[Milsurplus] TR switches

[mac]

My experience with a commercial vacuum tube TR switch (Johnson as I  
recall) was that  any strong BC station operating nearby would result  
in a multitude of annoying  intermod products spewing out of  the unit.

Dennis D. W7QHO
Glendale, CA

*******************
On Feb 4, 2011, at 1:44 PM, Bill Cromwell wrote:

> Pete Williams asked:
>
>
> I'd appreciate info/directions to building a useful TR switch for HF  
> and
> capable of handling 500 or so watts. I have relays but not happy with
> the
> lack of fail safe facilities--- having experienced the RF coil on a
> R-390A
> smoking and not good for its health as result of relay hanging up in  
> the
> receive  position.
>
> The ARRL  H/B 1985 edition has some examples  chapter 19-8 and am
> attracted
> to the version using the mosfet,  but wonder if there  are better/ 
> later
> developments .
>
> Your experiences appreciated .
>
> Pete VK3IZ
>
> Hi Pete,
>
> I built and used that exact electronic T/R switch in a homebrew amp.  
> I'm
> a QRP enthusiast so you will have to understand that a 90 watt amp  
> to me
> is QRO. That design uses a section of coax as the coupling cap into  
> the
> switch. I used RG-58. For your power levels you will need large  
> diameter
> coax. That T/R switch is intended to connect on the final amp side of
> the output network so as to not transmit harmonics. That's exactly the
> way I used it. I powered mine from a 9 volt battery and I never, ever
> had any trouble with the rig. My cheap and nasty television located
> about ten feet from the transmitter never suffered any TVI while I  
> used
> an end fed wire antenna.
>
> Good luck with your project. Please let us (at least me) know how it
> goes for you. By the way..I still have the T/R switch in it's shielded
> compartment awaiting use in a new amp.
>
> 73,
>
> Bill  KU8H
>
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