Posted by
Don Ehrlich-2 on
Sep 29, 2004; 9:59pm
URL: http://elecraft.85.s1.nabble.com/K2-Frequency-Counter-Sensitivity-tp370633.html
I am having trouble reading out the frequency of the signal at TP3,
the first step of checkout after part 2 of wiring up the RF board.
The Frequency Counter probe is fine and all components of the
frequency counter from the input through the flip-flop Q9/Q10 check
out perfectly with capacitance and ohmmeters. Supply voltage to the
flip-flop at U6-10 is 4.75 volts.
The frequency readout from the K2 varies from nothing to almost normal
(12+ MHz) depending on whether or not I have scope or frequency
counter probes attached ( The additional capacitance from the probes
increases the signal level slightly and the counter counts, but
unsteadily.
My external frequency counter reads the signal at TP3 just fine and
frequencies are within specification.
The signal at TP3 is about 2 volts peak-to-peak. Is this a normal
value? It looks marginal to me for triggering the Q9/Q10 flip-flop.
If so then the PLL Ref Oscillator has a problem.
Don K7FJ
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