LF: TRX-switching

["Hans-Albrecht Haffa" <dk8nd@web.de>]

Dear OMs,

kindly I ask You for ideas for a TRX swiching circuit with pin diodes for LF and MF. In the magazine "Funkamateur" 2/2017 an article of Donald Huff, W6JL ist published, using PIN-diodes 1N4007.  A similar publication will find in the internet too from K9EW ("Boat Anchor QSK "). Both authors are using succdessfully rectifier diodes for 50 Hz as PIN Diodes for  switching 1, 8 MHz until 30 MHz.  Pin Diodes have a minimum usable frequency based on reverse recovery time of the diode, usually higher than 1 MHz.  

I need `nt a full  switching circuit, as I have a power output of the vac relais (Jennings dpdt (2 mal um), too slow for qsk) in receive path  of abt -17 dbm in transmit mode, and I wish to a have an output of abt 30 uV (-77dbm) in receive path. A complete blocking of receive path ist not necessary, as I need a bit of TX-sig for having a sidetone in transmit mode. I use a "Line"(...what an old fashioned _expression_  for an not affordable equipment......).  Solving the problem  by muting the receiver, adding a side tone in an audio-postamplifier for the head phone means additional circuitry around about the receiver, what I want to avoid . 

Your proposal? Any ideas welcome.

 

55, Hans-Albrecht

DK 8 ND