Topband: Isolating a TX antenna

[n4is]

Mike


>How much noise should I expect, is 2 S Units reasonable, 
>and what other methods should I consider to reduce, and hopefully 
>eliminate this problem?  I'm ready for winter.


You did it right, the float part of the inverted L become 1/4 element, and
it does not reradiate, before with the ground it was a resonant element. 

The noise reduction depends on the direction of the receiver array null,
front back, and the main noise sources like power line noise. My RX antenna
is 50ft from my 1/4 full size vertical, and it is common to see 10 to 15 db
increase in noise when I remove the detuning circuit on the TX antenna. 2 S
units reduction is right in the money. I 'm using a vacuum relay to float
the cage on my TX antenna; it is a Unipole with a cage. 

Another thing very important is to choke the RX line to reduce common mode
noise. Take care of the input of the preamps; one small choke right at the
input of the preamp with a short length of cable can avoid noise to get into
it.

Regards
JCarlos
N4IS