40, 30, 20, 17 and 10.

My 20 meter zepp is light weight and it only needs one support,
especially when deployed as an inverted V. I've made use a large bush
for a support before but usaully I'm familiar enough with the location
that I know whether I'll find a tree or not. If not, I carry along a 16'
crappie pole (cheap, light and collapses to less than 4') and some extra
nylon cord for guy lines.

Niel - W0VLZ

> Hi all,
>
> Have you found the "perfect" above-the-treeline backpacking antenna for use with your KX3 or other small rig?
>
> <snip>
>
> But the search for the ideal miniature HF antenna continues: something both very compact*and* highly efficient. Ideally it would break down to a length of 8" or less, do an excellent job on 20 meters and up, and earn a passing grade on 30 and/or 40 meters.
>
> One other key factor, at least with the KX3/KX1/K1 genre, is to take maximal advantage of the rig's internal ATU. A wide-range ATU (such as the KXAT3) can turn a narrow-banded antenna into one that covers a full band or even multiple bands, within limits. One general approach is to coarse-tune the antenna's own inductance, then let the ATU do cleanup.
>
> <snip>
>
> 73,
> Wayne
> N6KR
>

alorona

Verticals on mountaintops

In reply to this post by Jim Brown-10

[I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]
When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle.
But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop.
Al W6LX

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim Brown-10

Re: Verticals on mountaintops

Hi Al,

As it happens, W6GJB and I are building a custom 80M vertical for FD use
on a mountaintop. As part of the design process, I've compared it to an
inverted Vee at the height where we could rig it without trees. The
model, of course, is for "flatland," and while HFTA can tell us how
being on that mountain affected the horizontally polarized inverted Vee,
we have no comparable modeling for a vertically polarized antenna. So I
asked Dean Straw, N6BV, retired ARRL Antenna Book editor and author of
HFTA how he thought being on the mountain might affect the vertical. His
answer was "I don't have a guess."

Our vertical will be built from that modular army-surplus mast that
comes in 4 ft sections that fit together with a 40 ft telescoping tube
mounted to the top, with a wire taped to it. We will feed it as a
vertical dipole, and there will be loading both at the bottom and top.
Not at all suitable for backpacking. :)

73, Jim K9YC

On Mon,7/20/2015 9:58 AM, Al Lorona wrote:
> [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]
> When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle.
> But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim Brown-10

Re: Miniature self-supporting HF antennas

In reply to this post by Niel Wiegand

On Mon,7/20/2015 7:34 AM, Niel Wiegand wrote:
> My favorite all around travelling/hiking KX3 antenna is a 20 mtr
> endfed half wave (EFHW) wire fed with an electrical quarter wave of TV
> twinlead. See
> http://w0vlz.blogspot.com/2012/06/another-portable-antenna.html With
> the KX3/KXAT3 it will load up on 40, 30, 20, 17 and 10.

Here's another way to do it.

http://k9yc.com/VerticalDipole.pdf

All you need is some wire, some coax, that PL259 adapter, and a clamp-on
ferrite core. Adjust the length of wire and the distance between the
wire and the ferrite choke so that each are a quarter-wave. This antenna
can be rigged horizontally, vertically, or sloping, depending on the
available skyhooks.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Lynn W. Taylor, WB6UUT

Re: Verticals on mountaintops

In reply to this post by alorona

Keep in mind that the self-supported antenna may not be on a mountaintop.

