[Boatanchors] Lysco 600S T/R Switch

[Glen Zook]

An electronic "TR" switch does NOT activate a relay! 
It isolates the receiver antenna circuit from the
transmitter when r.f. causes the tube to "cut off". 
When the r.f. is removed, the tube again conducts and
the signal from the antenna goes through the tube to
the receiver.

A "TR" switch allows full QSK operation.  However,
they are also "famous" for generating harmonics of the
transmitted signal and causing TVI as well as problems
with the FCC.

Glen, K9STH


--- Bill Stewart <bstewart at ipass.net> wrote:

> I have a Lysco 600S that's about ready to put on the
> air. I noticed that it has a Lynmar Engineers Inc
> Trans-Receive Switch type TRS-1 which either came
> with it or was added later. The T/R switch uses a
> 6AH6 sharp cutoff RF pentode tube. There is a
> feed-thru with a mica cap which goes to the final
> var. cap. There is a phono jack on the top which I
> measured anywhere from around 5-8 Volts AC...this
> may vary with the RF output. I connected a 6.3 VAC
> relay to the phono jack but it didn't pull in but
> the switch output voltage did drop with the relay
> coil load (it still had close to 6VAC)
> 
> My first question is does anyone know anything about
> this T/R switch? The switch is built in a small
> mini-type box. Three wires connect below the xmtr
> chassis for B+, fil. and gnd. The phono jack is
> connected to a coil wound similar to a IF coil.
> I guess that it senses RF thru the mica cap and this
> cuts the tube on and off for break-in keying.
> 
> My other question is has anyone rigged up a T/R
> switch for this xmtr? I don't like break-in keying
> on my boatanchors. Even if I can get this T/R switch
> to work I'm not sure I would want to use it. The
> xmtr B+ stays on all the time. The keying selector
> switch (S4) doesn't have a spare pole I can use for
> switching. I am considering moving the line from the
> modulator 6V6 cathode from S4D to the spare S4C
> connection and grounding it thru the key if I want
> to use the modulator (probably a rare occurrence
> considering the low power). Then S4D will be freed
> up to gnd a 6.3vac relay. I would like to keep any
> modifications to a minimum. Anyone have any thoughts
> on this? Are there any Lysco users out there?? Many
> thanks for any comments......73 de Bill K4JYS


=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco


		
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