Hi, Mike
I remember the guy that you are referring to, but it's been so many years
that I don't remember his last name tither. He published a book via either
ARRL or CQ mag.
A collinear 1/2 wave over a 1/4 wave GP has certainly been done and used
commercially at VHF. The "skirt" can also be replaced with a shorted 1/4
wave phasing line.
Well, Tom's tower is probably tall enough - but how in heck would we get the
verticals far enough away from the tower??
Charlie, K4OTV
-----Original Message-----
From: Mike Armstrong [mailto:armstrmj@aol.com]
Sent: Friday, September 06, 2013 10:42 PM
To: Charlie Cunningham
Cc: ZR; Shoppa, Tim; <topband@contesting.com>
Subject: Re: Topband: Are stacked verticals feasible?
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 skirt 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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