Re: More on the cx24123

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Yeasah Pell wrote:
I've done some more testing, and I feel much more confident about my theory on the cx24123 bands. From my testing, I believe that the tuner's VCO #8 has a center frequency around 2300MHz, and is only useful when using the /4 divider (so there are effectively only 9 band selects, not 10). I think the datasheet is essentially correct in terms of showing individual band ranges, it just mixes up the assignments.

Also, I did confirm that I can tune low symbol rate signals using the original spec'd VGA offset values from the spec if the demodulator sample gain is set correctly.

I did also do some experimentation to determine the behavior of the demodulator's frequency search capability, and it definitely does do some of that, and can be controlled with the range and initial frequency parameters, but I haven't quite nailed down the exact behavior (for one thing, it looks more like +/-4MHz instead of the advertised +/-10MHz). The final thing I want to figure out before I'm satisifed with the performance of the driver is the interaction between the demodulator's frequency search and the linux dvb software zigzag.

I haven't gotten any comments on any of this so far -- is anybody actually interested in these improvements? I have no idea if this is a common card or not.

Could you send a patch with your changes to the list, so that we could
test them? I'm particularly interested in the changes to the demodulator
sample gain. I have tried different settings of that, but without
changing the VGA offset values the card did not tune well to signals
with low symbol rates.

Thanks,
Vadim Catana

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