[TowerTalk] Tuning coax stubs w/ shack test equipment

[km1h@juno.com]

On Tue, 30 Mar 1999 10:48:03 -0800 "Mason, Ken R" <ken.r.mason@intel.com>
writes:
>
>Hello Fellow Hams,
>
>I had tried to work with stubs to prevent intermod during a VHF 
>contest.
>Station consisted of 1500 watts on 6M and 1500 watts on 2M. Of course 
>the 6M
>station was killing the 2M receiver. I made a 19 inch approx. 1/2 
>inch
>hard-line shorted stub and put it on the 2M radio using a tee 
>connector.
>
>The results were poor. The 2M radio worked fine but the 6M signal 
>still got
>in. Checking it with the mfj 259 showed it was super wide. using a 
>tee
>connector with a dummy load and the shorted stub showed about 40 ohms 
>on 6M
>using the mfj 259.
>
>Is this to be expected? I need to remove the intermod signals on my 2M 
>and
>432 radios. Any ideas for my single tower contest station? ( no, not 
>another
>tower)

Given the overload , IMD and phase noise performance of most VHF
multimodes and the latest 160M to light allbanders it may be an imposible
task.
It would be best to start at low power and work the level up to the point
that problems are evident. Then try and do interference reduction in
incremental steps.

I use a ICE LP at the output of my 6M amp and an old Henry 3002 LP on the
2M amp.
Also use a Waters 373-6 ( antique)  at the input for 6M and a DCI filter
on 2M; both of the input filters are bandpass types. 

Antennas are on different towers about 50' apart but there is absolutely
no interference at the legal limit.
Xcvrs for both bands are TS-830S's with transverters.

There are also 150MHZ band paging transmitters on another tower on my
property plus a neighbor with a ton of VHF/UHF 2 way. Interference is non
existent.

GL  Carl  KM1H


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