Re: #uBITX Firmware KD8CEC - IF-Shift etc. #ubitx

Mike Woods


Most commercial rigs have an IF Shift or Passband Tuning (PBT) control.  This control can help with removal of QRM on receive ( eliminating a strong carrier or another station on the edge of the passband by shifting the passband up or down by a few 100 Hz. It can also compensate for a poorly adjusted frequency response on a signal that is being received (too bassy or too trebly). 

Ian’s software implements just such a control.  It functions in a similar manner to the BFO calibration routine, in fact, but unlike the calibration function, it should only operate on RX. This was the bug - it didn’t turn off on TX.  I checked on my uBITx and found the same problem here.

If you haven’t tried the KD8CEC firmware you should.  It has a number of other worthwhile software features!

73 Mike ZL1AXG

On Sun, 11 Mar 2018 at 11:32 AM, Jerry Gaffke via Groups.Io <> wrote:
I think my first post on this thread was simply incorrect.
I don't think adjusting  SECOND_OSC_USB  would fix anything.
Unless perhaps we are somehow running up against the edges of the 45mhz filter.
But then I could be wrong, I don't really understand this one yet.

I haven't messed with your code, but do plan to.
Hope to have a full digital station going, using a RasberryPi.

And hope to take a look at your code soon and give some intelligent feedback.
For now, here's some poorly thought out unintelligent feedback:

Perhaps a temporary shift of the BFO relative to the crystal filter passband 
would be a good idea.  Allows an easy zero beat of an AM station such as WWV
when calibrating the rig, for example.  Or could be used to "clarify" the reception of some ham
with a deep voice (has mostly low audio frequencies, perhaps) who has a transmitter tuned
to match it.  Other than that, I'm not sure why any sort of temporary shift would be wanted.

How does this IF-Shift feature get used?
Exactly what does IF-Shift do?


On Sat, Mar 10, 2018 at 01:31 pm, Ian Lee wrote:
I programmed something similar to what you said. I just added another setting instead of a constant(SECOND_OSC_USB).
The code is shown below.
    if (isUSB){
      si5351bx_setfreq(2, SECOND_OSC_USB - usbCarrier + f  + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_USB);
      si5351bx_setfreq(2, SECOND_OSC_LSB + usbCarrier + f + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_LSB);
Also, I would like to ask you an opinion, but now I am using the hotspot in the place where the internet is not available, so I can not use it long. 

I temporarily shifted the usbCarrier (BFO Setting value) when IF-Shift was applied.
I thought IF-Shift was a temporary function that only used for a while, so I could not satisfy both LSB and USB.
The IF-Shift value can be set to + or -, so can set the desired value according to the using mode.

Join to automatically receive all group messages.