73 -- Lynn

On 7/20/2015 9:58 AM, Al Lorona wrote:
> [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Elecraft mailing list

Re: Verticals on mountaintops

In reply to this post by alorona

If you are really connected to the earth and the resistance of the earth is really infinite then your efficiency is zero and it has the same effect as if you only have a shielded wire connected to the radiator. But this is impossible in real life, but is you install a counterpoise that is resonant at your frequency then you may radiate well. Remember that antennas have directivity in both azimuth and elevation. Read the ARRL Antennna Book over and over until you understand it if you want a good antenna. Your efficiency from your antenna connector on depends on the resistance of your counterpoise connection, your counterpoise and the length of your radiator. You get full credit for the radiator from the feed point to the loading coil and some credit for the whip length but very little for the coil itself, maybe a bit less than the coil length. Antenna installations always obey Ohm's law and the other laws of physics whether you understand them or not. Whether you want to believe or not! Save your desire to believe for religion, they say it works! Willis 'Cookie' Cooke,TDXS Contest Chairman K5EWJ & Trustee N5BPS
From: Al Lorona <[hidden email]>
To: "[hidden email]" <[hidden email]>
Sent: Monday, July 20, 2015 11:58 AM
Subject: [Elecraft] Verticals on mountaintops

[I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]
When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle.
But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop.
Al W6LX

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Elecraft mailing list

Re: Verticals on mountaintops

In reply to this post by Jim Brown-10

If you feed your antenna as a dipole, then your counterpoise is the lower leg. Your radiation resistance will be low if your antenna is short. You need something to raise it to about 50 ohms which will be either a coil across the feed point or a capacitor. I have found that there are so few stations with good 80/75 meter antennas in Field Day and many sites are so noisy, either with man made noise or atmospheric noise that it is hardly worth the effort to erect an 80/75 antenna for Field Day unless you have a high transmitter count. Willis 'Cookie' Cooke,TDXS Contest Chairman K5EWJ & Trustee N5BPS
From: Jim Brown <[hidden email]>
To: [hidden email]
Sent: Monday, July 20, 2015 12:14 PM
Subject: Re: [Elecraft] Verticals on mountaintops

Hi Al,

As it happens, W6GJB and I are building a custom 80M vertical for FD use
on a mountaintop. As part of the design process, I've compared it to an
inverted Vee at the height where we could rig it without trees. The
model, of course, is for "flatland," and while HFTA can tell us how
being on that mountain affected the horizontally polarized inverted Vee,
we have no comparable modeling for a vertically polarized antenna. So I
asked Dean Straw, N6BV, retired ARRL Antenna Book editor and author of
HFTA how he thought being on the mountain might affect the vertical. His
answer was "I don't have a guess."

Our vertical will be built from that modular army-surplus mast that
comes in 4 ft sections that fit together with a 40 ft telescoping tube
mounted to the top, with a wire taped to it. We will feed it as a
vertical dipole, and there will be loading both at the bottom and top.
Not at all suitable for backpacking. :)

73, Jim K9YC

On Mon,7/20/2015 9:58 AM, Al Lorona wrote:
> [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]
> When the ground is perfect, that's the best case for a vertical antenna. If the ground becomes worse than ideal, then the losses increase and performance is not as good and the pattern changes: less radiation to the horizon and higher takeoff angle.
> But then, if the ground continues to get worse -- let it become the worst case, an insulator with zero conductivity-- don't the losses go to zero again? And does the pattern go to more like an isotropic, or ...??? If the antenna does look more like it's in free space, then this would support the statement that there's radiation below the horizon from a vertical on a mountaintop.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

David Gilbert

Re: Miniature self-supporting HF antennas

In reply to this post by Rick M0LEP-2

In general, properly built coils aren't nearly as bad as you say they
are. It is possible to build coils with a Q of several hundred, and if
you do the math you'll see that the resulting loss is essentially
trivial. It all depends on the rest of the antenna, and yes, a very
short antenna with a crummy coil in the wrong place is going to suck.
But some of the best antennas on the market right now use coil loading
very effectively.

Dave AB7E

On 7/20/2015 2:46 AM, Rick M0LEP wrote:

> So far, I've found nothing that comes close, and there's nothing more
> frustrating than getting to the top and then finding the antenna you
> have is doing a poor job. I now regard anything which relies on loading
> coils with deep suspicion. That coil's usually doing a fine job of
> converting RF to heat. One such antenna I tested against an inverted-V
> dipole turned out to be over 20dB down on the dipole for 40 metres.
>
> On Sun 19 Jul Wayne Burdick wrote:
>> But the search for the ideal miniature HF antenna continues: something
>> both very compact *and* highly efficient. Ideally it would break down
>> to a length of 8" or less, do an excellent job on 20 meters and up,
>> and earn a passing grade on 30 and/or 40 meters.

