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PIN Diode TR Switching



There was some talk earlier about protecting the preamp.  Searching for TR
circuits, I came across the following PIN diode method used by SM5BSZ, Leif
Åsbrink for high-power 2M EME work:

http://ham.te.hik.se/homepage/sm5bsz/pindiode.htm

Looks useful.  Thought I'd share the data.

It might be a good idea to monitor the current in the diode control circuit
to ensure that it isn't broken.  A broken control wire probably means a
toasted preamp.  Better yet, a relay coil (or opto-isolator) could be put in
series with the control line down in the shack and used to key the
transmitter only after the steering diodes were drawing current, helping
ensure that the preamp was protected.  I need to come up with 24V for some
relays that I want to use, anyway, so the +/- 12V control shouldn't be that
hard to make.

73' Dan, KB4L


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