Topband: remotely-controlled Beverage termination

[Tom Rauch]

> Dave (W0FLS) said "I have experimented with changes in termination values
> and have never found it to be a very critical issue based on actual
> measured empirical performance."  The difference between my observations
> and Dave's may be that the max/min frequency ratio on 160 is only 1.1
> (2000/1800) versus a ratio of 3.2 for AM BCB (1700/530).
> 
> Over small changes in frequency, optimum terminating resistance doesn't
> change much, at least on a given day.  

Your applications are totally different also.

You are trying to null a signal station causing QRM, while Dave is 
trying to establish high S/N without regard to depth of a null in one 
specific direction.

I agree with both of you. If I wanted to null a particular offending 
station and I didn't have two antennas to phase, I'd use a variable 
termination. But since I mainly want to dig weak signals out of 
noise that arrives from many azimuthial and elevation points, 
moving the null around won't help me in the least.

Unless you have noise (including QRM, which is also "noise") from 
one dominant source, adjusting the termination to some point other 
than minimum for standing waves on the antenna is an exercise in 
futility. My Beverages remain well terminated over a frequency 
range of at least 5:1, that's as far as I have checked them. No 
reason to adjust then. The reactance changes, but there are no 
light variable reactances that I am aware of.

73, Tom W8JI
w8ji@contesting.com


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