Hi,
Omce upon a time I was told that those diodes' mostly fail short, not open. I had a two different pairs fail over the years and yes..they were short circuit. The radio front ends (both Ten Tec) survived:)
I am replacing the Q90 in my V3 and diodes are going to be installed.
bark less - wag more
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On 10/27/20 11:06 AM, Evan Hand wrote:
Jerry,
Thank you again.
I have done some more research and I get mixed hits on the 1n4148 vs a Schottky like 1n5819.? More important is that I see a more complex solution like this one:
Ham radio projects - a front-end protection circuit for receivers.
?Not sure the reasons for the capacitors in the circuit other to block any DC.? It might reduce broadcast input.
In the presentation from Bill Leonard (N0CU), he also has the capacitors in the Back to Back Diodes with Loss (Light Bulb) slide.? He put the red question mark on the slide, not me.
I looked up the datasheet on the 1n3600 and they are fast switching diodes similar to the 1n4148, not Schottky.
As far as I can tell, the original Back to Back diodes should work.
Aaron,
Can you check the resistance on the diodes when you remove them?? I wonder if they opened up because of overload from the nearby transmitter.? That seems to be unlikely, though I do not know the strength of the nearby station.? If it were that strong I would imagen that you have a lot of difficulty in receiving anything on the uBITX
73
Evan
AC9TU
