[linux-dvb] Development of a mobile system for automatic positioning of a dish antenna.

Felix Domke tmbinc at elitedvb.net
Wed Aug 3 01:28:10 CEST 2005


Hi,

Johannes Stezenbach wrote:
> On Mon, Jul 25, 2005 Guy Roussin wrote:
>>For an itinerant platform we are trying to develop a simple system for 
>>automatic positioning of a satellite dish antenna equipped with motors and 
>>a linux PC with
>>dvb-s card, digital compass, inclinometer and GPS.
> This sounds like a fun project, but I think there's a problem:
> Digital demodulators will only give you useful signal status
> information when they are already locked to a signal. You can
> then optimize the dish pointing by using the signal indicators
> provided by the demodulator. But the dish angle where the signal is
> strong enough is rather narrow, which makes it difficult to use
> this for seeking the satellte. I think that using analog equipment
> is better for this job.
Hm,

you can use AGC information, they are available even without any lock.

For example, pictures like
http://developer.elitedvb.net/files/76/shot1.png were made with a normal
stv0299 based frontend, using the AGC information.

I know that AGC isn't as good as a decent SNR or something, but with a
given setup (and provided that there won't be any overamplifications),
so that the only moving part is the dish itself, it should correspond
more-or-less to the signal quality.

you can still fine-tune with the SNR/BER after you found a valid
transponder.

Felix




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