V5+digiboard and first calibration // paused for 20 years

Peter, DH2FBY

Hi everyone,

after having paused my activities in hamradio for about 20 years, the ubitx (and especially this group - thank you all!) got me started again. I have now „built“ a v5, added the Digi-board from, upgraded to KD8CEC v1.2. and I ran the first couple of QSOs on FT8 with a misaligned ubitx putting out <1W to my MFJ magnetic loop. Now I think I need to adjust the BFO and perform a calibration:

(Added a screenshot of the JTDX waterfall) 

1. Looking at the audio passband in JTDX, I see it being shifted about 2,5kHz to the right.
2. To get the FT8 signals into the audio passband,  I needed to set the VFO frequency to about 21.072 MHz
3. Using the bitx manager from KD8CEC, and getting the values from my bitx I see that the I2C value of the SI5351 is set to oxff. After scanning I see it is found at 0x60. VFO B is not what my bitx display shows.

Now for my questions:

For 1&2 I will probably need to adjust the bfo frequency and then use the calibrate menu from CEC. For the BFO frequency I plan to do the first shift of the passband visually in the waterfall, shifting it tot the left untill it won’t move anymore. (I tested changing the bfo which took a LOT of dialing, but after a short while at my desired frequency, the ubitx resets.) Then after saving the bfo frequency, I would look for a signal on a know frequency and use the calibrate menu to dial in. Is this the right procedure and sequence ? Any tips for a frequency/station to use as a reference for calibrating - WWV is probably not usable in Germany, right ?

For 3: Do I just set the 0x60 value manually? Is there anything I need to set before sending the values back to the bitx ? I really want to avoid bricking it now that I got so far. I wonder why the VFOB is not read correctly: 4294967295 but it was set to 14 something. MHz.

Am I on the right track ?

TIA for any help es 73

Evan Hand

I use the v6 process to calibrate my radios:  set BFO using the Ashhar Farhan video and the BFO tuning page.

1 - Set the BFO using the bfo-tuning-aid.
2 - Calibrate the rig
3 - Reset the BFO using the aid

Note: This is only with the KD8CEC software on the v5.  The stock software of the v5 puts the rig into TX mode at 10MHz.  You are then to adjust the calibration until the signal is zero beat on another receiver set to 10 MHz.  Also, you can use any AM station that you know the frequency is correct.  You just set the dial to the correct frequency before you go into the calibrate mode.

6.07 Radio Channel 292 Germany Rohrbach Waal German, Dutch, English 05:25-19:00

Assuming the frequency is correct (6.07 MHz), and you can verify that it is the correct stations, then you set the radio for 6.070000 MHz, go into calibrate mode and adjust the calibration to zero beat the station.  Press the PTT button on the mic to save the value, and then wait 10 seconds to power down.  Go back and then readjust the BFO.

When using Memory Manager:
Always start by reading the current data from the uBiTx.  I then save to a temporary file so I can go back to the starting point.
Make the adjustments
Write the values to the uBiTx.
- Close the connection in Memory Manage. IF you do not do this the then you will need to restart  Memory Manager as the commlink gets corrupted.
- Disconnect the USB cable
- Power cycle the uBiTx.
- Test the new settings.
If all is good, reconnect Memory Manager, read the values and save the file to a known location in case you need to replace the Nano in the future. (The calibration parameters are mainboard specific and can be transferred to another Nano with the same results.

I hope this helps.

Peter, DH2FBY

Hi Evan,

and thank you very VERY much for the comprehensive answer - I was not hoping nor expecting this :)

Now I'm stuck at step one (using the tuning aid)  already: says to tune the knob until the noise graph is centered between the two red lines (which I did). But: in the video you can see Ashnar tune the passband to the left until it starts shifting right again. At least on my setup, this is not the same!

Partial success though: after tuning to the middle of the 300Hz-3kHz, the output power on 15m FT8 went up to about 4W.

What is the "right way" ? Tune COMPLETELY to the left, or center between the lines ?


Evan Hand

The answer depends on what you are optimizing. For digital modes, you want it as centered as possible. This is driven by the pass band of the SSB filter being less than 2700 Hz.  Digital modes can go from 200 to 4000+ Hz. 

For SSB, you would adjust for best sound based on your preference. 

For CW you may want to narrow the reception by optimizing for less than 1000 Hz, creating a more narrow receive range at the expense of SSB sound/signal quality.  With CW you do not need to worry about carrier suppression.

Since I do both SSB and Digital, I have centered the pass band between 300 and 3000 Hz as Ashhar Farhan has suggested. When I have my code speed up I have an audio filter to install for that mode. 

Of note, the KD8CEC Nextion software allows some of these adjustments to be done without having to go back and recalibrate. It has an IF shift function that can adjust where the signal is in relation to the SSB filter sweet spot.