[TowerTalk] Fwd: Mast and stacking question

[JC_Smith@designlink.com]

KB3X writes:

===== snip =====
My last question has to do with the interaction between the antennas.  I have
noticed there has been a thread or two on this subject lately.  Currently, I 
have the KT-34XA with the Cushcraft A-3WS 6 feet above it.  A KLM 40M-1
rotary 
dipole is 7 feet above that with the element parallel with the booms of the 
other two antennas.  The question is what interaction might I expect if I 
change the 40M-1 to a Cushcraft 40-2CD?  What would be the best spacing, and 
placement, of these three to minimize any problems?  The current towertalk 
thread seems to indicate that I will see interaction between the WARC antenna
and the 40-2CD on 17 meters.  However, I haven't found anything so far to 
indicate how I can reduce or eliminate it.  Again, any thoughts here?
===== snip =====

Hi Scott,

I was part of that thread as one combination I am considering for my new tower
is a Mosley TW-33-XL (WARC tribander) with a Cushcraft "Shorty Forty" above
that.  (My 10-15-20 is on another tower.)  I believe the problem relates
specifically to the Cushcraft 40 as it is quite a bit smaller than other 40
meter Yagis and aparently has a resonance on 18.1 MHz.  Your KLM should be
quite different.  I think you will have more to worry about between your KT-34
on 15 and whatever you put up for 40.  I think I'd stay with the 90 degree
rotation split you are using now.

I haven't tried any of these combinations yet, so this is just speculation. 
Hopefully someone with some actual experience will come along and enlighten us
both.  As it stands now, I'm abandoning the Shorty 40 idea and looking at
larger units, but now I may have to put the 40 on the bottom for structural
reasons.

73 - JC,k0hps@amsat.org





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