> One of the dumbest things I've seen recently from a very good company is
> RF chokes in series with the shield connections on analog and RS232 I/O
> boards for the Elecraft K3.
Shielding and grounding is probably the least known art, as are audio line
source and load impedances.
I had problems with my K3 when I pointed my Yagi's at the house. As a quick
fix, I cut into my mic cable and grounded the shield to a cabinet screw. :-)
Later, I added some adhesive backed copper foil and got rid of the ground
choke. Good thing about Elecraft is they fix bugs fast in production.
ICOM ran an audio (mic) shield and a key paddle shield around inside the
radio, instead of an entrance ground common point to the case. First time
the negative lead comes off the 12V power supply or the negative fuse blows
while a grounded case keyer is plugged in, and it melts the circuit board
foil inside the radio. The same ICOM model in my shop lost the shield on the
mic, because I lost a negative lead to the PS while a signal generator was
connected. Turns out they had a small axial lead shield RF choke, and it
opened up. The power supply negative returned through the safety ground on
the generator to the mic shield.
RF-wise, however, rigs are very good now. They are nonresponsive to RF
ingress into the receiver on power and control jacks, and the output
connectors are all very immune to generating CM RF on cable shields.
My old boatanchors are often like open RF doors to the power mains. Some
even bring so much RF out the front on knobs, they can pull the VFO off
frequency! Things definitely are better.
73 Tom
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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