[linux-dvb] Re: Another issue: frontend timeout value and low symbol rates

["Robert Schlabbach" <robert_s@gmx.net>]

From: "Andrew de Quincey" <adq_dvb@lidskialf.net>
> Now, I'm able to lock on to low symbol rate signals...
> I've just managed it with a 4340000 symbol rate...
> getting a REALLY good signal from it, but it took about 10 seconds
> to tune (the current timeout is hardcoded to 2 seconds). The STV0299B
> docs say it needs a certain number of symbols before being able to
> get a lock...

That can't explain the long lock time. My card is locking to the 22000 and
27500 MBaud ASTRA transponders in less than 5ms. Since 4340 MBaud is about
1/5th to 1/6th of that, the demodulator would get the same amount of
symbols in 5-6 times that, i.e. in 25-30ms. That's nowhere near 10 seconds.

But have you checked the AFC reading after the demodulator was locked on?
Low symbol rate transponders are using a much narrower frequency band than
high symbol rate ones, and thus exact tuning may be much more important. A
1MHz offset may not be much in a 30MHz band, but it makes much more of a
difference in a 5MHz band...

If possible, try compensating the offset by adjusting the tuner PLL
frequency as much as possible and see if/how that affects the lock times...

Regards,
--
Robert Schlabbach
e-mail: robert_s@gmx.net
Berlin, Germany



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