[linux-dvb] Re: Newstruct and DVB-C with QAM_256

[Holger Waechtler <holger@convergence.de>]

Martin Neuditschko wrote:
> On Wed, Jul 03, 2002 at 09:37:21PM +1000, Bruce Janson wrote:
> 
>>    signal: signal strength, usually evaluated by the inverse gain value
>>             of the AGC circuit. This is a 16bit unsigned integer, 0xffff
>>             means a saturated AGC circuit, if you run in troubles you might
>>             want to try to install a signal attentuator between your antenna
>>             cable and the DVB card
> 
> 
> OK, I will try this. What are good values for signal strength?

You have to measure the signal strength at some frequencies in order to 
get an idea of the noise level. Thenafter every value above the noise 
level might be an analog or digital transmission, now you have to probe 
different frontend parameter configurations at this frequency.

If you receive one valid transport stream you can parse the NIT in order 
to get transmission parameter sets for other transponders/frequencies.

When you have a list of channels you can again start a brute-force scan 
in the holes between transponders, when the frequency difference is 
larger than the bandwidth there migth be other transmissions inbetween.

Holger



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