There is always interaction when mounting separate antennas on the same
mast. Often it effects F/B and SWR more than gain and the only way to
know for sure if this is acceptable is to model the system. I like to put
more than 14% of the mast inside the tower.
John KK9A
To: "n8gls@arrl.net" <n8gls@arrl.net>
Subject: Re: [TowerTalk] HF-VHF-VHF Stacked Yagi's on Single Mast
From: Stan Stockton <wa5rtg@gmail.com>
Date: Sat, 28 Dec 2013 04:54:26 -0600
Brad,
There may be a misunderstanding. You are talking about installing a few
antennas on a mast.
When you refer to capture area(s) and recommended stacking distances it
sounds
like you are looking at some information by some manufacturer on what they
recommend for stacking two or more identical antennas to be fed in phase. Of
course those are entirely different things.
What you won't find from many manufacturers is how a particular antenna is
affected by another particular antenna placed a certain distance apart.
There
are too many combinations and variables. I can tell you is that it is
sometimes a real eye opener to see the resulting interaction and
degradation of
performance, after taking the time to properly model antennas in proximity to
each other.
It looks like 2m is important to you since that is by far the longest boom
you
have. The question is whether the 6m antenna will dramatically affect the 2m
antenna performance. You mentioned the longest element on the 6m antenna
being
5 feet. That sounds like a quarter wave on 6m. Surely it is about 9-10 feet
instead?
73...Stan, K5GO
Cycle 24 Antenna Products LLC
On Dec 27, 2013, at 11:32 PM, "N8GLS" <n8gls@arrl.net> wrote:
> Group,
>
> I have a Hygain HG-54HD Crank-Up Tower which had a Hygain TH5MK2 HF
tri-band
> Beam and a Cushcraft 17B2 2m Boomer all on 8 Ft of mast (10 Ft total with 2
> Ft inside the tower). I?m adding an M² 6m Yagi, changing the TH5MK2 beam
for
> a Cushcraft X7 (w/40m add-on kit) and keeping the Cushcraft 17B2 2m Boomer.
> All to be on 12 Ft of new 1026 DOM Mast (14 Ft total with 2Ft inside the
> tower). The stack will be as follows, from bottom to top;
>
> At 2 Ft from top of tower---Cushcraft X7 (HF 40m-20m-15m-10m), 18 Ft
boom, 6
> elements, longest element 40 Ft, 9.9 Sq Ft wind area.
> At 5 Ft above the X7---Cushcraft 17B2 (2m) Boomer, 31 Ft boom, 17
elements,
> longest element 3.5 Ft, 3.9 Sq Ft wind area.
> At 5 Ft above the 17B2---M² 6M5X (6m), 18 Ft boom, 5 elements, longest
> element 5 Ft, 2.2 Sq Ft wind area.
>
> At the end of the day, I have 12 Ft of mast to stack the above mix of
beams.
> The spacing above is in order of wind surface area, which is my main
> concern. I have looked at capture area(s), recommended stacking distances,
> and I end up needing a mast length that is not feasible for the tower. So,
> does anyone have a better stacking arrangement than the above ???
>
> This project started out as just taking down the old tower and painting
> it?..then after seeing it?s not going to be easy to drop that thing without
> some kind of raising fixture I bought a new US Tower raising fixture and
> re-vamped it to fit the HyGain base, bought the new 6m yagi, then the
> Cushcraft X7, all new coax and rotor cable, new mast, and now I decided to
> have the tower re-hot dip galvanized instead of painting it (cant paint in
> winter)??..and of course it?s December, the end of December actually, in
> northeast Ohio, need I say more ?? Oh ya, and I?d like to get this done
> before the VHF contest in a few weeks?.Ha?.
>
> Thanks for any comments on the stacking?..my XYL is already giving
plenty of
> commentary on all the other?.
>
> 73 de Brad, N8GLS
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