[Premium-Rx] Suggestion for T-R Switching

[Gary Geissinger]

Gentlemen,

I have been reading the email chain concerning ways to safely T-R switch
high value receivers.  There have been some excellent suggestions.

In addition to the previous recommendations, I have placed an RF fuse in
series with the receiver input.  The idea here is that after you have done
everyting else, this gives you one last shot at saving the receiver.  Fair
Radio Sales (and others) sell the inline N connector to N connector RF fuses
that came with the URM-25 and some other signal generators.  They were
designed to protect the signal generator when testing transceivers.  I have
found 1/16th amp ultra-fast instrument fuses that I use in the housing.  It
may still be possible to find 1/100th amp instrument fuses; I just haven't
looked.

While this fuse will still pass some serious power (+22 dBm), it has saved
my receiver twice when my T-R relay hung up!  The last time this happened I
placed a pair of Shottky diodes (one each direction) across the input of the
receiver to ground to help pop the fuses.  While the diodes can cause some
serious receive problems in a strong signal environment, saving the receiver
was my first priority.

Regards,

Gary       
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