Cecil Moore wrote:
Denton wrote:
I picked up a used one last sprng, set it up about 3 ft off the ground in
the back yard...and took it back down within a couple of weeks.
Signals were way down compared to my 450 ohm ladder line fed 80 meter
doublet on all bands.

I had the same experience with a 1/4WL 40m vertical. Now I wish
I had run some A/B transmitting tests as well as the A/B
receiving tests

I thought you did that with N2EY . . ?

which the vertical flunked mainly due to an
extremely high noise level.

I did some of that sort of A/B testing between an elevated 1/4 wave 40M
GP and an 80/75/40M 130 foot end-fed inverted L a number of years ago
and the GP did not fare well at all. As it happened there wasn't much
of an electrical noise problem in the neighborhood then so QRN one way
or the other was not a term in this specific equation.

The vertcal leg of the inverted L was spaced about 20 feet from the
tower and was base-fed by a remotely controlled L/C tuner out in the
back yard, a USN surplus gun director selsyn motor cranked a big rotary
inductor which allowed me to QSY from 40 to 80/ 75. But the process ate
a minute or two to do which was a pain in the tush during the DX
contests I was into. Instantaneous band changing in that game matters.

The apex of the L was around 60 feet AGL. The 70 foot "horizontal" run
sloped down from the apex to about 35 feet AGL. The L worked quite well
on both bands, I could snipe JAs at will with just an SB-200 on either
band from here on the east coast when band condx were decent.

I decided that I had to put up some kind of 40M antenna so that I could
quickly QSY from 80/75 to 40 by simply flipping an antenna selector
switch which would get me away from the increasingly annoying "twist
the selsyn 30 turns" routine when band swapping.

So I built a textbook-classic 40M 1/4 wave GP which had a
self-supporting 35 foot +/- radiator. The base was at 35 feet AGL,
there were four downward-sloping wire radials. The whole thing perched
atop the roof of the abode. SWR over the entire band was essentally
unity.

Turned out to be a complete waste of time, money and effort. For
whatever reason or reasons there wasn't much difference in received
signal strength levels beteen the two antennas when I was listening to
long-haul DX like JAs and VK/ZLs on my end. But when I called them more
times than not they did not come back to me. I spent a couple intense
very early morings A/B swapping between the L tuned for 40M and the GP
QSOing the DX. In 90% of the cases they "heard me much better" when I
was using the L than they did when I used the GP. I took the GP down
and good riddance.

I'll leave the theoretical howcums of my experince to those of you who
are deep into the physics of electromagnetics. For my part another 1/4
wave HF GP just ain't gonna happen here again elevated with radials or
ground mounted with gazzilion radials.

.. . . half-wave verticals being a whole different ballgame . .

I'm thinking about putting the
vertical back up as a 1/4WL 30m vertical fed at the base with
an SGC-230 that I already have. Such an antenna should work
pretty well on 40m-10m, at least for transmitting.

Go for it and post your results.

--
73, Cecil http://www.qsl.net/w5dxp

w3rv

I'll leave the theoretical howcums of my experince to those of you who
are deep into the physics of electromagnetics. For my part another 1/4
wave HF GP just ain't gonna happen here again elevated with radials or
ground mounted with gazzilion radials. ..........................


Kinda weird. The one I used here worked great. And almost
identical specs. Mine was full size at 36 ft with 4 sloping radials.
The only thing I can think of to explain it , would be ground quality.
Evidentally, my ground quality must be pretty good compared to
many areas of the country. I know it's a good bit better than Cecils,
judging by the conductivity maps. If your's didn't work up to par,
I'd almost have to blame it on the radial system. I think you probably
needed a few more to equal what I had here. In fact, going by the
numbers, for a 1/4 wave at a 1/4 wave high, you really need 8 radials
to equal 120 on the ground. I judged my 4 radials as being equal to
about 60 radials for a ground mount. But...My conductivity rating in
this area is bordering on the "30" range being I'm not too far from the

coast. I know for sure Cecil would need more radials than mine for
the same performance, as his was half the height and his ground
rating is lower. .
My hunch is if you had 8 radials on the GP, it probably would have
done better.
My GP totally smoked the ground mount I had that used 32 radials.
No comparison at all. I've never tried 1/2 waves on the low bands,
except for extended inv-L's...I have run them 20m up though.
Work well there.
MK

wrote:
I'll leave the theoretical howcums of my experince to those of you who
are deep into the physics of electromagnetics. For my part another 1/4
wave HF GP just ain't gonna happen here again elevated with radials or
ground mounted with gazzilion radials. ..........................


