[Elecraft] Prevent Snow/Dirt Static damage to KPA100 after upgrade
Ron D'Eau Claire
ron at cobi.biz
Sat Oct 23 22:35:05 EDT 2010
One easy way to tell if an RFC is good across the antenna terminals is to
check the SWR before and after installing it on *each* band.
If the SWR doesn't change, the choke is good to go. What you're checking is
for adequate reactance at the lowest frequency and no series resonances on
other frequencies.
I'd play it safe and check at frequencies near the bottom and top of each of
the bands - at least those more than 100 kHz or so wide and especially the
higher frequency bands.
The old RFC10 was designed for that duty, of course, but it was used from
1.8 to 30 MHz. I'd check carefully for sign of it moving the SWR if someone
wants to use it on a K3 at 6 meters.
If a choke isn't handy, I'd not worry much about having a d-c short over a
50K resistor. The intent is to bleed off the static charge as it accumulates
and a 50K resistor will do that very well. The antenna presents a limited
capacitance and the charge accumulates relatively slowly. It doesn't take
much of a path to ground to pass enough current to keep the d-c charge near
zero.
Ron AC7AC
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