Tongue in cheek here, how bout out to the antenna?
Gary...wa6fgi
On 3/3/2018 4:16 PM, Joe wrote:
Hi Jim,
You ask
"What is the RF path for antenna switching in the SB220?"
Not sure what you are meaning to ask here. Please clarify.
Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 3/3/2018 4:40 PM, Jim Brown wrote:
On 3/3/2018 12:09 PM, Joe wrote:
BUT I may have fixed it by accident. I have been in the process or
bringing an old dead SB-220 back to life, and have put it inplace
this morning, so cabling has changed greatly in the shack. And the
problem may be gone now by just changing out all the cables?
Lots of problems like this are caused by a bad piece of coax, or coax
with a poor shield connection (or no shield connection). Under normal
operation, current on the center conductor returns on the shield, so
the field stays within the coax. When there's no shield connection,
current returns on whatever path Mother Nature finds, and there's a
strong field OUTSIDE the coax. That field radiates, and also
magnetically (inductively) couples to anything around it.
What is the RF path for antenna switching in the SB220? Many unwashed
engineers used the chassis as return rather than running coax. This
creates the same sort of problem inside the amp -- current returns on
the chassis rather than the coax shield, so it produces EM and
magnetic fields. GOOD amp designers use coax for everything in the RF
path.
73, Jim K9YC
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