Kinda weird. The one I used here worked great. And almost
identical specs. Mine was full size at 36 ft with 4 sloping radials.
The only thing I can think of to explain it , would be ground quality.
Evidentally, my ground quality must be pretty good compared to
many areas of the country. I know it's a good bit better than Cecils,
judging by the conductivity maps. If your's didn't work up to par,

Hi Mark. What's your/any definition of "par"in this context? What other
40M antenna did you A/B test against your GP on the air?

I'd almost have to blame it on the radial system. I think you probably
needed a few more to equal what I had here. In fact, going by the
numbers, for a 1/4 wave at a 1/4 wave high, you really need 8 radials
to equal 120 on the ground. I judged my 4 radials as being equal to
about 60 radials for a ground mount.

No surprise there.

But...My conductivity rating in
this area is bordering on the "30" range being I'm not too far from the
coast.

.. . maybe someday I really will download that map . . Not that I can do
anything about what it tells me about the ground condx in my particular
neighborhood . .

I know for sure Cecil would need more radials than mine for
the same performance, as his was half the height and his ground
rating is lower. .
My hunch is if you had 8 radials on the GP, it probably would have
done better.

Maybe, maybe not but realistic modeling elevated HF GPs would at least
provide some hints. Maybe.

From what I've seen, heard and read over the years there's a whole
bunch of smoke, mirrors and mythology wrapped around the effects of
radials as they relate to current-fed HF verticals. Reg Edwards
"endfeed.exe ' ditty looks like it debunks a bunch of the mythology. In
any event and with all due respect I'm not about to get into
nit-picking any of it.

The situation I described was a sort of very subjective A/B "shootout"
between my two 40M antennas as transmitting antennas and the so-far
strange and unexplained results I got and I seriously doubt that my
results would have been noticeably different if the GP had four more
radials. My voltage-fed inverted L seriously and consistently
outperformed the GP on long-haul contacts as a *transmitting* antenna
to the tune of at least one s-unit, sometimes more particulary into the
north Pacific, at the far end. But the two antennas seemed even-up when
*receiving* on my end. That's the issue Cecil brought up. The only
"radials" I had under the L was a three foot long #14 wire which ran
from the cold side of the tuner to a copper-plated eight foot steel
ground rod driven a few feet into the ground. It BOOMED. The GP did
not.

My GP totally smoked the ground mount I had that used 32 radials.
No comparison at all.

Yup.

I've never tried 1/2 waves on the low bands,
except for extended inv-L's...I have run them 20m up though.
Work well there.

Seems like they work nicely. So far my only measurable current-era
experience with true ground-mounted half-wave "dipoles" came about when
I operated portable for an extended period a few years ago and strung a
coax-fed 20M dipole up into a big maple tree with the bottom end of it
a foot or so above the ground. Lousy location, halfway down a hill on
one side of a mini-valley but "I worked every station I called". Heh.
My alternative antenna then was 475 feet of wire strung thru seven
trees "resonated" by some MFJ rotary inductor clunker or another which
was "gounded" by 75 feet of wire from my third floor shack to the
nearest patch of grass. RFI disaster site. Zero RFI with the dipole.


Anyway I'm on my way into a new location. Tiny property which will host
several voltage-fed HF verticals because of their minimum-size
footprints. Along with the verticals the property also hosts a rather
swampy bamboo farm. Big suckers too, maybe I can raise my own quad
spreaders. What do you 'spose the ground resitivity and permitivity
might be? Reg and Nec-Win- Plus want to know . . .

MK

w3rv

Brian Kelly wrote:
Cecil Moore wrote:
Denton wrote:
I picked up a used one last sprng, set it up about 3 ft off the ground in
the back yard...and took it back down within a couple of weeks.
Signals were way down compared to my 450 ohm ladder line fed 80 meter
doublet on all bands.

I had the same experience with a 1/4WL 40m vertical. Now I wish
I had run some A/B transmitting tests as well as the A/B
receiving tests

I thought you did that with N2EY . . ?

We did. From Cecil's QTH in Texas to mine here in suburban Philly I
could hear no
significant difference between the two antennas in A/B tests where I
didn't know
which antenna was being used (just A versus B).

