[TowerTalk] Coax STubs for SO2R

[Jim Thomson]

Date: Mon, 7 Sep 2015 19:36:09 -0300
From: "Mike Smith VE9AA" <ve9aa at nbnet.nb.ca>
To: <towertalk at contesting.com>Coax STubs for SO2R


I've seen the K2TR stubs, K1TTT page and have recently bought the FB book by
W2VJN

Today, for a change, I had a little spare time so built 2 stubs, but lets
just concentrate on one.

It was supposed to be for the 40m transmitter.  

I roughed out the length, attached a T and my antenna switch (a la VA2UP
method) (which I'll only use for stubs, trimmed it with my AA-230pro

and when it's inline (parallel to my primary antenna switch) I see no
difference at all on 20m or 15m on my 2nd receiver when the stub is in or
out of line

NONE.  Like, not even a titch ESP hopeful. (hi)

I presume this is a type 1 stub (shorted 1/4WL type, x velocity factor) 

Thinking I had done something wonky, I made another stub from different
coax..same result. Anyone been down this road? Too close to rig?

Interaction from my T and 2nd antenna switch?  Gremlins? Wrong method using
the AA-230 pro maybe?  I am close to that 23' mark. 

de Mike (SO2R hopeful) VE9AA

##  If I have the theory correct, the 40m stub is a 1/4 wave on 40m...and a 1/2 wave stub on 20m. 
It will attenuate I think, just 20m and also 10m..... but not 15M.    The Z at the end of the coax, in the shack,
plays a large part.   Plus is the amp a PI or a PI-L ??   The 1st stub has to be in the correct spot.  A 2nd stub is
usually located a qtr wave further downstream from the 1st stub. 

##  Id almost be inclined to use high powered  band pass filters, one for each band.  Although initial
cost would be  sky high, at least they would also work on RX....and  simplify things. 

Jim  VE7RF