[Johnson] T/R relay

Bill Cromwell wrcromwell at gmail.com
Wed Jul 10 23:26:42 EDT 2013


On 07/10/2013 11:00 PM, Charles Ring wrote:
> 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
Hi Charles,

My Johnson Ranger has an issue with a reduced but still present plate 
current flowing with the key up. Using the Johnson T-R switch I can hear 
the "diode noise" in the receiver. Right now I suspect a wiring change 
sometime in the past or a defective part allowing that plate current. I 
have been piecemeal reworking/refurbing the Ranger. The manual says 
there should be no plate current with the key up in the CW mode but 
there is. Up to me to find out why. I am using the open frame relay with 
the Ranger until I resolve that issue - and no QSK.

Is your TX final amp cutoff with the key up? One possible source of your 
trouble.

73,

Bill  KU8H


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