I'm Hooked! So what do the numbers mean? (1 Viewer)

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SatboyZ

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Sep 30, 2005
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On the weekend, some fine people here helped me find and lock onto RTV.

Now the obsesive compulsive comes out and I have to know how everything works. I have googled the DVB-s standard and they mostly mention the history of the standard and not what it all means.

Specifically, I want to know about symbol rate, video/audio PID, and PCR. I can understand the main frequency and polarization. Also, what are the differences in the hi/low frequency for the lnb, along with the differences between universal and standard (I know the frequency is different- why?).

Pardon me if this has been discussed before - I looked in the sub-forums and did not find the answers.

Thanks again - I have to get another optical cable so that I can get the PBS sub-channels on 125. I think motorized is the best solution - if something else pops up, a third FTA dish and my wife will shoot me.

Take Care
Steve
 

Mr Tony

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Supporting Founder
Nov 17, 2003
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Mankato, MN
Specifically, I want to know about symbol rate, video/audio PID, and PCR.
In the old analog days there was no symbol rate. You had the whole 20Mhz transponder. Scanning was easy. Scroll through the channels and if nothing was on you were done. It was also one channel per TP so the max you could have was 24 channels on C-Band, 32 on KU
Now with most of the channels being digital the symbol rate is what distinguishes the transponders since more than one digital TP can occupy that 20Mhz spot.
The higher the symbol rate the more of the transponder they are using
symbol rate of 30000 (or close) means they have the whole 20Mhz transponder

Pids are what separates the channels in the transponder. If you have more than one channel on a mux (group of channels) how would you distinguish the different channels? Have different pids :)

I can understand the main frequency and polarization. Also, what are the differences in the hi/low frequency for the lnb, along with the differences between universal and standard (I know the frequency is different- why?).
The low band of the satellite scans from 10700-11700
The high band is 11700-12900 (technically)

Universal LNB's are a necessity in Europe as they have way more channels on a satellite than we do in the US. Also 12200-12900 is reserved for DBS satellites only so all the "main" north american satellites only see 11700-12200 and are built as such. The sats over the Atlantic (58 and east) some have the lower band as they cover both North America and Europe as their footprint
 

SatboyZ

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Sep 30, 2005
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Thanks for all of your replies guys!

This is the greatest forum.

Steve:D
 

B.J.

SatelliteGuys Pro
Oct 15, 2008
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Western Maine
In the old analog days there was no symbol rate. You had the whole 20Mhz transponder. Scanning was easy. Scroll through the channels and if nothing was on you were done. It was also one channel per TP so the max you could have was 24 channels on C-Band, 32 on KU
Now with most of the channels being digital the symbol rate is what distinguishes the transponders since more than one digital TP can occupy that 20Mhz spot.
The higher the symbol rate the more of the transponder they are using
symbol rate of 30000 (or close) means they have the whole 20Mhz transponder
I agree with the gist of what Ice is saying, except for a couple things, mainly the 20 MHz thing. Except for possibly the DBS sats (which were never analog), I don't know of any sat that had 20 MHz transponders. Most C-band, and now, most Ku sats, had/have 36 MHz wide transponders. You can't fit a 30000 SR signal onto a 20 MHz transponder, as it would be over 30 MHz wide. The SR is pretty much related to the width of the signal by dividing the SR by 1000 to get the width of the signal in MHz. The frequency defines where the signal is, the SR defines how wide it is, but more importantly, it tells the receiver the rate of the data that is coming in, and is related to the bitrate as a function of whether the signal is QPSK or 8PSK, and as a function of the FEC fraction.

Also, back in the analog days, although there was only one channel per transponder on C-band, there were often more than one channel per transponder on Ku, since some of the Ku transponders had bigger bandwidths, like 54 or 72. Also, many of the Ku video channels were narrower deviation than those found on C-band, and could have bandwidths down around the low 20s MHz range, instead of bandwidths up around 30 MHz, so you could fit 2 video channels onto some Ku transponders.
This created quite a bit of non-standard-ness on Ku channels, as each Ku sat had it's own channel plan, and changing channels using the wrong sat format would end up in you being WAY off freq, or not even being able to tune the channels. There were some Ku channels that I was unable to get to with ANY of the stock sat formats on either my Echo/HT receivers or my Drake receiver, so I sometimes had to define two different sats to get all the channels. Also, even if the layout was correct, one day you'd tune in one of those double wide transponders, and there would be one channel in the center, then next day there would be a narrow channel on the high half, and another channel on the low half.... it would be different each time you'd go to the sat.


Pids are what separates the channels in the transponder. If you have more than one channel on a mux (group of channels) how would you distinguish the different channels? Have different pids :)
This is all pretty much explained in the link that QWERT mentioned, and if you pick up a cheap PCI receiver, you can see all these PIDs for yourself running the TSREADER program available there. The PIDs are just digital streams. Usually there is a Program Association Table (PAT) on PID# 0 that tells the receiver what PID# the Program Map Table (PMT) reside on. Each PMT tells the receiver which PID will have the audio, video and PCR data. The PCR is timing info that keeps the audio and video synced. The PMT data also tells the receiver whether the video is MPEG2 or MPEG4, etc, and whether the audio is MPEG or AC3 or other formats.

The low band of the satellite scans from 10700-11700
The high band is 11700-12900 (technically)

Universal LNB's are a necessity in Europe as they have way more channels on a satellite than we do in the US. Also 12200-12900 is reserved for DBS satellites only so all the "main" north american satellites only see 11700-12200 and are built as such. The sats over the Atlantic (58 and east) some have the lower band as they cover both North America and Europe as their footprint

To add to this, if you look at Lyngsat, over North America, the satellites are pretty much designated slots separated by 2 deg. Over Europe, it seems like sats are spaced all over the place, which makes you think that you'd get a lot of bleedover from one sat to the next, but since they use both the lower band and upper band, they keep things separated by not having nearby sats having signals on the same freq, whereas over North America, it is common to have the same freq in use on adjacent sats, because they keep them separated enough to avoid interferrence, unless your dish is too small.
 
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