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Does anybody know how to calibrate CEC firmware ?

Adrien F4IJA
 

Hi there,

I try to figure out how to calibrate the CEC firmware in order to receive good signals.

I think I have understood how to set up the master calibration : http://www.tobeca.fr/f4ija/doku.php?id=ubitx:calibration

But now, I can receive only very few signals and I have to things I can change, that are the "Set calibration" menu and the "Set the BFO" menu.

On the internet, I didn't found anything satisfying on what are they used for, what are the values you change and the impact.

In the set calibration menu, you can go up or down with negative values, but what does this value stand for ?

Also, on the Set BFO, it seems that you can adjust around 12MHz, but what for ?

Thank you a lot if you have any informations about that :-)
--
73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

David Forrest
 

The standard sources like the Tune Up page at  http://www.hfsignals.com/index.php/ubitx-tuneup/ (for v4, v5 is a bit different with the calibration, with the uBitx transmitting what it thinks is 10MHz while you detect and read the frequency from an external device) and http://www.hamskey.com/2018/05/how-to-calibration-ubitx.html tell you the mechanics of doing the calibration, but I think they miss explaining the purpose.

“Calibration / Set to Zero Beat” attempts to adjust the Raduino clock frequency to match a standard by adjusting to a reference signal.  The factory calibration likely gets you well within 10ppm, and that is close enough to work with—the frequencies indicated will be within 300Hz of the actuals, or 6 x 50Hz steps on the uBitx frequency dial.  If you chase after 1ppm accuracy, you could end up be chasing local temperature variations or remote frequency variations that are smaller than the 50Hz/30MHz=1.6ppm step of the frequency dial.

The BFO (also called "Carrier" or “usbCarrier” in the source code) is more important because it is the final IF frequency and is what gets heterodyned into audio.  V3&V4 boards use 12MHz (or 11995000Hz) and the V5 boards use about 11MHz (or 11053000Hz). Adjusting the BFO changes the IF heterodyning and with it the sideband window that gets filtered and decoded into audio, either including the carrier, warping the audio frequencies high or low, or pushing audio out of the filter bandwidth.

So, being mis-calibrated on the master calibration essentially makes your frequency reading on the dial off by a few steps or ppm, but being mis-calibrated in “BFO" interferes with the LSB/USB signal decoding and thereby the audio quality.

Dave


On Nov 7, 2019, at 9:00 AM, Adrien F4IJA <adrien.grelet@...> wrote:

Hi there,

I try to figure out how to calibrate the CEC firmware in order to receive good signals.

I think I have understood how to set up the master calibration : http://www.tobeca.fr/f4ija/doku.php?id=ubitx:calibration

But now, I can receive only very few signals and I have to things I can change, that are the "Set calibration" menu and the "Set the BFO" menu.

On the internet, I didn't found anything satisfying on what are they used for, what are the values you change and the impact.

In the set calibration menu, you can go up or down with negative values, but what does this value stand for ?

Also, on the Set BFO, it seems that you can adjust around 12MHz, but what for ?

Thank you a lot if you have any informations about that :-)
--
73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

d.maccallum@...
 

Attached please find my final cal numbers, i used the memory manager for the master cal tweaks by entering the corrected numbers directly into the display box for the calibration after i up loaded the current values from the MBITX radio then I down loaded changes and closed comm port and disconnected the USB cable. Did this till the MBITX freq display matched and tracked the display on of my KX2 radio. The BFO numbers were generated directly by cranking the numbers for best sounding audio using V1.2 CEC firmware in the MBITX radio.

Also I edited my spreadsheet calculator to handle computing the new cal number V5 last update.

You can test it and fix it if it does not work and pass it along to the group. Have fun..............

73 CU Later on the Bands....I am moving along now to install AGC control, 700 hz filter and tuning indicator..
I installed a BCI filter that I got off Amazon from RTL-SDR.com 2.6 MHz HPF Broadcast AM reject filter. I removed the filter board from it's case and wired it to the MBITX board works great! It's wired between the antenna relay and the receive relay K2 low power RX connection gonna install my AGC control in the same line..

Dave N8KZ

Adrien F4IJA
 

OK so the Set calibration is used for the Master calibration upon frequency and BFO for the decoding of signals if I'm right? 
--
73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

Adrian Chadd
 

On Fri, 8 Nov 2019 at 09:22, Adrien F4IJA <@Adrien_Grelet> wrote:

OK so the Set calibration is used for the Master calibration upon frequency and BFO for the decoding of signals if I'm right?
The BFO needs calibrating to make sure the signals you're trying to
receive are in the passband of the IF filter.

That's why you can calibrate it quickly by looking at your audio
output and just looking for the noise passband. The filters vary board
to board, so the BFO calibration can't be to a specific frequency - it
is a frequency based on what the matched crystals in your ~12MHz
filter centre on.


-adrian
(kk6vqk)

Russ KR0EHM
 

I am still struggling with this.
I've used the master calibration worksheet and that really helped. However, this was not before getting an upconverter for my SDR so I could hear myself over a dummy load. That finally got me to where I could hear the outcome of my changes to the BFO.
I’m fairly certain I have the master calibration dialed in close enough. And FT8 is on the correct sideband now so I think I’m doing better on the BFO front as well.
WSPR beacon finally works and have been my first verified spots using the ubitx.
But receiving anything is incredibly difficult. I heard plenty of CW today because of the contest. SSB is another story. Where I know there are voices to be heard, they are very faint. The entire band is solid noise. (Granted I know there are plenty of other factors - and should I verify any of those absolutely first before assuming it’s still a ubitx/cec problem?)
Is there a certain range the BFO must fall within? (v5) and could there a radio have multiple “good/decent” settings for either the master calibration or the BFO?

Russ KR0EHM
 

I am going to reassure myself of yesterday. Today was much better, and I think exploring the bands at different times and the full range of my antenna has helped.
I had more luck with WSPR and also finally got some CW spots on the RBN.  My CW spots seem to be 200hz off of what I’d expect. Is this within what would be expected or should I be able to see spot on spots?
Thanks to everyone here who reads and replies to newbs like me!