Rick M0LEP-2

Re: Miniature self-supporting HF antennas

The one I got bitten by was the one reviewed here:

http://www.eham.net/reviews/detail/1378

It isn't too bad for the top end of HF when most of the adjusting coil
is not involved, but performance drops off dramatically once more than
about a third of the adjustable coil is exposed. If you've got 100 watts
(or more) to drive it with then I guess you might get somewhere with it,
but with the KX3 it might as well have been a dummy load on 40 metres,
never mind with the add-on coils for the lower end of HF.

On Mon 20 Jul David Gilbert wrote:
> In general, properly built coils aren't nearly as bad as you say they
> are. It is possible to build coils with a Q of several hundred, and if
> you do the math you'll see that the resulting loss is essentially
> trivial. It all depends on the rest of the antenna, and yes, a very
> short antenna with a crummy coil in the wrong place is going to suck.
> But some of the best antennas on the market right now use coil loading
> very effectively.

--
73, Rick, M0LEP (KX3 #3281)

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Tony Estep

Re: Miniature self-supporting HF antennas

In reply to this post by David Gilbert

On Mon, Jul 20, 2015 at 3:56 PM, David Gilbert <[hidden email]>
wrote:

>
> ...properly built coils aren't nearly as bad as you say....

===========
True, but even with a high-Q coil a typical base-loaded antenna inevitably
has low efficiency. This is the consequence of the fact that a loaded
antenna has a very low radiation resistance, which magnifies the impact of
all other system losses. ON4UN's excellent book Low-band DXing has a
detailed analysis that can help you make the best choice of setup.

Tony KT0NY
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Elecraft mailing list

Re: Miniature self-supporting HF antennas

In reply to this post by David Gilbert

A good example is the Biddipole concept.
Mel, K6KBE

From: David Gilbert <[hidden email]>
To: [hidden email]
Sent: Monday, July 20, 2015 1:56 PM
Subject: Re: [Elecraft] Miniature self-supporting HF antennas

In general, properly built coils aren't nearly as bad as you say they
are. It is possible to build coils with a Q of several hundred, and if
you do the math you'll see that the resulting loss is essentially
trivial. It all depends on the rest of the antenna, and yes, a very
short antenna with a crummy coil in the wrong place is going to suck.
But some of the best antennas on the market right now use coil loading
very effectively.

Dave AB7E

On 7/20/2015 2:46 AM, Rick M0LEP wrote:

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Elecraft mailing list

Re: Miniature self-supporting HF antennas

Terrible spelling, Buddipole, Sorry.
Mel, K6KBE

From: Mel Farrer <[hidden email]>
To: David Gilbert <[hidden email]>; "[hidden email]" <[hidden email]>
Sent: Monday, July 20, 2015 2:38 PM
Subject: Re: [Elecraft] Miniature self-supporting HF antennas

A good example is the Biddipole concept.
Mel, K6KBE

From: David Gilbert <[hidden email]>
To: [hidden email]
Sent: Monday, July 20, 2015 1:56 PM
Subject: Re: [Elecraft] Miniature self-supporting HF antennas

In general, properly built coils aren't nearly as bad as you say they
are. It is possible to build coils with a Q of several hundred, and if
you do the math you'll see that the resulting loss is essentially
trivial. It all depends on the rest of the antenna, and yes, a very
short antenna with a crummy coil in the wrong place is going to suck.
But some of the best antennas on the market right now use coil loading
very effectively.

