[linux-dvb] voltage control for DVB-T and DiSEqC switches

Johannes Stezenbach js at linuxtv.org
Mon Jul 25 00:14:50 CEST 2005


Felix Domke wrote:
> Johannes Stezenbach wrote:
> > On Fri, Jul 22, 2005 Andreas Oberritter wrote:
> >>I want to change frontend.h in a source and binary compatible way to
> >>allow setting 5V (for active DVB-T antennas) and 12V (for DiSEqC
> >>switches which don't need 13V or 18V to switch polarization).
> > How is 12V different from 13V for DiSEqC switches?
> The point was to drain as less power as possible. 13V is probably 14V
> most of the time, so it should be a small (with 100mA, it would be
> 200mW. not really much, i agree, but one could use an unregulated 12V in
> order to avoid the step-up-step-down process which is sometimes used to
> generate the LNB voltage out of 12V) save.

That sounds like theory, in practice even advanced hardware
would have to support legacy stuff, hence you always have
the voltage conversion, right?

> But you're right, it's more a mental setting with the meaning of "stop
> that legacy crap, use diseqc, only diseqc".
> 
> > I believe most frontends don't support a seperate 12V setting,
> > or am I wrong?
> Some popular satellite receiver supports every voltage from ~12V to ~20V
> (iirc) as they use a PWM. :)

In that case, I am not opposed to adding the 12V setting.

Johannes




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