TopBand: fences

[w8ji.tom]

Adding a choke in series with the HV output works quite well to slow the
rise time down in the fence voltage.

HF energy is greatly attenuated by the combination of shunt distributed
capacitance in the fence and the high series inductance of the 1 mH choke.
Avoid any choke that might be series resonant on 160 meters, but try to
find one that has several thousand ohms Z.

The chokes Ameritron uses in HF PA's at the output of the tank circuits
worked well for me.

The charger I fooled with also coupled a nasty pulse back into the power
mains, so I bypassed the mains to ground using the UL/CSA rated line bypass
style caps. Remember fooling with line connections can get you in trouble,
so if you don't know what you are doing BUY a brute force line filter and
let the supplier share most of the liability if something goes wrong and
the power line gets faulted to the case of the charger. This is a potential
problem because both the pulse from the fence or lighting might damage a
bypass cap, connecting the mains to charger case.   
 
My neighbor was friendly, and let me have the charger for a day. She also
was running the thing on a two wire cord and had it grounded to a PVC pipe.
If anything ever shorted the line to case in the unit, she could have been
history with no grounds on anything. As it was, you could get a whack off
the case when the fence fired. BE SURE you understand what you are doing
before messing with someone else's power line connections!

73 Tom

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