Ubitx V5.1 frequencies below 3MHz down to 500KHz

David Forrest

I was working through the "Tune Up" page at with a bad antenna, and may have screwed up the settings.  I know that my v5 has a BFO of 11.059MHz versus the 11.996MHz in the earlier models per ( )

My questions come from the "Tune to an AM broadcast signal with known frequency." on the tune up page and unexpected tuning behavior.

On the specs say the receiver has "Continuous coverage from 500 KHz to 30 MHz"

How do you tune and read AM stations conveniently?  On my newly received, stock "uBITX v5.1", the "Band Select" slewing doesn't seem to step below 2.9MHz.

I can do fine-tuning down below 3MHz, but the MHz, KHz separation decimal separators start looking confusing below 1MHz with readings like: "LSB A: 9.490.50 " . Would this be 949.050 KHz?  

I can also seem to fine tune to "LSB A: 5.432.50_" (where '_' is a space) and then continue below past "LSB A: 4.000.50_", "LSB A: 1.998.50_" and  "LSB A: 9.995.0__" and "LSB A: 5.850.___" and down into "LSB A: 4.50.____"  The step below "LSB A: 5.0._____" rolls through "LSB A: 0..______"  back around to "USB A:42.949.672" where "Band Select" will slew down slowly, but not back up.

What's happening in these out-of-normal-range areas?  Do the filters kill off stuff below 500kHz?  What causes the tone I hear at "LSB A: 4.50"

Can I tune to frequencies in the Region 2 530-1700 kHz AM band per the clock config as on  What should LSB decoding of AM sound like?

Is there a v5 or v5.1-specific manual somewhere? 

(I just noticed that the V5.1 firmware is on github at which is a bit ahead of the webpage at


FYI: AM broadcasts occur in the HF range as well.  try evening on 7.200 or
there about.

Try 5, 10 or 15 mhz for WWV or CHU at 7.885..h thee are many other s to pick from.
you can for SW AM broadcast look up their frequency on the the 'net.

Am using USB or LSB will sound normal without any beats when correctly tuned in.

Filter do not kill below SW frequencies, the firmware in use may not work right
depending on what version.  No I've not kept track.



Because the ubitx does not have a LPF for 160 meters, the stock firmware does not hop down there in the band menu. No worries just tune fast. There is nothing to inhibit low frequency receiving. You should hear signals on 160m, and down lower hear broadcast stations by tuning in one of their sidebands.

Make sure all is okay before adjusting frequency dial calibration.  BFO much more important, see that you can tune in ssb signals, otherwise time for BFO adjustment.

Curt wb8yyy

Martin Potter

My v5.1 with stock firmware acts the same. Tuning down through 1 MHz produces dial readings of 1.000.000 followed by 9.999.50. So the loacl radio station at 580 kHz comes in a dial reading of 5.800.00. The missing digit at the end (all digits shifted one place to the left) is the key to knowing that there is an invisible decimal point before the first digit and that the displayed decimal points should be ignored.

Maybe someone could write a little script for the firmware that would fix this apparent dislay problem.

... Martin VE3OAT

David Forrest

I learned a lot from looking at the source.  The odd decimal points are controlled by this bit of code: -- it puts out the first 1 or 2 characters of the ultoa() conversion of the frequency, then intersperses the decimal points between the remaining characters.

It looks like KD8CEC uses a more robust scheme:

The way the 45MHz IF and the 11.053MHZ IF/BFO/Carrier work with the tuning and the USB/LSB is also much clearer from reading the source code.