Re: Strange tuning issue

Jerry Gaffke


If you are using stock firmware, it should arrive calibrated.
Sounds to me like your BFO frequency is not properly aligned with the passband of the 12mhz crystal filter.
Try adjusting the BFO frequency using one of the menu entries.

Unfortunately, as you adjust the BFO in the stock firmware, the radio does not adjust the VFO to keep the station tuned in.
(I believe that is the case, it has been months since I have messed with the stock firmware.  And new units might 
have different firmware now.)
So adjust the bfo until you hear audio coming through in the voice band frequencies of roughly 300 to 2300 hz,
even though the transmission remains unintelligable.  Save that bfo setting, and try the radio.

You may find that there are two settings of the bfo with the desired 300 to 2300 hz audio content,
one for LSB and one for USB.  Only one of these will give intelligible results. 

The code I now have uses the tuning algorithm here:
This makes setting the bfo, and setting the passband centers for the
45mhz and 12mhz crystal filters fairly trivial and intuitive. 
Calibrating the 25mhz reference for the si5351 is carried out as in this post:
A description of what is going on is here:

I don't know if other firmware releases have picked up on this. 


On Thu, Jun 14, 2018 at 07:52 am, jocarl011 wrote:
Hi, I have just completed the ubitx and put it into a metal case. Everything is working fine except when I try to tune in any station! When a few khz off on ssb the signal is coming in loud and strong until i start getting closer to tuning in the station and they just seem to fade away to almost nothing! When I’ve tuned the station in they are very quiet and barely audible? 

Any idea what could be wrong? 

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