Re: BITX40 with QRPLabs VFO
|
Hi
> On my QRP-LABS DDS VFO, my correction came out to 27.010.5. So it?> was a matter of fiddling with it, and I was able to tune it in by listening to? > a known station frequency like East Cars, and calibrating the vfo so it? > sounded natural. Finally I got an on air check with my buddy cross town.? > All good. BTW I have the new corrected software on the way.
If it all works fine and you're happy with it, that's fine. But just FYI...
The 27MHz crystal in the QRP Labs Si5351A Synth kit usually oscillates between 27.003 and 27.005. I have never heard a case of it oscillating as high as 27.0105. To be absolutely correct what you would need to do is adjust the programmed IF frequency to the actual BFO frequency of your BITX40. You probably entered "IF Offset" parameter "-012,000,000" but in reality the actual BFO frequency of your BITX40 will be a kHz or more lower than that. So what you have done by setting such a high "Ref Freq" parameter (27.0105) is cancelled out the error in the IF you entered. But the cancellation will only be perfect at one particular frequency.?
It's not important - because the BITX40 only operates over a narrow frequency range anyway. I'm just saying, to really be technically perfect one should adjust the BFO frequency as well as the 27MHz Ref Freq. But I know that is not necessarily easy if you are doing it by listening to a known station frequency.
73 Hans G0UPL
|
