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Frequency error SOLVED by FW thanks to DiSlord !

 

BINGO !

After upgrading with your DFU file, i enter 100MHz in "CW" mode and

get 100.00010 MHz at the GPS locked frequency meter.

1 ppm instead of the initial -85.5 ppm !

Fine Job DiSlord and many thanks for your help and DFU file !

Best regards,

Rudi

Le 23.05.2020 ¨¤ 17:14, DiSlord a ¨¦crit?:
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23052020038.jpg

 

Good, possibly in future i add command for allow user set this correction.
 

Why not ?

As i want to replace my oscillator in the future, a good idea

to reverse to a new value !

Thank you one more time and all the best.

Rudi

Le 23.05.2020 ¨¤ 18:38, DiSlord a ¨¦crit?:
Good, possibly in future i add command for allow user set this correction.
 

That's the method HP uses in a lot of their gear. They use a very stable TCXO and to calibrate the frequency you change the divide by ratio. On my 8920 to calibrate the frequency you input a 10MHz frequency from a standard (GPS or whatever) and it compares the 2 and then changes the divide by on the internal oscillator (which doesn't run at 10 MHz) to match the reference. Very easy this way, no tweaking.
 

I agree with you. My problem was how to modify this ratio into the NanoVNA firmware; thanks to DiSlord, who modified the code with "my" oscillator value and giving to me the modified dfu file,

i was able to upgrade my NanoVNA with this file and get a very acceptable 1 ppm error instead of the previous -85.5 ppm.

Le 23.05.2020 ¨¤ 19:20, avvidclif a ¨¦crit?:
That's the method HP uses in a lot of their gear. They use a very stable TCXO and to calibrate the frequency you change the divide by ratio. On my 8920 to calibrate the frequency you input a 10MHz frequency from a standard (GPS or whatever) and it compares the 2 and then changes the divide by on the internal oscillator (which doesn't run at 10 MHz) to match the reference. Very easy this way, no tweaking.

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