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pendragon

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Reply with quote  #1 
It seems there may be a fair amount of DVB-S2 16APSK and 32APSK signals already in the wild over North America. I know I don't have enough time to maintain a well-organized, compendium thread, but I thought it might be worthwhile to post some finds I've had recently. This way those of us with an interest can start the process of corralling signal types that are bound to be more common in the future. Hopefully many of these signals are up a fair amount of the time, making this process a bit easier. 

Demodulating higher-order modulations not only requires a receiving system capable of this feat, but more attention to detail in the reception path. Some will find LNBs that worked fine with 8PSK and QPSK signals, will not past muster for these. You need LNBs specified with low phase noise. Some switches will also cause problems, and proper levels and equalization of the cables may be helpful to maximizing CNR. Of course, alignment will be at a premium.

As explained in a previous thread


I cannot vouch for the reliability of these measurements, but they are repeatable. For a number of the signals I can get partial lock, others not.

These are signals that have a better chance of being fixed as I have seen each more than once, separated by hours:

72W

12076 V 1459 32APSK 3/4 Pilot On


74W

11710 H 1480 32APSK 3/4 Pilot On


79W

11936 V 1000 32APSK 3/4 Pilot On


83W

11922 H 30000 32APSK 3/4 Pilot On


87W

11918 H 2400 32APSK 3/4 Pilot On
11937 H 1021 32APSK 3/4 Pilot On


91W

12025 H 2500 32APSK 3/4 Pilot On


93W

11935 H 22500 32APSK 3/4 Pilot On


123W

11868 H 13846 16APSK 4/5 Pilot On
11968 V 1014 32APSK 3/4 Pilot On
12068 H 13846 16APSK 4/5 Pilot On


125W

11877 H 5690 32APSK 3/4 Pilot On
12012 H 2500 16APSK 4/5 Pilot On


127W

11718 H 20330 16APSK 2/3 Pilot On
11813 H 1024 32APSK 3/4 Pilot On
11847 H 4530 32APSK 3/4 Pilot On
11862 H 2500 16APSK 4/5 Pilot On


These are single sightings only:

99W

11945 V 2054 32APSK 3/4 Pilot On
11998 H 33000 16APSK 4/5 Pilot Off


101W

12159 H 1004 32APSK 3/4 Pilot On


127W

12028 H 2500 16APSK 4/5 Pilot On
mips

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Reply with quote  #2 
Nice find pendragon. Looks like we're in for an upgrade cycle...

Quote:
Originally Posted by pendragon
You need LNBs specified with low phase noise.


Would the Invacom QPH-031 be a good candidate, or is something better needed?

I noticed all signals you posted were Ku. Would a 36" inch dish be sufficient, or is something larger required for some of these signals?

ind224

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Reply with quote  #3 
I'm hoping they are all data....13+ C/N requirements would not be making me happy.
Do you lock all of them hard or do they tend to"blink". ACM is another problem for hobbyists if they change parameters on the fly due to conditions.
johbru

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Reply with quote  #4 
This page, http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/ , shows the relatively large difference between the two methods.  With power at a premium, why is 16APSK chosen?

Update:  another link, http://www.intechopen.com/download/pdf/pdfs_id/8529 explains the 4 + 12 constellation in light of recent work.  Evidently, predistortion is used to improve throughput on a given bandwidth. 

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pendragon

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Reply with quote  #5 
mips - The Invacom is a reasonably low phase-noise LNBF. You may not have to replace what you have, but I thought it was worth a caution. I found all of these on T90 toroids, which provide approximately the sensitivity of a 90cm (36") reflector at least on center. There is a bit of a drop-off for LNBs off-axis, but I only use the center 20 degrees or so instead of the advertised 40 degrees. The caveat is I will probably need one of my larger Ku dishes to successfully lock a number of these.

ind224 - 16APSK needs CNRs between around 9-14 dB and 32APSK needs 13-17 dB, both depending on FEC, to achieve a reasonably low error rate. As both modulations are specified to a maximum FEC of 9/10, the ones I found are on the lower side of CNR requirements.

johbru - 16APSK, which is not 16PSK, has certain advantages over 16QAM when dealing with non-linearities in satellite transponders. While 16APSK requires a bit more CNR than 16QAM, it's a lot better than 16PSK.
mips

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Reply with quote  #6 
Quote:
Originally Posted by pendragon
mips - The Invacom is a reasonably low phase-noise LNBF. You may not have to replace what you have, but I thought it was worth a caution. I found all of these on T90 toroids, which provide approximately the sensitivity of a 90cm (36") reflector at least on center. There is a bit of a drop-off for LNBs off-axis, but I only use the center 20 degrees or so instead of the advertised 40 degrees. The caveat is I will probably need one of my larger Ku dishes to successfully lock a number of these.


