[Elecraft] k2, freq readout calibration

[G3VVT at aol.com]

In a message dated 14/10/06 09:01:37 GMT Daylight Time, pc5m, Carel"  
<pc5m at xs4all.nl>
writes:

Verified  setting of C22 with both
methods (parallel freq counter on TP1 and  measuring the offset of TP1 and
TP2 with a 10MHz  signal).


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Hi Carel,
 
Have a care connecting an extra frequency counter in parallel with the K2  
counter as the loading capacitance of some counters may pull the readings  off 
what they really are. The K2 frequency counter via the supplied probe gives  
relatively light loading on the circuits you are measuring. The extra frequency  
counter may not cause a problem in the case of TP1, but better  to play safe 
and isolate the parallel frequency counter with a high  impedance probe.
 
I fell into this trap when setting my K2 4MHz control board clock  oscillator 
with a Racal Dane counter. This has a ovened xtal clock, hence  retains a 
fair degree of accuracy from calibration. However the extra load  capacitance of 
the frequency counter input undid all that and gave an  erroneous reading. A 
high impedance scope probe gave enough level to operate the  frequency counter, 
yet still provided sufficient isolation not to affect the  K2.
 
May not be causing problems in your case, but something to be aware  of.
 
Regards,
Bob, G3VVT