KU Band Transponder gets decent signal but 0 SNR, what can be done to fix it?

Discussion in 'Free To Air (FTA) Discussion' started by enb141, Oct 25, 2018.

  1. enb141

    enb141 Topic Starter SatelliteGuys Pro
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    Guys I was able to tune a Ku Band Transponder with my Chinese 1.2m offset dish, that transponder got pretty decent signal but SNR is 0, that means is too noisy, so I would like to know if is possible to fix?
     
  2. pacificrim

    pacificrim SatelliteGuys Pro
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    If you are seeing a signal but not quality or showing 0 SNR, you are not locked on anything. Just connecting a LNB to a receiver will show a signal level. The problem could be anything like pointing, elevation, incorrect LO, etc.
     
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  3. spongella

    spongella SatelliteGuys Pro
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    Not sure what you mean by "tune;" do you mean using a meter or set top box (receiver)? More important than the signal level is the signal quality.
     
  4. harshness

    harshness SatelliteGuys Master

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    Automatic Gain Control may be amplifying low-level noise to a relatively high signal level.
     
  5. Cham

    Cham VE4GLS
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    What satellite and transponder is your dish looking at? Are you able to get a Q reading or better SNR from other TPs? Often higher order modulations require a higher signal to noise level to lock such as 8 and 16PSK. Also Forward Error Correction such as 9/10 on some TPs require a higher signal/noise level than 1/2 or 3/4. Sometimes you can squeeze an extra dB or so by adjusting skew and focal distance (LNB position in the bracket) to bring up a particular TP), but this might degrade others... but this is taking for granted the dish is aimed properly, which would be your first step in your dish setup procedure.
     
  6. enb141

    enb141 Topic Starter SatelliteGuys Pro
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    Hi guys, I'm trying to tune 116.8W @ 11800 H

    Here is the NIT

    NIT_116.8W.jpg

    Here is the BlindScan

    blind_scan_116.8W.jpg

    As you can see from the graphic, the 11800 has a decent db (-40db) which in comparison to 11480 that has about -45db and I'm able to tune that frequency but the 11800 I can't.


    Here is what I get if I try to tune 11800H

    tunning_11800H.jpg

    Sometimes SNR appears to be 0 and level seems to get lower / disappear as well
     
  7. Brct203

    Brct203 SatelliteGuys Pro

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    Can you do a spectrum scan that is more focused on 11800, so that we see what's around it?

    When you are comparing the signal at 11800 (Eutelsat 117WA) with the signal at 11480 (i think that Eutelsat 117 West B), I don't think that the -45 and -40 dB really matter. What matters is their level compared to the noise surrounding them (SNR). 8.4 dB might be a bit tight for an 8psk with FEC 3/4... i'm not sure

    I remember seeing a table that listed the minimum SNR for each variant of modulations and FEC but now i can't find it
     
  8. enb141

    enb141 Topic Starter SatelliteGuys Pro
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    Brct203, the weird thing is that I'm able to tune the higher frequencies of that NIT,

    12040 H
    12080 H
    12100 V

    All those frequencies I'm able to tune and pretty much those ones have about the same db (~ -45db)

    Here's is the spectrum from 11790 to 11810

    10800H_blindscan.jpg
     
  9. Brct203

    Brct203 SatelliteGuys Pro

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    i can't lock on that transponder either, neither can i lock on 11840 V. My Amiko does not even detect 11800. But now i'm wondering if those are maybe using some other modulation (16apsk? Digicipher?).

    Note that those appear to be on the NAFTA beam, which covers the US, Canada and Mexico, but cuts of quite sharply around Guatemala, excluding the rest of Central America
     
  10. N5XZS

    N5XZS SatelliteGuys Pro

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    Let me DX this freq, since I am in New Mexico USA.:) And figure out what the signal's formats. I will get you the signal's formats if the signal I f still there.:)
     
  11. Cham

    Cham VE4GLS
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    You likely need 10dB+ S/N in order to lock that transponder. Like Brct203 says the total signal doesn't really matter. It is the signal to noise level that is critical. According to what I see on that last graph is 2dB which is barely above the noise, however you can likely stretch out the frequency range just a bit and find a lower noise background. I have been able to lock signals in the 2-4dB range but these are DVB-S QPSK with low FEC like 1/2. 8-PSK is a different animal.
    Try playing with your dish alignment and try to get it better. EBSPro uses a really nifty Android remote app that works super well for aligning your dish.
     
