Blind Scanning Receivers Question (1 Viewer)

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madmadworld

Official TV Watcher
Pub Member / Supporter
Apr 7, 2006
14,017
3,659
up on the roof in SinCity
non tech version
hardware inbeded in the box never can change... the best we've seen.
software- added after factory can be changed/updated
there has yet to be a software as good as a hardware that i have ever heard of.
kinda like factory air lol
 
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McGuyver

SatelliteGuys Pro
Apr 4, 2007
783
0
Nuclear Testing Grounds
From what I know so far is that a receiver scans the satellite I.F. frequencies and captures the TP data within each one then scans each TP for channels. The I.F. frequencies have all the info you stated that the receiver can recognize. that's about all I know, :)
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
How does blind scanning work?

What does the receiver do to determine Freq, SR, FEC, etc...?

Hmm? Well, if I were to design a receiver to do a BLIND SCAN I would first start off with the lowest frequency possible for the band that I intend to scan and the lowest symbol rate possible and ramp them both up from there.

Search 11.700 GHz Vertical from 1000 Ks/s to 30.000 Ks/s and then search 11.705 GHz Vertical from 1000 Ks/s to 30.000 Ks/s and on and on.

I would set my tuner to seek for an incoming IF frequency of 950 MHz and use a circuit to monitor the output current from the mixer stage. If the current or power is above a certain, preset value or threshold, I would then take that to be a positive signal or an indication that something is present. Then I would run a program to diseminate the signal to evaluate whether it is a compatible signal for my infrastucture. Is it a video and audio signal or just an audio signal? Or is it purely data? If it is deemed a viable signal (for TV or RADIO) then I would have the processor proceed to scan for the available channels.

Then, I would ramp the processor up to look for the next incoming IF frequency (maybe 4 MHz above the previous one) and repeat the evaluation process.

Once I have reached the end of the search for the one polarity at 12.200 Ghz or 1.450 GHz IF, then I would turn on the opposite polarity signal and repeat the search from 950 MHz to 1.450 MHz and analyze all the signals detected.

i.e. When the mixer stage within the receiver detects a current output, that means that a signal is available, so stop scanning and analyze that paticular signal and verify whether or not it is a viable TV/RADIO sat signal. If it is viable, categorize it and log it into the mix.

The FEC and symbol rate detection would have to be a part of the analyzing process. Once you detected a signal, you would have to run a whole series of tests upon it to determnine all the parameters. If you were to scan a satellite TP manually, and you detected a positive signal, you would probably try to adjust these parameters to get the best results. So the results would have to be monitored electronically with some sort of criteria to be met for each alteration. It would have to be a well written program to look at all the combinations of the variables that would be encountered and then pick the best results from that. Of course, some of the information would be found in the data stream and you could make the program pick those items out right off the bat and speed up the entire process.

If I had the capability to engineer and program a FTA satellite IRD, this is a basic (very basic) approach that I would take to facilitate a blind scan feature.

The way that I envision it, it sounds quite simplistic, but I must be missing something as many receivers don't seem to work really well with blind scanning. Only a few do an awesome job with it.

If I or anyone here really studied this subject hard, we could come up with something amazing, I think. But, alas, I am not an engineer in this realm, I am just an end user. :(

I like to chat about it though. And if anyone has a few million dollars to grant me so that I can engineer a STB that will do everything (less cook your meals), I am game for that! LOL :D

RADAR
 
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