[50mhz] Stacking interaction with 15 & 20 monobanders?

[LANCE COLLISTER]

Hello Tim,

There certainly is the question of interaction between such closely spaced 
antennas...however there is another aspect that is extremely important.  That issue 
is ground gain.  One of the biggest contributors to success with a single yagi is the 
amount of extra ground gain that it is able to develop.  This can make a single yagi 
act like 4 yagis (6 dB extra gain) under the right circumstances.

The right circumstance is generally when the antenna aims out over smooth uncluttered 
terrain, which can reflect the signals cleanly up to the antenna off the ground.  The 
wrong circumstance is generally when an HF beam is mounted below the 6m yagi, so as 
to appear as ground and shield the 6m antenna from the valuable ground gain reflections.

If you are unable to mount the highest frequency (6m) yagi on its own tower, or at 
least on the BOTTOM of the stack, you might want to consider mounting it at right 
angles to the HF beams, so they will appear to be more "invisible".  This was the 
only way that 4F2KWT was able to complete with me on 6m EME with his single yagi:

http://www.bigskyspaces.com/w7gj/4f2kwt.jpg

If you are interested in weak signal DXing and high performance from your antenna, it 
pays to take the time to maximize the ground gain!  GL and VY 73, Lance

N3XX - Tim Heger wrote:
> Looking for opinions on possible interaction if I mount a 6 Mtr yagi between my
> existing 15 and 20 Mtr 5 element monoband yagis on the same mast.  The 15 and 20
> Mtr yagis are 11 ft. apart on the mast, and I would be mounting the 6 Mtr yagi
> midway between them.  So about 5.5 ft. distance to either of the yagis above and
> below.  The 6 Mtr yagi would be 5 elements, on an 18 ft. boom.  Would like another
> element or two, but don't want to add too much more wind load to the mast with the
> additional boom length. I'm afraid the other antennas would be too close, and
> possibly the 6 Mtr yagi wouldn't perform well in this configuration, but trying to
> save on the additional money that would be spent to rotate the antenna with a side
> mount arrangement on the tower. I guess I could just go ahead and put it up there
> and see what happens.  It could always be moved if there is a problem. Or, maybe
> someone has a good low cost solution to antenna rotation with a side mount.  The
> TIC rings are nice, but would be spending about 3 or 4 times more for the rotator
> than was spent for the antenna.
> 
> Thanks - 73, Tim - N3XX Moderator: Ray Brown, KB0STN 
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-- 
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
P.O. Box 73
Frenchtown, MT  59834  USA
QTH: DN27UB
TEL: (406) 626-5728
URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11/6m DXCC #815