[Heathkit] Amp Keying Interface?

[Bob McGraw - K4TAX]

Had one of these E. F. Johnson style T/R switches.  This was in about 1960. 
It was found to generate a fair amount of TVI due to the cut-off of the tube 
and when the tube failed (and it did) it dumped about 75 watts of RF into 
the front-end of the receiver.  The receiver really got deaf and eventually 
issued forth a bit of stinky smoke.  I guess the antenna coil in the 
receiver wasn't rated to handle 75 watts or so.

So back to the old DPDT knife switch to do the T/R switching.

73
Bob, K4TAX


----- Original Message ----- 
From: "Peter Markavage" <manualman at juno.com>
To: <heathkit at mailman.qth.net>
Sent: Tuesday, July 31, 2007 3:41 PM
Subject: Re: [Heathkit] Amp Keying Interface?


> You said: "Johnson-style tube tr relays "
> There's no relays in this thing. The antenna is always connected to the
> transmitter. The receiver line is capacitor coupled to this connection
> through a tube. RF Voltage cuts the tube off "preventing" RF from getting
> into the receiver.
>
> Solid-state switching has made great advances over the last 30 years for
> switching large amounts of RF currents. You might want to look into some
> of the new solid-state linears to see how they handle switching large RF
> currents.
>
> Pete, wa2cwa
>
> On Tue, 31 Jul 2007 16:23:55 -0400 <eugene at hertzmail.com> writes:
>> This is a very interesting thread. I have often wondered how to best
>> make a silent TR relay.  I have a standard dow 115vac relay in my
>> station with some aux contacts for muting that makes a real racket!
>> I
>> have always seen the Johnson-style tube tr relays ($$) , but this
>> thread
>> got me to wondering if anyone made a solid state TR relay that can
>> handle 100W? (I mean one for <$50!)
>>
>> Eugene, w2hx
>>
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