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Author Topic: pair of Hex Beams vertically stacked  (Read 2751 times)
KU7I
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Posts: 122




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« on: January 27, 2013, 10:16:06 PM »

Has anyone vertically stacked a pair of 5 band hex beams? Feedback? Thanks.

Lane Ku7i/JH1JCM
Forward Deployed
US Naval Hospital
Emergency Department
Yokosuka Japan
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K3VAT
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Posts: 730




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« Reply #1 on: January 28, 2013, 02:24:53 AM »

Has anyone vertically stacked a pair of 5 band hex beams? Feedback? Thanks.

Lane Ku7i/JH1JCM

I have not vertically stacked a HexBeam Antenna, but plenty of yagi arrays.

First, vertically stacking, while not exclusively done, is mostly relegated to monobander antennas.  This is because the 2nd antenna is tuned to the 1st to take advantage of the reinforcing amplitudes generated by each antenna.  The distance between them is primarily determined by which band you select and secondarily to the the antenna's gain figures.  To produce the additional gain (a maximum of ~ 3db) requires a specific RF relationship between the two antennas.  For example two M-Square 4 element 20M yagis have a stacking distance around 56 feet; other M-Squared 4 element yagis have significantly different stacking distances based upon their frequency of operation.

Moving the stacking distance a few feet either side of the recommended stacking distance will not substantially hurt their performance; but, if you stacked those 20M yagis (cited above) at 15' apart, they would not work properly and would actually perform worst than a single yagi.

I've read about a few operators who have stacked triband yagis (10M, 15M, and 20M) at a distance apart based on 15M operation and they have reported "very good" performance on 15M and "decent" performance on 10M and 20M.  IMHO, I don't think that you'd see this when using a HexBeam.

Perhaps G3TXQ will chime in on this ... he's much more familiar with HexBeams than most of us (especially me - hi).

GL, 73, Rich, K3VAT
« Last Edit: January 28, 2013, 02:39:22 AM by K3VAT » Logged
W4OP
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« Reply #2 on: January 28, 2013, 06:07:31 AM »

How do you plan on accomplishing the mechanical stacking? I don't own a Hexbeam but isn't the center support an integral part of the antenna feed system - i.e. not just a passive tube?

Dale W4OP
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KA7NIQ
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« Reply #3 on: January 30, 2013, 07:59:14 AM »

Lane, what Rich said is correct. Steve Hunt, G3TXQ, is the go to guy for all things Hex Beam.

I have spoke to several Hams over the years who have used stacks of Triband Yagi's, with good results.
I don't know about the Hex beam. Maybe you will have to go out vertically from the tower, and stack them side by side ?


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G3TXQ
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« Reply #4 on: January 31, 2013, 11:38:35 AM »

I doubt there's anything about the hexbeam electrically that would make stacking two of them any different from stacking other parasitic beams; but as has been mentioned, the mechanical problems will be more challenging  Wink

Steve G3TXQ
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N3OX
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« Reply #5 on: January 31, 2013, 11:51:55 AM »

I doubt there's anything about the hexbeam electrically that would make stacking two of them any different from stacking other parasitic beams

I don't know about Hexbeams but whenever I've modeled it, stacking seems to really mess up Moxons. I haven't sought a retuning solution but it seems to really reduce the F/B.

Might be worth checking for the Hex too.

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
G3TXQ
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« Reply #6 on: January 31, 2013, 12:13:33 PM »

Dan,

When modelling stacked hexbeams you can get a whole range of results, depending on their spacing and height above ground.

Stacking a 20m pair at 35ft/45ft gives me a F/B that is 3dB better than a single beam at 35ft or 45ft; equally I can find spacings and heights where the composite F/B is worse!

One question would be: what is the OP hoping to achieve by the stacking, and what heights/spacings are possible?

73,
Steve G3TXQ
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