Topband: Protecting an Array Solutions K9AY Loop from Transmitted RF

[K4SAV]

It's likely you won't need any protection from the transmitter 
(lightning protection may be another story).  To verify this you can 
either use an oscilloscope on the output of the K9AY or just build a 
diode / cap detector and use a voltmeter..  Then ramp up the power to 
see how much voltage is picked up.  I was surprised when I did this.  
None of my receiving antennas picked up enough signal to worry about.

Check the pickup on all frequencies you operate.  The gain of a K9AY is 
much higher on higher frequencies even though the pattern is very poor 
on higher frequencies.   It's likely that on higher frequencies there 
will be more voltage across the K9AY terminating resistor than at the 
output of the antenna.

Simulation shows no problem at 60 ft separation on any frequency but 
check it to be sure.

If you decide to use a limiter, make sure there are no AM stations close 
enough to forward bias the limiter (even by the smallest amount).  If 
that happens all kinds of intermod products will show up on receive.

Jerry, K4SAV