Lof1, LofSW, Lof2 in TVServer ? (1 Viewer)

[lm]

Hey M4TH... It's not that the LNB settings are different for each sat exactly, it's that I need the switch turned off for one and on for the other, and I don't completely understand how MP tells the DVB card to do that. In Mythatre, you do that by setting SW to 12700000 for one bird and 12200000 for the other. Maybe this works for MP I don't know... I suppose I could give it a try?!?

I'll PM you & try it.

 

[M4TH]

Yes that how I did it.
My awful patch was a simple batch file that changed the settings table in Ms SQL, worked but not useful, has I needed to manualy run the batch file every time I wanted to change sat.

I've opened the source, and modified the code to check satID (hardcoded for the moments)

in twinhan.cs and TVCardDVBS.cs

  if (channel.SatelliteIndex == 114)
      {//sat 91
        LNBLOFHiLoSW = 12700;
      }
      else
      {//sat 82
        LNBLOFHiLoSW = 12200;
      }

It show ok in the log (good switch freq) but doesn't work in MP...
There must be others places that use BandTypeConverter.GetDefaultLnbSetup(...)

I'll continue my search...
Math.

 

[Rhys.Goodwin]

Hi,

Can anyone give a definitive explanation of the 3 LNB override settings?

In the New Zealand forum there is a lot of confusion around this and I'd like to clear it up once and for all. Down here we use the override setting a lot since mainly we don't seem to have universal LNBs. And it seems a bit hit and miss. like "...Oh these settings worked for me but I don't really know why...."

 

[Frodo]

I will try:
A satellite consists of 1 or more transponders
Each transponder transmits 1 or more tv-channels / radio channels
A transponder is defined by:
- frequency
- fec
- modulation
- polarisation
- (and pilot/rolloff in case of DVB-S2)


The normal frequency range for satellites is 10.7GHz - 12.75 Ghz
These SAT frequencies are much too high to transport via a normal coax cable to your sat receiver.


This is where the LNB comes in.
The LNB converts the high SAT frequency to a much lower frequency
(950-2150 MHz) which can be transported via coax to your sat receiver.
To do this conversion, the LNB uses the LOF1,LOF2 and LNBSW frequencies

I'll take as an example the Astra 19.2 satellite here.
For Astra 19.2 the values are
LOF1: 9750
LOF2: 10600
LNBSW: 11700


Now suppose you want to watch a transponder at 10.7 GHz (lowest frequency)
The LNB has to down-convert this to 950 MHz.
Todo this it uses the LOF1 frequency.
the formula for this is : 10.7Ghz - LOF1(9750) = 950 Mhz

Now lets suppose you tune to the highest sat frequency (12.75 Ghz)
The LNB has to down-convert this to 2150 MHz.
Todo this it uses the LOF2 frequency.
the formula for this is : 12.75Ghz - LOF2(10600) = 2150 Mhz

Notice that now it uses LOF2.
How does it know when to use LOF1 / LOF 2?
This is mentioned by the LNBSW
for all frequencies < LNBSW the LNB will use LOF1
for all frequencyes > LNBSW the LNB will use LOF2


Now about other countries.
Not all countries use the full range of all satellite frequencies
There are several 'band' types defined.
The universal (Ku band) is the one i just described.
But besides the Ku band, we also have
- C-Band
- Circular
- North American DishPro Band Stacked Ku Hi
- North American DishPro Band Stacked Ku Lo
- North American Band Stacked Ku Hi
- North American Band Stacked Ku Lo
- North American Legacy

All those bands are slight variations on the Ku band we've described
-Some dont use the LOF2/LNBSW since the SAT frequency used is much smaller (e.g. only from 10.7GHz - 11.7GHz)
-Others use the polarisation (horizontal/vertical) to selected a frequency range
instead of the LNBSW etc.

etc

In TV3 we have pre-defined values for LOF1/LOF2/LNBSW for all these bandtypes.
However since i can only receive Ku-band satellites here i cannot verify if all other bandtypes are implemented correctly.
So any feedback on this would be nice.

For those tweakers wanting to control everything,
we added the option to tweak the LOF1/LOF2/LNBSW values







Frodo

 

[Rhys.Goodwin]

Notice that now it uses LOF2.
How does it know when to use LOF1 / LOF 2?
This is mentioned by the LNBSW
for all frequencies < LNBSW the LNB will use LOF1
for all frequencyes > LNBSW the LNB will use LOF2

Thanks very much Frodo. I think this was the part where most of confusion was. For some reason it was being confused with 22khz switch.

Cheers,
Rhys

 

[Frodo]

The 22Khz tone is not controlled directly by the TvServer

Reason for this is that there is no interface for controlling the 22KHz tone.
I believe most DVB-S(2) drivers control the 22KHz tone internally

Frodo

 

[Rhys.Goodwin]

Ok but the 22khz tone would be used for switching between LNBs right?

 

[Frodo]

I'm not 100% sure about the 22Khz tone
but to my understanding the 22Khz was used in the past to switch between
the low/hi bands

Frodo

 

[Rhys.Goodwin]

Cool. Just 1 more question! Promise!
What then is the LNB Switch parameter in the channel config used for?

 

[Frodo]

The LNB Switch parameter tells the LNB
when LOF1 and when LOF2 should be used

Use LOF1 when frequency < LNB Switch
use LOF2 when frequency >= LNB Switch

Frodo