[hpsdr] Calibration using Excalibur controlled by 10Mhz GPS

[Merv Thomas]

Hi,

I have set up my Excalibur board to feed a 10Mhz GPS signal into the Atlas 
Bus.  In Power SDR(KD5TFD 6Sept2010 - derived from V1.10.4 + Base SVN2025) I 
have ticked Excalibur in the set up and it correctly greys out the Mercury 
and Penelope as options but when I transmit on CW at 14.310000 Mhz into a 
dummy load and sniff the RF and measure the transmitted frequency it is 
transmitting on 14.310600 Mhz - why is this please?

To correct it I inserted an HPSDR Frequency Correction factor of 
0.9999581000 and applied it which then moved my VFO frequency to 14.310600 
Mhz.   After re-setting the VFO to 14.310000 Mhz it now transmits on exactly 
14.310000 Mhz.

Is this required?   I would have thought that the mere act of controlling it 
with an accurate GPS 10Mhz signal would have ensured a correct transmit 
frequency? GPS is a HP Z3801A.

Will be interested to learn from the "gurus" please.

Merv  VK6BMT e-mail vk6bmt at iinet.net.au