[linux-dvb] nova-t 500 tuning problems

Jon Burgess jburgess at uklinux.net
Sun Oct 29 23:21:19 CET 2006


On Sun, 2006-10-29 at 20:18 +0000, Torgeir Veimo wrote:
> On 29 Oct 2006, at 16:09, Patrick Boettcher wrote:
> 
> > Hi Torgeir,
> >
> >
> > On Sat, 28 Oct 2006, Torgeir Veimo wrote:
> >
> >>
> >> On 28 Oct 2006, at 00:35, Torgeir Veimo wrote:
> >>
> >>> Am not sure where to start looking. I've included my dmesg output  
> >>> below;
> >>
> >> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> >> tuning to 529833333 Hz
> >> video pid 0x0000, audio pid 0x01b2
> >> status 01 | signal 7abf | snr 0000 | ber 001fffff | unc 00000000 |
> >> status 01 | signal 7aab | snr 0000 | ber 001fffff | unc 00000000 |
> >> status 01 | signal 7abe | snr 0000 | ber 001fffff | unc 00000000 |
> >> status 01 | signal 7ac8 | snr 0000 | ber 001fffff | unc 00000000 |
> >>
> >
> > Can you please send your channels.conf-line for this channel?
> 
> Well, there's something weird going on with the signal I'm receiving,  
> so it might be related to that. I'd expect to find a BBC transponder  
> at frequency 505833330, but it's actually at frequency 506000. I have  
> to configure VDR to not add new transponders, as when I use the  
> channel.conf file eg from the w_scan output below, it tries to retune  
> to 5058333, and I loose the picture.
> 
> I guess it might be related to that I'm living in a block where I get  
> the signal from the socket in the wall, and there might be some kind  
> of reamplification of the tv signal. I'm just not knowledgeable about  
> dvb-t standards to understand what's going on.
> 
> Before I moved into this block, I used to have (using a roof arial)  
> in my VDR channels.conf eg.
> 
> BBC ONE;BBC:505833330:C34D34M16B8T2G32Y0:T:27500:600:601=eng,602=eng: 
> 0:0:4164:9018:4100:0
> 
> Now I have to use
> 
> BBC ONE:506000:I999B8C999D999M999T999G999Y999:T: 
> 27500:600:601,602:0:0:4164:0:0:0
> 
> Maybe someone can explain the difference between the numbers 506000  
> and 505833330? The former seems to be just a rounding of the latter,  
> but there's a digit too little..

The transmitter frequency used by any given transmitter is based on a
channel number and an offset. The offset is -167kHz, zero or +167kHz.
This is the difference that you see in the numbers.


The two links below give the channel numbers and offsets of every
freeview transmitter in the UK:

http://www.ofcom.org.uk/static/reception_advice/index.asp.html 
http://www.ofcom.org.uk/static/reception_advice/dtt_pocket_guide_2-8.pdf

To convert the channel number into a frequency, first calculate 306 +
8*N MHz, where N is the channel number. Then add or subtract 167 kHz
depending on the + or - in the tables above.

e.g. Crystal palace BBC(Multiplex 1) is show as "25 -"

	306 + 8 * 25 = 506MHz = 506000kHz

Apply the "-" offset:
	506000 - 167 = 505833kHz

So the frequency line for the Crystal palace transmitter is 505833.

It would seem the transmitter that you have now moved to is on channel
25 with no offset. The re-amplification should make no difference. I
suspect that the aerial might be taking the signal from a different
transmitter to your old one.

	Jon






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