Paul and group¡
I have said it in the past that I¡¯m no RF engineer. However I am persistent.
It made no sense to me why the receiver should be so deaf when nothing was staring me in the face. All of the transistor voltages were just about spot on.
As Paul suggested, I too thought maybe the pin diode CR301 might be shorted or very leaky. Turns out it was fine.
What else could it be?
To paraphrase an old sleuth, Mister Sherlock Ohms;
¡°After you eliminate the impossible, whatever is left, however improbable, must be the truth.¡±
So went back to the beginning and in this case that was the input to the receiver. The input does show continuity to ground, because there is a inductor ?(L1504) connected directly to the antenna connector. I checked this before, and decided it was normal.
However when I re-visited this, I removed the inductor, easy to do by taking out a nut and screw.?
And the ground remained! The bloody input was shorted to ground. No wonder the receiver couldn¡¯t hear a thing.
To condense this rather long story down, the problem with the deaf receiver was traced down to a 2¡± piece of miniature coax that connects the T/R relay to the 140 board front end. Apparently, over time, a couple of sharp braid wires managed to punch through the teflon insulator and short out the coax, and with the antenna at DC ground, it was simply overlooked.?
The UV3 can now hear a .06 uV signal and .14 uV opens the squelch.? With .3 uV, the meter deflects a bit.
Sometimes the birds do sing.
A special call out and thanks to Paul, W2NMI, for all his help in describing how this beastie works. Paul, I owe you a beer!
Mike, WB8VGE
A man with one clock knows what time it?is. A man with two clocks is never sure.
David