In researching the subject during the past year, I've looked at the
relay
circuits of a number of commercial amplifiers. Most seem to treat T/R
switching pretty cavaliearly, without adequate protection for the
relays. In
my own design (the circuit mounts on a 3"x5" PCB), I've tried to
prevent any
situation that can damage the contacts. This involves several
precautions:
(1) sequencing the amp so the output relay, bias switch, and input relay
operate sequentially in that order, after allowing for the relay closing
times and contact bounce. (2) Having an RF "lockout" sensor that
prevents
the amplifier switching sequence from beginning if RF is present on the
input line. (3) Having an RF "lockon" sensor that keeps the relays
closed so
long as RF is present. My new amplifier completes its T/R switching
in 4 mS,
which is suitable for QSK speeds up to about 60 wpm, far beyond it's
builder's capabilities.
73,
Jim W8ZR
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1432 / Virus Database: 3222/6324 - Release Date: 11/10/13