Topband: coax loops - the age old question...

[Missouri Guy]

Pete,

> I would like to be the thousandth who asks the same old question - 
> do, in
> your experience, small coax loops work?

Yes, they DO work.  How well they work compared to other RX
antennas is another story.  In my experience, a 5ft loop
is adequate.  
> 
> I must admit that I fail to see any 
> real
> improvement in S/N compared to my TX antenna.....

> a) disconnecting the TX antenna (which is in proximity of the loop) 
> does not
> determine any change in noise on the loop, and....

Your transmit antenna might be coupling noise into the loop.
Place the loop plane at a right angle to your transmit (vertical?)
antenna.  You can finely adjust the placement of
the loop by connecting a very low power oscillator (at high noon!)
to your transmit vertical, then listen for a null in the signal
received by the loop as you (or a helper) rotate the loop. 
 
> b) I do not use a preamp (I am almost certain that that would not 
> improve
> the S/N...).

You should use a preamp, preferably with a BCB filter and/or some
tuning at its input.  15db gain is probably adequate.

73,
Charlie, N0TT