[TowerTalk] HF-VHF-VHF Stacked Yagi's on Single Mast

Stan Stockton wa5rtg at gmail.com
Sat Dec 28 08:27:23 EST 2013


Brad,

It was relatively easy to model a fairly large 2m antenna design I had with a small 5 element 6m antenna above it by 5 feet.  In the case of the two antennas I used in free space the degradation in gain was only .4 dB.  The SWR was nearly identical and the front to back was actually about 4 dB better.

73...Stan, K5GO

Sent from my iPad

On Dec 28, 2013, at 4:54 AM, Stan Stockton <wa5rtg at gmail.com> wrote:

> 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 at 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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>> 
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