Topband: isolation transformer(s) in RX antenna feedlines (?)

[Herbert Schoenbohm]

Pete.  Here I used RG6 crammed with 10 turns on two 3" toroid on each 
side of a ground block for every cable.  The common point ground block 
is about 10 feet from the shack and consists of the over the counter 
cable TV RG6  ground appliance.  I don't know how much common mode 
rejection i get from this and some Beverage gurus say the toroids must 
be placed right at the antenna but there is already a balun there to 
match the Beverages which essentially isolates the RG6 shield from the 
antenna feed at that point.  My idea was to try and isolate the many 
Beverages fees before they enter the shack.  some also recommend a 1:1 
toroid shield breaker at the shack which is easy to make with a couple 
of turns on a binocular core that shows good performance on 160.  I 
believe this is the FT-243 core but not sure.



Herb, KV4FZ
On 11/28/2014 5:51 PM, Pete Smith N4ZR wrote:
> I ran across a sketchy reference to this idea, described as a way to 
> block common mode signals from making it into the shack by cutting off 
> the paths from the coax shield to the RX input.  Is there anything to 
> the idea?
>