[TowerTalk] Stubs and Reactances in parallel

[Jim Brown]

On 6/24/2020 11:20 AM, Steve London wrote:
> Is there another solution I am overlooking ?

Hi Steve,

Yes. Feed the two antennas separately. Use a stub in the 80M feedline as 
detailed here to kill the harmonic of 80 on 40.
http://k9yc.com/LocatingStubs.pdf and
http://k9yc.com/StubPlacement.pdf

The same stub, properly placed, will apply a short at the feedpoint of 
the 80M antenna, which should kill the interaction. I learned this a few 
years ago doing an NEC model of our contesting trailer's antenna system 
k9yc.com/7QP.pdf  I work with N0AX on the Handbook and Antenna Book, and 
when I told him what I'd learned he nodded his head yes, he'd known 
about that for years. The ancients keep stealing our inventions. :)

Also, remember that VF varies enough with frequency that stubs must be 
measured and tweaked to length at the frequency where you want them to 
be a short. The variation is enough to move their resonance to a 
different part of the band.

73, Jim K9YC