But that's just one data point on one band over one path.

which the vertical flunked mainly due to an
extremely high noise level.

I did some of that sort of A/B testing between an elevated 1/4 wave 40M
GP and an 80/75/40M 130 foot end-fed inverted L a number of years ago
and the GP did not fare well at all. As it happened there wasn't much
of an electrical noise problem in the neighborhood then so QRN one way
or the other was not a term in this specific equation.

The vertcal leg of the inverted L was spaced about 20 feet from the
tower and was base-fed by a remotely controlled L/C tuner out in the
back yard, a USN surplus gun director selsyn motor cranked a big rotary
inductor which allowed me to QSY from 40 to 80/ 75. But the process ate
a minute or two to do which was a pain in the tush during the DX
contests I was into. Instantaneous band changing in that game matters.

The apex of the L was around 60 feet AGL. The 70 foot "horizontal" run
sloped down from the apex to about 35 feet AGL. The L worked quite well
on both bands, I could snipe JAs at will with just an SB-200 on either
band from here on the east coast when band condx were decent.

I decided that I had to put up some kind of 40M antenna so that I could
quickly QSY from 80/75 to 40 by simply flipping an antenna selector
switch which would get me away from the increasingly annoying "twist
the selsyn 30 turns" routine when band swapping.

So I built a textbook-classic 40M 1/4 wave GP which had a
self-supporting 35 foot +/- radiator. The base was at 35 feet AGL,
there were four downward-sloping wire radials. The whole thing perched
atop the roof of the abode. SWR over the entire band was essentally
unity.

Turned out to be a complete waste of time, money and effort. For
whatever reason or reasons there wasn't much difference in received
signal strength levels beteen the two antennas when I was listening to
long-haul DX like JAs and VK/ZLs on my end. But when I called them more
times than not they did not come back to me. I spent a couple intense
very early morings A/B swapping between the L tuned for 40M and the GP
QSOing the DX. In 90% of the cases they "heard me much better" when I
was using the L than they did when I used the GP. I took the GP down
and good riddance.

I'll leave the theoretical howcums of my experince to those of you who
are deep into the physics of electromagnetics. For my part another 1/4
wave HF GP just ain't gonna happen here again elevated with radials or
ground mounted with gazzilion radials.

I think the differences were two:

First, the ground plane with four radials wasn't all that hot, and the
lossy house was in the near field. The L wire was high-Z and its ground
wasn't all that important. Plus the ground was high conductivity moist
Aldan soil.

Second, the part of the GP with the most current, and therefore doing
the most radiating, was the bottom part. I don't know how high the
house roof was but it couldn't have been much more than 30-35 feet?

But the L wire on 40 meters was a full wave. High current was halfway
up the sloping part, and about halfway up the vertical part.

So you probably had less ground loss and some serious polarization
diversity. End result: they heard you better.

. . . half-wave verticals being a whole different ballgame . .

I'm thinking about putting the
vertical back up as a 1/4WL 30m vertical fed at the base with
an SGC-230 that I already have. Such an antenna should work
pretty well on 40m-10m, at least for transmitting.

Go for it and post your results.

Agreed

73 de Jim, N2EY

wrote:


Hi Mark. What's your/any definition of "par"in this context? What other
40M antenna did you A/B test against your GP on the air?

Directly, my 40m dipole at appx the same height as the base of the GP.
I also compared with the earlier ground mount with 32 radials, but
not directly, as the same radiator was used on both antennas.
When comparing the dipole and the ground mount vertical at 1500
miles, they were almost always about the same. Tested many times.
In comparison, the GP would always beat the dipole by 2 s units
at 1500 miles. Again, tested many times over a period of time.



But...My conductivity rating in
this area is bordering on the "30" range being I'm not too far from the
coast.

.. . maybe someday I really will download that map . . Not that I can do
anything about what it tells me about the ground condx in my particular
neighborhood .
.................................................. ..................

It also occurs to me that the ground off in the far field would effect
also. Being most all of this area is rated pretty well, that could be
a factor as far as low angle dx stuff... ??

I know for sure Cecil would need more radials than mine for
the same performance, as his was half the height and his ground
rating is lower. .
My hunch is if you had 8 radials on the GP, it probably would have
done better.

Maybe, maybe not but realistic modeling elevated HF GPs would at least
provide some hints. Maybe.

Dunno. I've modeled mine, and for it to mimic real life at this qth, I
always
had to boost the ground quality in the program.

