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Marconi 2022E RF signal generator repair and refurb

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Fraser:
You may find this page helpful…

https://ea4eoz.blogspot.com/2017/09/repairing-om345-hybrid-module.html

Do remember that the OM345 is a 75 Ohm input and Output impedance and the MAR series MMIC’s are 50 Ohms.

Fraser

bd139:
Yeah have been through that already. I did a calculation on 75 ohm loss and VSWR and it’s trivial at 50 ohms. It’s actually better than the original OM345 input VSWR quoted at 1:2.0

The gain, noise figure are slightly better. Not sure about OIP3. I’ve seen that quoted but no data to back it up. Doing feedback amp calculations against transistor circuit with same topology I couldn’t get better than 20dB which is about as good as the MAR-7SM+.

RF isn’t an exact science or magic :)

djsb:
I have one of these as well. Are you going to share your PCB files or the link to where you're selling any PCBs? I'd also be interested in any webpage/blog with additional info you may create. Thanks.

bd139:
I will write up and share everything once I'm sure it's all tested and working :-+

Edit: just ordered enough parts to build 11x replacement OM345 modules. I'll replace my broken ones, keep some in reserve for to replace the rest of mine when they blow up and stuff the rest on ebay as kits. I can get 30x PCBs for the same as 5x so will over order and sell the remaining PCBs too. Will be sold at cost. Don't need the profit!

Edit 2: perhaps I should lose the Ferengi avatar  :-DD

bd139:
Meant to post this. RF board photo:

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