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Sideband rejection

 

After relay change my uBitx 4.3 is now capable for legal CW QSOs. So I did the next step and changed L5,L7 and L1 to 680 / 330 nH.
The first test on SSB via dummyload and 20db extra attenuation direct in the antenna of my good old SDR-IQ shows a rather clean signal in the RF spectrum at 10kHz width - but looking like AM and not like LSB on 3.6 MHz. Test with other stations confirmed that. The carrier is still present and the USB sideband is only 6dB down compared with LSB.
Surely the BFO must be corrected. But how? I followed the instructions, got a AM station with known frequency and set BFO to zero beat. Was then happy, to have a clean reception of all SSB stations on the QRGs where they were spotted.

73 Matthias, DD7NT
 

I don't know what firmware you are using or what instructions you are following.
Tuning for zero-beat makes sense to me when calibrating the si5351 reference oscillator
so the rig is on the correct frequency.
But tuning for zero-beat does not make sense when setting the BFO offset with respect to the 12mhz filter.

I don't think many firmware releases calibrate using algorithm of post???/g/BITX20/message/54501
or tune the rig following the algorithm of post??/g/BITX20/message/44278
That being the case, there may be weird dependencies between calibrating and setting the BFO,
I suggest you set the BFO first, then calibrate the rig to be on the correct frequency.

To set the BFO, I suggest you tune in an amateur SSB station, then set the BFO for best received audio.
Ideally, find a station where the operator's voice is similar to your own (low, medium, or high pitched).
When transmitting, the filter will be doing the same thing to your voice as rig does when receiving.

Jerry?


On Mon, Oct 29, 2018 at 08:55 AM, Matthias Zwoch wrote:
Surely the BFO must be corrected. But how? I followed the instructions, got a AM station with known frequency and set BFO to zero beat.??
 

Better yet, repeatedly do both steps until no further adjustment is needed.
I have no idea how the two different adjustments might affect each other with the firmware you are using.


On Mon, Oct 29, 2018 at 09:17 AM, Jerry Gaffke wrote:
I suggest you set the BFO first, then calibrate the rig to be on the correct frequency.
 

Set the BFO to 11.9965 and see if that works.

At 29-10-18, you wrote:
After relay change my uBitx 4.3 is now capable for legal CW QSOs. So I did the next step and changed L5,L7 and L1 to 680 / 330 nH.
The first test on SSB via dummyload and 20db extra attenuation direct in the antenna of my good old SDR-IQ shows a rather clean signal in the RF spectrum at 10kHz width - but looking like AM and not like LSB on 3.6 MHz. Test with other stations confirmed that. The carrier is still present and the USB sideband is only 6dB down compared with LSB.
Surely the BFO must be corrected. But how? I followed the instructions, got a AM station with known frequency and set BFO to zero beat. Was then happy, to have a clean reception of all SSB stations on the QRGs where they were spotted.

73 Matthias, DD7NT
 

Am 30.10.2018 um 06:43 schrieb Raj vu2zap:
Set the BFO to 11.9965 and see if that works.
Thanks Raj !

Had again to correct the calibration which was exactly 1 kHz off. After playing a while with Sunils calibration method I got it calibrated on 10,000.000 and then played with the BFO. Tested all BFO values from 11.995.0 to 11.996.5
The best result I got at 11,995.3 with -28 dB sideband rejection both on USB, LSB, full carrier rejection and nearly equal and good sound qualitiy on USB and LSB. The bandwidth was about 3 kHz.

73 Matthias, DD7NT

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