[Skimmertalk] The importance of frequency calibration

[Pete Smith]

When using Skimmer to send spots to your contest logger, it's important to 
calibrate your SDR fairly accurately.  Otherwise you will find that when 
you jump to a Skimmer spot, it will always be a little off frequency, and 
if you're feeding Skimmer spots along with those from the cluster network, 
then you'll get duplicate spots on your bandmap.

Fortunately, the SoftRock receivers can be calibrated with sufficient 
accuracy simply by listening to signals on your regular transceiver and 
then adjusting the center frequency in Skimmer until the beat notes and 
frequency readouts agree.  In SoftRock-IF mode, you can do the same using 
the "Audio IF" frequency.  With the SDR-IQ, you can either use Skimmer's 
calibration routine or the one in Spectravue.  There is one important 
difference, though - Skimmer's correction is stored in the CW Skimmer.ini 
file, while Spectravue's correction is both stored in an .ini file and 
written to the SDR-IQ's internal EEPROM.  What can happen, as a result 
(it's happened to me) is that when using  Skimmer its calibration 
correction is applied to the corrected local oscillator frequency 
controlled by the EEPROM, resulting in an apparent double error.  I suggest 
you use Spectravue's and then delete the frequency correction from the 
CWSkimmer.ini file.

73, Pete N4ZR
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