(OT) EFHW Vertical Antenna

[stan levandowski]

Every so often, someone posts an inquiry here seeking info on a portable
-or otherwise 'non-permanent'- antenna for use either in the field or at
home under some restrictive conditions.

I'd like to offer the following Youtube demonstration to such listers
who might be interested.

It's not perfect but it sure held its own in this 'shootout' against a
135' OCF.

http://www.youtube.com/watch?v=uWkpQ785Pjo

73, Stan WB2LQF
KX1 #2411    K1#2994    K2# 6980    K3#5244     K9 #1 (Cocoa the
Chihuahua)
Everything is QRP, even the dog.

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[Mike Morrow-3]

Stan wrote:

> I'd like to offer the following Youtube demonstration to such listers
> who might be interested.

>  http://www.youtube.com/watch?v=uWkpQ785Pjo

That is an interesting demonstration, Stan.  I have a couple of questions.

It is stated that the VSWR was no greater than 1.4:1 on 40 through 10 meters.
But it appears to me that these figures report only the lowest VSWR that the
K2's ***ATU*** could produce, NOT the actual VSWR that existed on the antenna
side of the ATU.  That seems at best be a measure of K2 ATU performance.  It
says nothing substantive about the characteristics of the attached antenna. :-)
If that is correct, do you have any figures for the VSWR that the antenna
with transmission line actually presents to the tuner?  The impedance plots
from a good antenna analyzer would be most interesting.

Why use thin 20 awg wire along the mast as the radiator?  In my 35 years of
experimenting with portable wire antennas, I found nothing but trouble when
using such extremely small diameter wire.  Instead, for more than 15 years I've
used 14 awg Flexweave-tm which consists of 168 very fine strands of copper.
It is a dream to use, and it never suffers fatigue failure.  I've never had a
portable wire antenna to fail since I started using Flexweave.  It's available
bare or insulated, and either will tolerate frequent spooling and un-spooling
for the life of the antenna.

I also question the use of 22 awg wire in the toroidal transformer.  Such small
conductors represent just as much RF loss at QRP as at 200 watts.  Much larger
conductors would be appropriate there as well.

There is no advantage to small conductors in any HF antenna design, especially
for QRP use.  I also cringe at the RG-174 coax crowd. :-)

73,
Mike / KK5F
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[stan levandowski]

Hello Mike.  My EFHW vertical is resonant only at 20 meters.  The
*antenna* SWR is lousy everywhere else according to my MJF259 which
stops reporting at 25:1.  -- just as bad as my non-resonant-by-design
44' Cebik doublet with which I've worked the world, at 5 watts and
below. The internal tuners in my KX1, K1, and K2 all tune the antenna
between 1:1 and 1:4.  I've used this vertical with good results on 40
meters and *great* results on 30, 20, 17,12, and 10.

My use of *great* is within the following context:  I have little test
equipment and my background in electronics is truly 'amateur'; I'm still
learning after 51 years and I never seem to be able to learn enough,
fast enough  ;).    Hence the use of the word 'empirical' in the Youtube
description to underscore the casual nature of this rather interesting
comparison between W1ZMB's OCF  up in the clear and my new antenna toy
sitting on his deck.  All I can say is that the darn thing produces
great DX QSOs for me on my 5 watts or less and affords me a second
antenna option in my antenna restrictive community.  Sometimes, a signal
is louder on my doublet than the vertical or vice versa: a quick flip of
a switch and I can try the other antenna.  It's nice to have that
option.

The 9:1 UNUN I used (purchased from the Emergency Radio Club of
Honolulu) was my choice over a parallel tuned circuit because my goal
was to end up with the easiest and fastest antenna to put up and take
down and use.  I don't have to stand next to the antenna and tune a
capacitor this way.   I realize my choice might not be technically
optimum but once again, it reflects the goal I set for myself.

I'm using 20 gauge teflon coated wire because the 33' MFJ pole tapers to
an extremely thin final section - closer to an ultralight fishing pole.
Anything larger than 20 gauge starts to bend the pole's tip over.  In my
own experience - and I once again admit my technical weakness in the
subject area - I have experienced no difficulty with extremely thin wire
at the QRP levels I operate at.  In order to put less strain on the wire
during frequent set up/takedown I chose to wind it around homemade clips
as shown in the video which give me about an 18" diameter.  The video
shows how quickly it can be done with no tangle.

The 22 gauge toroid wire is what the Honolulu folks who designed the
UNUN used.  It seems to be a frequently occuring wire size in other EFHW
papers and construction articles I've read.  Again, I'm sorry that I
don't have the technical background to comment further.

  stan WB2LQF

On Sat, Nov 12, 2011 at 1:14 PM, Mike Morrow wrote:

>>  http://www.youtube.com/watch?v=uWkpQ785Pjo
>
> That is an interesting demonstration, Stan.  I have a couple of
> questions.
>
> It is stated that the VSWR was no greater than 1.4:1 on 40 through 10
> meters.
> But it appears to me that these figures report only the lowest VSWR
> that the
> K2's ***ATU*** could produce, NOT the actual VSWR that existed on the
> antenna
> side of the ATU.  That seems at best be a measure of K2 ATU
> performance.  It
> says nothing substantive about the characteristics of the attached
> antenna. :-)
> If that is correct, do you have any figures for the VSWR that the
> antenna
> with transmission line actually presents to the tuner?  The impedance
> plots
> from a good antenna analyzer would be most interesting.
>
> Why use thin 20 awg wire along the mast as the radiator?  In my 35
> years of experimenting with portable wire antennas, I found nothing
> but trouble when
> using such extremely small diameter wire.  Instead, for more than 15
> years I've
> used 14 awg Flexweave-tm which consists of 168 very fine strands of
> copper.
> It is a dream to use, and it never suffers fatigue failure.  I've
> never had a
> portable wire antenna to fail since I started using Flexweave.  It's
> available
> bare or insulated, and either will tolerate frequent spooling and
> un-spooling
> for the life of the antenna.
>
> I also question the use of 22 awg wire in the toroidal transformer.
> Such small
> conductors represent just as much RF loss at QRP as at 200 watts.
> Much larger
> conductors would be appropriate there as well.
>
> There is no advantage to small conductors in any HF antenna design,
> especially
> for QRP use.  I also cringe at the RG-174 coax crowd. :-)
>
> 73,
> Mike / KK5F

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[k6mgo]

Stan and group,

Just finished building my vertical antenna, and wanted to say it works as advertised. I built it on a 31' Jackite Flag pole that I had, I built my own UNUN with core from Palomar, and using 25' of RG-58 and the antenna mounted on my patio it tunes up on 40-10 meters using my MFJ auto tuner 929.

I like the idea of no radials the most, and while it's not as good as my indoor doublet in the garage, on 40 and 30 meters, on 20 and above, it is better. So, with both my antennas now, I can operate and have fun.

Thanks again for posting this Stan.

73, Bill, k6mgo