Posted by
Don Brown-4 on
Sep 30, 2004; 1:39pm
URL: http://elecraft.85.s1.nabble.com/K2-Frequency-Counter-Sensitivity-tp370633p370636.html
Hi
Also check that you have not reversed the pins in the frequency counter probe connector or installed the connector on the control board backwards. There was also a post recently about low gain on some of the 5179 transistors causing low sensitivity on the frequency counter.
Don Brown
----- Original Message -----
From: W3FPR - Don Wilhelm<mailto:
[hidden email]>
To: Don Ehrlich<mailto:
[hidden email]> ;
[hidden email]<mailto:
[hidden email]>
Sent: Thursday, September 30, 2004 7:21 AM
Subject: Re: [Elecraft] K2 Frequency Counter Sensitivity
Don,
I did not see an answer to your question on the reflector, so I pulled the
left side panel from my K2 and took some readings.
The peak to peak voltage at my TP3 is about 2 1/2 volts with the probe
attached and the K2 in CAL FCTR mode, so yours is within reason. This level
signal is amplified and shaped by Control Board Q9 and Q10 to a clipped and
shaped 4 volts p-p at the collector of Q10 (you can read the voltages at RP4
pins 1 thru 4). Q9 and Q10 are amplifiers rather than flip/flops - with
this front-end amplifier on the counter, it is quite sensitive and should
read input levels as low as 0.1 volts or so.
Check out the soldering on the Q9/Q10, RP4/RP5 area and you should find th
problem.
Also, check to see that the frequency probe is connected to the Control
Board properly (the shield should be nearest the left side panel).
73,
Don W3FPR
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