Following up on my own note - the receiver basically works, I can hear the input
signal coming through the headphones. When I turn off the input 7MHz signal,
the Q22 collector goes up a bit to 6.56V. It's not a big jump from where it
was, but it is consistent and steady.
Thanks
Brian AE7JW
----- Original Message ----
From: Brian Handy <
[hidden email]>
To:
[hidden email]
Sent: Sat, January 22, 2011 10:37:29 PM
Subject: [K2] Post-Mixer signal levels
Hi all,
[hidden email]
I'm in the middle of my K2 build and have posted here before about a separate
transmitter issue. I decided to go back and check my receiver front to back to
see if I found anything, and it seems I have something ... not sure what it is
though.
With a 0.14V signal coming in, RF gain all the way down, preamp+attenuator
turned off ... I find a few things that are a bit curious.
The signals on both sides of D6 are 0.11V (the DC levels are fine). Seems I
should see a little bit different signals on both sides of that diode, and I'm
not. Following through the circuit per the signal tracing section:~
R72 - 0.128V (should be 0.077)
R73 - 0.128 (0.077)
R80 - 0.236 (should be 0.079)
Q22 Collector - 6.43V! (Should be 2.2V).
Lacking any other information, it seems the signal coming in is just a bit hot,
and this is propagated through Q22. OR, I have something oscillating here. The
frequency counter sees about 11.9Mhz on Q22 (signal generator is 7MHz).
This section of the circuit isn't all that complicated, but I'm not seeing what
the deal is. Any advice?
Cheers
Brian AE7JW
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