Topband: "Is your feedline also an antenna?"]]

[Andy Ikin]

 "Unfortunately this doesn't apply at all to HF receiving. It
only means something at 60 Hz, where it affects video.

Tom, For the purpose of dealing with signal ingress, would not the Faraday
Shield cure work on 1.8Khz as it does at 60 hz?

Herb Schoenbohm, KV4FZ"

Herb, Some years ago I investigated a poor s/n for a 60kHz radio clock 
system in two underground bunkers. Each system used 250m run of RG58c to a 
active ferrite rod antennas. In both cases the poor s/n was caused by noise 
induced on the feeder screen.  Three ideas were tried out! 1) a Faraday 
screen Tri-ax. 2) 100 Ohm Balanced screened Twin-ax plus Baluns. 3) 10mH 
common mode choke; 30 turns RG58c wound on 2 large ferrite rings.  The 
Tri-ax idea was a total failure. The Twin-ax and the choke, both provided a 
cure.

Here at my QTH I have 4 RG58c feeders each 40m running out to my antennas. 
With all the feeders dis-connected I still have S9 +10 on 198kHz and S7 on 
693kHz ( 500kW Tx 80km at Droitwich ). If I isolate the power line L+N with 
good quality mains filter and use a separate ground rod with the Rx,198kHz 
drops to S2 and 693kHz drops to S1. A further reduction in signal ingress is 
afforded by fitting an 1:1 isolation tranformer at the Rx antenna input. 
Hence, one can assume that the overhead power lines are picking up RF and 
this is conducted along the feeder screen!!!
Fitting the mains filter and the isolation transformer also signifficanlty 
reduces power line noise radiating from the antenna feeder to the antenna.

73s

Andrew Ikin
Wellbrook Communications





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