Dave AB7E

On 7/20/2015 2:46 AM, Rick M0LEP wrote:

Jim Brown-10

Re: Miniature self-supporting HF antennas

In reply to this post by David Gilbert

On Mon,7/20/2015 1:56 PM, David Gilbert wrote:
> It all depends on the rest of the antenna, and yes, a very short
> antenna with a crummy coil in the wrong place is going to suck. But
> some of the best antennas on the market right now use coil loading
> very effectively.

There was an excellent piece in QEX a year or two ago devoted to the
design of short loaded antennas. It was published in two parts -- one
dealt with measurement, the other with studying the effect of the
position of the loading coil.

The executive summary -- the part of the antenna carrying the greatest
current does the most radiating, and for most short antennas, that's the
part of the antenna closest to the feedpoint. The current distribution
depends on the electrical length, including that coil. A loading coil
near the feedpoint seriously degrades the radiation efficiency of the
antenna, because the current maxima is in the coil, but the coil doesn't
radiate! SO -- loading should be as far as possible from the feedpoint!
All of this was borne out by the measurments.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Ignacy

Re: Miniature self-supporting HF antennas

Small dimension and weight dictate thin wires, say gauge 26-28. A magnetic loop is relatively heavy for portable QRP.

Verticals made of piece of wire are great over salt water or when conditions are great. For support I use 25ft pole collapsible to 2 ft. Away from the sea, two long wires made of thin wire are best IMHO. Or one long wire with a shorter wire. I understand that hanging a long wire is harder than shooting a vertical.

When in VK I had 2 70 ft long wires just 20ft high, plus a 30ft vertical plus a couple of radials. This was far from water on a flat land. I could make an antenna from any combination of long wires, a radial or a vertical. Nearly always the best antenna was 2 long wires connected directly to a tuner, and very rarely one long wire with a vertical. In no case was the vertical with radials best.

The reason a long wire is better than a vertical (most of the time) is lower losses and more radiation at many angles. So a greater chance of success somewhere.

Ignacy, NO9E

David Gilbert

Re: Miniature self-supporting HF antennas

In reply to this post by Rick M0LEP-2

Yeah, that's a low Q coil on a short antenna ... it's not going to be
very efficient.

Dave AB7E

On 7/20/2015 2:35 PM, Rick M0LEP wrote:

> The one I got bitten by was the one reviewed here:
>
> http://www.eham.net/reviews/detail/1378
>
> It isn't too bad for the top end of HF when most of the adjusting coil
> is not involved, but performance drops off dramatically once more than
> about a third of the adjustable coil is exposed. If you've got 100 watts
> (or more) to drive it with then I guess you might get somewhere with it,
> but with the KX3 it might as well have been a dummy load on 40 metres,
> never mind with the add-on coils for the lower end of HF.
>
> On Mon 20 Jul David Gilbert wrote:
>> In general, properly built coils aren't nearly as bad as you say they
>> are. It is possible to build coils with a Q of several hundred, and if
>> you do the math you'll see that the resulting loss is essentially
>> trivial. It all depends on the rest of the antenna, and yes, a very
>> short antenna with a crummy coil in the wrong place is going to suck.
>> But some of the best antennas on the market right now use coil loading
>> very effectively.

David Gilbert

Re: Miniature self-supporting HF antennas

In reply to this post by Tony Estep

I never said anything about base loading. That's where most of the
current is, and therefore the most opportune location to create loss.

There's no current at the end (top), of course, so a loading coil does
no good at all there ... somewhere in between is generally best.

Dave AB7E

On 7/20/2015 2:37 PM, Tony Estep wrote:

> On Mon, Jul 20, 2015 at 3:56 PM, David Gilbert <[hidden email]>
> wrote:
>
>> ...properly built coils aren't nearly as bad as you say....
> ===========
> True, but even with a high-Q coil a typical base-loaded antenna inevitably
> has low efficiency. This is the consequence of the fact that a loaded
> antenna has a very low radiation resistance, which magnifies the impact of
> all other system losses. ON4UN's excellent book Low-band DXing has a
> detailed analysis that can help you make the best choice of setup.
>
> Tony KT0NY
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

123