[Elecraft] K2 Frequency Counter Sensitivity

[Don Brown]

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:w3fpr at earthlink.net> 
  To: Don Ehrlich<mailto:ehrlich at olypen.com> ; elecraft at mailman.qth.net<mailto:elecraft at mailman.qth.net> 
  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