CQ-Contest
[Top] [All Lists]

Re: [TowerTalk] Coax Stubs for SO2R

To: <towertalk@contesting.com>, <cq-contest@contesting.com>
Subject: Re: [TowerTalk] Coax Stubs for SO2R
From: "Mike Smith VE9AA" <ve9aa@nbnet.nb.ca>
Date: Tue, 8 Sep 2015 18:14:26 -0300
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Thanks for the many replies so far.  So today after I got home from work I 
tried just running radio A @ about 1w on 7.000MHZ and saw S9 on 20m and s1 on 
10m.

No change switching stub in or out, so I took Jim’s(K9YC) suggestion and moved 
the stub farther away from the transceiver.  I made up 3 random length patch 
cables and so have the stub roughly either:

10-12’, 15’-17, 20’-22, 25’-27 away from the transmitter (Radio A). (rough 
guesstimates)  ( a 1/4wl, accounting for VF would be in the 23’-27’ range)

No perceptible change whatsoever at any point in the line no matter where I put 
the stub.  Just the slightest SWR change when I put it in line.  Almost cannot 
detect it.

 

I am going nuts.

 

It’s either something in the shack or something outside rectifying (I guess?)  
but these are pretty low power levels. (usually 100w, but also at 1w !)

 

Radio A (transmitter in the scenario) is hooked to an amp (not turned on in 
close to a year), an antenna switch, a tuner/wattmeter (used on straightthrough 
function only, just for it’s wattmeter/SWR function.)

Radio B (receiver in this scenario) is hooked to its own power supply and coax 
straight outside to a multiband dipole some 100’ from the Radio’s A’s various 
antennas. No SWR meters, switches or anything.

 

They share a 4” hole in the wall in the garage where they exit to the outside, 
where the RG8 or LMR400 coax;’s could be close to one another.

They share 120VAC  in the shack (but different power supplies)

 

I have two additional (perhaps important?) questions.  Should any of these 
harmonics between any bands sound pure and “clean”, like a real CW signal?  
Mine all sound low/muffly, wide, growly, like they have buzzing/humming AC 
riding on top of them.

 

Additionally, the AA-230pro’s manual says to make the 1/4WL stub with the end 
of the coax OPEN.  . . . .but then for the purposes of these tests, I am using 
the stubs shorted.

 

Maybe I have a ground loop somewhere and there is feedback or an isolation 
problem on the shacks’s 120VAC line?

 

Mike

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>