  12. Cham

    Cham VE4GLS
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    11800 H 1000 DVB-S2, but modulation keeps switching between QPSK, 8PSK and 16PSK. not sure if screen cap below is readable...

    upload_2018-11-2_16-1-32.png
     
  13. Titanium

    Titanium AI6US
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    I haven't looked at the mux, but it sounds like VCM.
     
    #13 Titanium, Nov 2, 2018
    Last edited: Nov 2, 2018
  14. Cham

    Cham VE4GLS
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    Sure is.. actually ACM. It's vertical polarity too unless there is supposed to be one on horizontal as well. I'm up in Canada so the list might look different farther south.:

    Eutelsat 117 West A 116.8W 2432 TBS 6903 DVBS/S2 Tuner 1 11802 Vertical 999.83 QPSK 3/4 DVB-S2 ON 0.20 Inverted ACM 1.487 1.199 10.9 -43 MIS: 1, BER: 0.0000000, Time to lock: 613 ms 2018-11-02 5:51:19 PM
     
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  15. Brct203

    Brct203 SatelliteGuys Pro

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    it's strange that you're getting that on vertical and so narrow... what does the spectrum look like? On satsignature it's not showing anything that narrow around 11800, and 117W and 116.8 don't seem to have any beam that would bring different content to Canada (unlike 115W)
     
  16. enb141

    enb141 Topic Starter SatelliteGuys Pro
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    Guys, This is the information taken from another transponder that belongs to the same NIT

    DVB-S Orbital Position: 116.8W
    Frequency: 11.800 GHz
    Modulation: 8PSK (DVB-DSNG/Turbo/DVB-S2)
    Polarity: Horizontal
    Symbol Rate: 32720 MSps
    FEC: 3/4

    Some of you claim (Cham) that the SR is about 1000 so maybe is that why I cannot lock that transponder.

    AFAIK that transponder is intended for south america but some of you are showing another one so maybe at the center of the continent (Guatemala in my case) those two transponders unite making it impossible to lock up.

    Can somebody from the north can really tune 11.800 (I think is SR = 1000) and tell us that it is?
     
  17. Brct203

    Brct203 SatelliteGuys Pro

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    That satellite (Eutelsat 117WA) has 3 Ku beams:
    - Hemi - covers most of the Americas
    - NAFTA - US, Mexico, Southern Canada, a bit of Guatemala
    - South America - does not include Central America (cuts off in Panama)

    (there's also Eutelsat 117WB but all of its transponders are in lower Ku band)

    According to http://frequencyplansatellites.altervista.org/SatMex/Satmex_8.pdf, the Hemi beam is only above 12020 MHz

    The NAFTA and South America beams use the same frequency plan from 11700 to 12020 but don't overlap at all in coverage

    so from Guatemala, 11800H has to be the NAFTA beam, so should be the same all across North America. So the spectrum at SatSignature should be applicable to Guatemala as well as my location, and probably Cham's location, maybe with reduced power.

    PortalEDS lists a mux at 11800H32727, but since the site is more about South America than central America, I have to guess that that mux is on the South American beam.

    I don't see any other listing that shows anything at 11800H on that satellite, so maybe it's just a data transponder
     
  18. enb141

    enb141 Topic Starter SatelliteGuys Pro
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    According to that pdf file, there's two 11800 (Horizontal) frequencies, one for NAFTA and the other one is for South America, so that means why I'm getting high power (about -40db) because I'm getting some signal from both.

    Once ago I did a blind scan and as far as I remember was able to get sr = 32727, instead of the sr = 1000 that many guys in this thread were getting, so that means I'm getting more power the South America beam (that I initially tough), but I'm also getting power from the NAFTA frequency, that's why I got lots of noise.
     
  19. Brct203

    Brct203 SatelliteGuys Pro

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    I doubt you're getting the South America beam because it's supposed to end more or less near the Panama/Colombia border according to the coverage maps
    Satbeams - World Of Satellites at your fingertips
    so quite far from your location.

    Also SatSignature.com shows a wide signal on 11800H (something that looks like it could be a SR of 30000 or more). That is from the US Southwest. So my guess is that it's using some modulation that even the TBS cards can't properly detect
     
  20. Titanium

    Titanium AI6US
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    The 6922 doesn't decode ACM or VCM. I also understand that it doesn't do 16 or 32 psk. Need a different TBS card to support these formats.
     

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