[Johnson] T/R relay

[Charles Ring]

I have used the 250-39 Johnson T/R switch since 1967. I've had 3 of them 
and the power transformer on two of those have failed. Since returning 
to the air a year ago I've been using one with my Globe King 500A and 
Drake R-4C.  It works, but unlike long ago, I can't get full QSK. The 
receiver is being badly desensed. I don't remember if it did better then 
with the R-4C or if that was only with the 2-C and the R-4B, both of 
which are waiting for repairs. I am interested in changing to either a 
fast relay or a PIN diode switch. I seldom do faster than 25WPM.

73 de W3NU



On 7/10/2013 1808, Carl wrote:
> Most all commercial ham amps in the 1000-1500W range use open frame 
> DPDT or 3PDT relays in the 10-13A contact range.
>
> Since the Johnson Desk is capable of 3000W PEP on AM I would suggest a 
> relay with 15-20A contacts and use a capacitor to compensate for the 
> XL bump on 10/15M.
>
> The readily available vacuum relay such as the RJ-1A or equivalent is 
> SPDT so you will either need 2 of them or a small relay on the input 
> that is fast enough. My amp uses a regular DPDT DIP relay with the 
> poles in parallel and a sequencer that allows 50 wpm QSK without hot 
> switching but I stick to 20-30 wpm of VOX CW and SSB and it has held 
> up since 1986.
>
> Perhaps the simplest approach is the Johnson 250-39 Electronis T/R 
> switch which is rated to 4000W PEP. I havent run mine beyond 2000W PEP 
> on AM and its none the worse for wear.
>
> Carl
> KM1H
>