[NLRS] Another antenna position question!

[W0ZQ@aol.com]

Hi Bill.   Great weather for antenna work, huh.   Regarding placement of 
antennas on the same mast, there is not doubt that the best thing to do is to have 
separate towers for each band.  That would be nice huh.   

When you mount a "stack" of different freq yagis on one mast you need to 
consider windloading, mast loading, maintenance (the top one always breaks first), 
in addition to beam to beam interactions.   Life is often a compromise .... 
someone once told me that engineering is the art of compromise.

Regarding interactions, its usually the higher freq antenna that is affected 
most; for example a 432 yagi may "see" the 2m yagi but the 2m yagi does not 
"see" the 432 yagi.  

I try to keep my 432 antenna away from my 2m antenna.   As such, my "big" 2m 
antenna is on the bottom of my 8' mast, followed by the 222 yagi with the 432 
yagi at the top ... there is about 3.5 to 4' of separation between the three 
antennas with the 432 & 2m the farthest apart.  Just above the 2m antenna I 
have a small H-frame that mounts the 902, 1296, and 2304 loopers .... the booms 
are parallel with the 2m yagi with an actual separation with the 2m beam of 
about 3 feet (about 1.5 ft up and 1.5 feet out (left & right) on the H-frame).   
The 2304 looper is perhaps a foot off the 2m boom in the middle of the 
H-frame.

I've tried mounting my 6m antenna up there too, but I think the small H-frame 
resonates at around 50 MHz because the 6m SWR goes crazy and I cannot adjust 
it down .... so instead it sits on a chimney mount at 25 ft and turned with a 
TV rotator ... yea it doesnt work as good as it would at 50' but remember that 
compromise thing ?

I think that you can stack different band yagis on one mast.   Yes its a 
compromise but yes it will work.   Keep 432 as far as reasonably possible away 
from 2m and keep at least 2' separation between all bands .. more is better ... 
but this will work.   Watch  your SWR ... if you can measure your SWR before 
the new antenna is installed and then again after its installed and see no 
significant change, chances are good that the interaction is minor.  Again, its 
almost always the higher freq antenna that see's the lower freq antenna.   

Happy antenna building.

73, Jon
W0ZQ


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---