[hpsdr] Frequency offset using Excalibur

[Glenn Thomas]

FWIW, I just calibrated my Flex-3000/PSDR 2.4.4 system on 10 MHz WWV. 
The prompt display of the WWV/10MHz carrier frequency is 9.999 983 MHz - 
a 17 Hz error. I also tried the phase display. Minimum rotation occurs 
when the receiver is tuned to 10.000 002 MHz. That's in CW mode with the 
25 Hz filter. Since this system has no HPSDR components except for the 
stock version of PowerSDR, I suggest that the problem may be with PSDR 
itself and not have anything to do with HPSDR.

If I repeatedly cluck the "0 beat" button I get several different 
frequencies indicated 10.000 008, 10.000 000, 10.000 014, 10.000 006, 
9.999 997, 10.000 011, 10.000.003. Of course, even ionospheric doppler 
over 60 seconds will not change the frequency of WWV that much that 
fast. Likewise, the Flex-3000 clock is unlikely to drift that far that 
fast either. Note that the tuned frequency is steady at 10.000000 MHz - 
the measured frequency is that displayed on the lower right hand corner 
of the panafall display.

I also tried the phase display. Minimum rotation occurs when the 
receiver is tuned to 10.000 002 MHz (1 Hz is the minimum step size). 
That's in CW mode with the 25 Hz filter.

Thus, even immediantly after calibration, the frequency accuracy is no 
better than a few Hz, even if the precision is much better than this.

Perhaps someone with better knowledge of PSDR can weigh in on this?

73 de Glenn WB6W



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