Carl and Charlie,
I am not sure it would even be close to practical or even doable, but I
remember seeing an old book on verticals written by a prior Navy Captain, I
believe. He had a very interesting design for what WE would, today, call a
collinear that was 3/4 wave length tall on 20 meters..... it was, in reality
what looked like half of a double-zepp antenna in a vertical orientation. It
intrigued me that it was like a half wave stacked on top of a 1/4 wave worked
against ground (normal radial field). The interesting part was how he used a
"skirt" around the "middle" quarter wavelength portion to produce the the
in-phase relationship with the physically lower 1/4 wave.
You guys may already know the design I am talking about. I saw that book a
long time ago, like back in the late 60's I think..... maybe early 70's. I was
considering trying to find the article or book whenI was looking for a better
vertical for my winlink node on 20 meters..... the one I have been talking
about. However, I tried the 5/8ths first because I knew how to build one
without having to possess any special instructions. It was so successful, that
I completely forgot about the "collinear." On the other hand, this discussion
reminded me of that book and how author "raved", a little anyway, over its
performance. I remember that the height of the finished antenna for 20 meters
was something very close to 50 feet...... and that is not much taller than a
5/8ths..... maybe 7 or 8 feet taller. So on 20 it is very doable and,
supposedly, it has some reasonable gain for the effort. I would like to find
the book because it described a good way to make that all-important s
kirt that got the phase correct between the upper half-wave and the lower
quarter-wave sections. Due to its relatively tall structure, it probably
wouldn't even be "possible" to build one for 160..... at least not by most of
us. It would be interesting to see if it has the same "problem" that Tom was
referring to for the 5/8ths..... "too low" radiation angle. I know it isn't
supposed to have that secondary lobe that a 5/8ths has...... So maybe it would
be an improvement ..... IF it was even possible to build one. That would be
one tall structure on 160.... LOL LOL. Still, for someone needing an omni
antenna with some gain on the higher HF bands, it might be a decent answer.
Never built one, so I really don't know if it really works or not. Although,
as I said, that author was a Navy Captain whose job was designing some of the
shipboard antenna systems, like the NORD and some other odd ducks.... Well,
"odd" to those who don't have to build low loss, low band antennas on
a floating "postage stamp." I know, I know, you might have trouble thinking
of something the size of an Aircraft Carrier being referred to as a floating
postage stamp, but if you have spent any time at sea on a "big deck," you know
exactly what I mean by that statement...... he he he he. I really should
remember his name, darn it..... with all the time I spent on ships at sea
working with his designs, it is really sad (bad?) that I don't remember his
name...... Paul "something?" I'll find out..... lol
Mike AB7ZU
Kuhi no ka lima, hele no ka maka
On Sep 6, 2013, at 19:03, "Charlie Cunningham" <charlie-cunningham@nc.rr.com>
wrote:
> Well, Carl
>
> You just proposed a total height of 3/4 wavelength, it seems. Do you have
> that much height?
>
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of ZR
> Sent: Friday, September 06, 2013 9:26 AM
> To: Shoppa, Tim; topband@contesting.com
> Subject: Re: Topband: Are stacked verticals feasible?
>
> Look at it as 2 ground planes with the lower feed point 1/4 wave above
> ground along with its elevated radials which should make it pretty much
> ground independent according to what has been published on here and
> elsewhere.
>
> The second ground plane would be identical with 1/4 wave spacing from the
> top of the lower antenna or a 1/2 wave between feed points.
>
> Then I would think that the ground conductivity at the reflection point
> would be the only concern as far as efficiency and gain??
>
> If installed as vertical dipoles then there would also have to be additional
> spacing between them.
>
> I would think that at 6-12' spacing from the tower it would minimize
> interaction on 160 or 80?
>
> Does anyone on here have EZNEC and can plot this?
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "Shoppa, Tim" <tshoppa@wmata.com>
> To: "Carl" <km1h@jeremy.mv.com>; <topband@contesting.com>
> Sent: Thursday, September 05, 2013 10:30 PM
> Subject: Re: Topband: Are stacked verticals feasible?
>
>
>> Isn't this a "Vertical dipole"? Two quarter wave radiating elements? And
> tower behind it will be some kind of reflector/director depending on height.
> The radials seem unimportant if thought of this way.
>>
>> Tim N3QE
>> ________________________________________
>> From: Topband [topband-bounces@contesting.com] on behalf of Carl
> [km1h@jeremy.mv.com]
>> Sent: Thursday, September 05, 2013 9:17 AM
>> To: topband
>> Subject: Topband: Are stacked verticals feasible?
>>
>> Assuming that sufficient tower height was available, guy wires are
> insulated
>> or broken up into short non-resonant sections. Tower face is 12 or 18".
>>
>> Start at 1/4 wave up with a 1/4 wave ground plane with radials sloping at
>> about 45 degrees. The vertical wire is 6-12' away from the tower face.
>>
>> Then a 1/4 wave (or 1/8) up install a duplicate.
>>
>> What does EZNEC say about this?
>>
>> With the different spacings?
>>
>> Effect of starting lower and how low before there are ground related
>> problems?
>>
>> Phasing with coax or a LC network?
>>
>> Switching in a delay line to tilt the lobe up a bit?
>>
>> Curiosity got the cat!
>>
>> Carl
>> KM1H
>>
>>
>>
>>
>> _________________
>> Topband Reflector
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>> Topband Reflector
>>
>>
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