Re: TDA2822 Audio problem #ubitx #tda2822


Jerry Gaffke
 

What we need is a scratch built Raduino board that takes an ATMega328P chip,
an si5351, regulators for 5.0 and 3.3 volts, and has a carefully chosen frequency
on the oscillator for the processor.   Or at least a randomly chosen frequency.
No USB interface, just some pins to hook an FTDI USB-UART cable (or similar) up to the host.

Another possibility is to hang a cap across that 16mhz resonator by the ATMega328P on your stock Nano
to bring the frequency down, hopefully by a few tens of khz.
But the resonator is ridiculously small, I can't really recommend that hack to thousands of ubitx owners
with nothing but blunt instruments for soldering with.
Also, the Nano has that USB interface with a 12mhz resonator, could also be wreaking havoc with our 12mhz BFO. 
Unfortunately that's on the backside of the Nano, no chance of putting a cap across that 12mhz resonator
unless you first clip the Nano free from your Raduino.

Once the Raduino is certified free of 12 and 16mhz, we can go back to Farhan's original plan of moving the BFO
above or below the 12mhz crystal passband to select LSB/USB.  And CLK1 can remain stuck at 45+12mhz,
which should avoid some some of the extra birdies we get when it's at 45-12mhz for LSB.

Jerry, KE7ER


On Mon, Apr 9, 2018 at 03:46 pm, John wrote:
Hello Jason,

On mine, I noticed that the tone frequency would change the most when I adjusted the BFO frequency.

If you re-calibrate the BFO to a slightly different frequency, does you tone move as well?

A more complete test would be to try Ian Lee's software version 1.61 and use the IF Shift function to see if that moves your tone.

If it does, you could try to shift the IF so that the lower frequencies are emphasised and continue in the same direction until you have reversed the sideband. If in that position, after swapping the sideband in the menu you can receive signal properly without an audible tone, then we can look at swapping them in software.

If this does not work, you could try to move the first IF instead.  You could load the test version I uploaded in the files section in the  "Software based IF attenuation" folder and through the menu change the first IF and see if your tone moves in frequency.

Then we can it from there.

Good luck. This issue drove me nuts...lol.

73, John (VK2ETA)

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