From what I've seen, heard and read over the years there's a whole

bunch of smoke, mirrors and mythology wrapped around the effects of
radials as they relate to current-fed HF verticals. Reg Edwards
"endfeed.exe ' ditty looks like it debunks a bunch of the mythology. In
any event and with all due respect I'm not about to get into
nit-picking any of it.

Dunno. Haven't seen that yet... But I'm a pretty firm believer in what
I've seen written and graphed as far as the number of radials needed
to equal a certain performance of a ground mount. The lower in WL,
the more you need, of course.

The situation I described was a sort of very subjective A/B "shootout"
between my two 40M antennas as transmitting antennas and the so-far
strange and unexplained results I got and I seriously doubt that my
results would have been noticeably different if the GP had four more
radials. My voltage-fed inverted L seriously and consistently
outperformed the GP on long-haul contacts as a *transmitting* antenna
to the tune of at least one s-unit, sometimes more particulary into the
north Pacific, at the far end. But the two antennas seemed even-up when
*receiving* on my end.

*This* is the weird part to me... I've rarely seen antennas not act
reciprical as far as transmit/receive... Thats kinda unusual...

That's the issue Cecil brought up. The only
"radials" I had under the L was a three foot long #14 wire which ran
from the cold side of the tuner to a copper-plated eight foot steel
ground rod driven a few feet into the ground. It BOOMED. The GP did
not.

Hummm....Still the only rational explanation I can think of is the
GP needed more radials... Can't really think of any other reason,
unless maybe the general takeoff angle was a bit higher with the
GP, and again, that would tend to point to mediocre ground at , or
in the far field of the antenna. Can't really think of anything else,
unless maybe the radiator was a poor conductor, etc...Kinda doubt
that though...



I've never tried 1/2 waves on the low bands,
except for extended inv-L's...I have run them 20m up though.
Work well there.

Seems like they work nicely. So far my only measurable current-era
experience with true ground-mounted half-wave "dipoles" came about when
I operated portable for an extended period a few years ago and strung a
coax-fed 20M dipole up into a big maple tree with the bottom end of it
a foot or so above the ground. Lousy location, halfway down a hill on
one side of a mini-valley but "I worked every station I called". Heh.
..
All of my 1/2 wave verticals have been base fed so far. I usually use
the "gamma loop" type of feed. But...All those have been elevated,
not ground mount.

Anyway I'm on my way into a new location. Tiny property which will host
several voltage-fed HF verticals because of their minimum-size
footprints. Along with the verticals the property also hosts a rather
swampy bamboo farm. Big suckers too, maybe I can raise my own quad
spreaders. What do you 'spose the ground resitivity and permitivity
might be? Reg and Nec-Win- Plus want to know . . .

Dunno, but the conductivity map might give a general idea. You can d/l
those things somewhere. But...Forgot where I got them.. I've
got some I d/led that are in full color, and have separate charts for
the
various areas of the country. But there is also a little version in the

ARRL antenna handbook I think.. Texas is kinda weird as far as ground.
It's real good at the coast "30", but drops to 15, or even lower as you

venture north up into central-east Texas. But there is a hot zone that
runs up through Dallas, and father up into the midwest, that is rated
at 30. Cecil is in the poorer "middle" zone between the two good
parts.. It's quite possible my GP did well cuz of the decent
ground
quality both at the antenna, and farther away.
You should have seen my mobile on 40m at the beach a few months
ago. I was parked right on the water nearly, and using my maximum
length 14 ft antenna, with the loading coil at 8 ft up the whip.
"antenna
base at appx 64 inches from the ground, on the cab of the truck"
Absolutely was kickin butt...I was keeping up with home stations
running KW amps when yik yakking with various stations across the
country. Was consistantly one of the louder stations to whoever
on that freq.. Some were in FLA, some out west, etc.. And I was
just running 90-100w from my 706. I blame it all on the
salty ground and seawater... If that 14 ft antenna did that, just
imagine what my full size GP "should" have done at that location.
Dunno...I think it's all in the ground quality and radials.. Can't
really
explain it any other way.
MK

west wrote:
Anyone have experience with GAP Antennas?

Here is a link to comments on Gap antennas, found on New Jersey QRP
Club's web site :

http://www.njqrp.org/data/gap.html

I personally have no experience with gap antennas.....Your milage may
vary.

Rich k2cpe