Re: SSB - Electronic SP-23 Preamp

Anthony Coldman

Many thanks to all that responded, I now have the circuit for the MK2 that I needed.


Regards Anthony


From: <> On Behalf Of Pete - GM4BYF via
Sent: 11 January 2021 19:17
Subject: Re: [UKMicrowaves] SSB - Electronic SP-23 Preamp


Just seen your message. I have a circuit diagram somewhere, having repaired mine several times. One thing to notice is that the coaxial relays have insufficient isolation on their own, so the input circuit has an additional isolation relay to earth it when on transmit. I also found that a delay of 0.3s was necessary to protect the output of the preamp and allow time for the relays to change over. Get back to me for more detailed information if required.


On 10/01/21 18:49, Anthony Coldman via wrote:

I have a SP23MKII mats head preamp, its not working.


I wonder if anyone has a circuit for it with the component value, I suspect one of the 2 Gas Fet, but unsure on what they are, they seem to be the same possible MGF1302 but not 100% sure.


Does anyone have any information that may help. Its quite an old unit so is there a better replacement device available now?


Regards Anthony G7LRQ

vry 73

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