Re: Digital BFO Mod: Terrible Audio! #bitx40help


Ryan Flowers
 

See, this is why I posted. I know I'm in over my head. I don't fully understand the crystal filter and where its passband is positioned. You just gave me good information though, so thank you. And Tim, the variables and equation used is

 vfoOffset + frequency)
VFO Offset of 11984800 + frequency displayed (7mhz) and oh my, I just realized I'm doing it backwards which is one reason I am having such a hard time. I do most of this late at night and it shows lol. Thanks for causing me to re-evaluate that. This would explain why I was getting FT8 only in what I thought was LSB mode. I modified the code to subtract displayed frequency from carrier, outputting 5mhz instead of 19, and adjusted the USB/LSB frequencies based on what you said Jerry, and they were dead on. 

I fired up the rig and did some basic testing and the audio was very clean. I hooked up the PC and had an FT8 QSO by answering nearly the first CQ I saw. Success! Thanks so much for the help, guys. 

I still want to understand how the 5 crystals all being on the same frequency works. I think the X5 crystal has a capacitor to pull the frequency up to adjust the passband, and the 119984800 which I mistakenly thought was my offset is not, but is rather the original LSB frequency I was *using* as the offset on my QRP Labs VFO. Because now I'm seeing that I'm a few khz low on the display, which I suppose makes sense since my offset is equally low. I have some adjusting to do.

Thanks again- you guys have saved me tons of frustration.

--
Ryan Flowers - W7RLF
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