[CQ-Contest] coax stubs in MS -SO2R

Jerry Flanders jeflanders at comcast.net
Fri Oct 14 10:25:51 EDT 2005

I recommend you measure your RF levels.

When I was setting up my stubs, I made a RF detector with 50 ohm load 
for my multimeter and simply measured the RF voltage on the "other" 
coax when TXing at full power on the first coax. I did this for all 
bands. I reasoned that if the RF voltage was below the level that 
would zap modern SS devices, it wouldn't hurt the "other" rig.

With my antennas well separated and stubs in place, my worst-case was 
around 270 mv. I ran with this level for a long time successfully. I 
now also have filters (found a good deal on a used pair), so I should 
be even better now, though I haven't measured it again.

FYI: I run one dual-resonance 40+15 antenna on one coax on rig 1, 
another dual-resonance 20+10 on a second coax and a separate 80 
dipole on a third on rig 2. Easy to arrange stubs this way without 
any stub switching, and I can run any two adjacent bands together.

My antennas are fixed. You will need multiple measurements as you 
rotate your yagis.

Jerry W4UK

At 04:15 10/14/2005, Marc Wullaert wrote:
>I'm preparing my station for the coming contest season as a MS setup or
>SO2R.I'm coming now to the part
>for the coax stubs to deal with harmonics.This is the antenna setup.
>Tower 1: 24m tower shuntfed for 160m.On top whe have
>10-15-20m tribander KT34XA@ 25m  and a 40m cushcraft 40-2CD @ 29m
>On 80m I have a 1/4 wave elevated vertical hanging from this tower.
>Tower 2 : 18m tower  with a second KT34XA(10-15-20m tribander).And inverted
>vee for 80m.
>I have also one elevated 1/4 vertical for 40m nearby the second tower.
>Spacing between towers is 35m (115 foot)
>On tower 1 is a 8ANT/2RAD homebrew switch controlled by banddecoders.
>Both stations have high power amplifiers.
>What soud be the best configuration of stubs for this setup..Is it ok to
>place the coax stubs on the antenna switch
>at tower1.Is there a possibilty to have one stub or multiple stubs or lumped
>at the same time on the tribander antennas for the
>3 bands?
>Marc ON4MA (OT5G in both CQWW-2005)
>CQ-Contest mailing list
>CQ-Contest at contesting.com

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