Thanks for the info. I was mentioning what I'm considering getting rather than what I have. I'd prefer getting a dish setup that will be ready for these signals so that I don't have to upgrade soon afterwards.

How big of a Ku dish do you think you'd need to lock these?

pendragon

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Reply with quote  #7 
mips - This isn't terribly scientific because I only have realistic CNR measurements for a subset of these signals. However it appears a bit less than half of the 16APSK signals should lock on my T90s (about 90cm) and the rest on my 1.2m. I rather doubt the T90 would lock any of the 32APSKs, but the 1.2m would catch about half of those, while my 1.8m Prodelin offset should get the rest.
mips

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Reply with quote  #8 
Quote:
Originally Posted by pendragon
mips - This isn't terribly scientific because I only have realistic CNR measurements for a subset of these signals. However it appears a bit less than half of the 16APSK signals should lock on my T90s (about 90cm) and the rest on my 1.2m. I rather doubt the T90 would lock any of the 32APSKs, but the 1.2m would catch about half of those, while my 1.8m Prodelin offset should get the rest.

Thanks pendragon.
pendragon

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Reply with quote  #9 
Looking for 16/32APSK signals has been a side project of mine over the past year. As was adroitly noted above I've been concentrating on Ku, but only because my toroids blanket much of the sky. However I don't mean to neglect C-band, and I'll report what I find as targets of opportunity. Here are a few that appeared on a couple of scans today:

89W

3714 V 13885 16APSK 5/6 Pilot On
3732 V 13885 16APSK 5/6 Pilot On
3750 V 13885 16APSK 5/6 Pilot On
3768 V 13885 16APSK 5/6 Pilot On
photoman76

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Reply with quote  #10 
Could you check out these two.  They might be 16/32 APSK also.
AMC 9
3870 H 13556
3888 H 13556

pendragon

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Reply with quote  #11 
Right you are photoman:

83W

3871 H 13556 16APSK 5/6 Pilot Off
3889 H 13556 16APSK 5/6 Pilot Off

Pretty good CNRs - I get consistent carrier & FEC locks on both. I need to work more on sync. Thanks!
jowski

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Reply with quote  #12 
Are there any simple patches that can be applied to the appropriate cx88* file(s) so we can see what we can lock with a prof 7301?  I suppose that after that patching exercise there's patches needed for scan-s2 and szap-s2, correct?

Thanks,
Jim


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pendragon

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Reply with quote  #13 
The module affected is actually stv0900.ko, but there is no simple patch. The original code is decent as far as Linux DVB drivers go, but unfortunately it doesn't leverage the features of this demod and there are many bugs, some of them nasty. I'm currently caught between slogging through several more waves of changes and rewriting it from scratch. 

I may be able to release "mini-patches" in the future to improve the operation of specific features like 16/32APSK, but for the moment everything is prototype-level. Parts of my code also depend on other work I've done elsewhere in the kernel to deal with design issues and performance problems. This can make it rather difficult to decouple driver changes into simple patches. 

There's a lot to be said for open-source software, but finding the time to write it isn't always practical. Once in awhile I can work on this over a weekend, but most of the time it's a matter of barely a minute here or there. Sorry  
photoman76

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Reply with quote  #14 
SES-1
11853 V 4800

This one acts like DVB-S2, but I can't lock it.



pendragon

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Reply with quote  #15 
11852 V 4800 QPSK 2/3 Pilot On - DVB-S2

I'm locking carrier, timing and FEC, but no sync. However there's plenty of signal there. Perhaps they're not sending any TS packets.
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Fellow Members, your posts are welcome here! Do not worry about posting everything perfect. Different receivers and LNB's will give you different Frequencies and Symbol Rates. Some set top boxes, PCI cards and USB receivers, Do Not Require all of the same information that others may need. It is not Required to post everything that others may need to tune in a feed. It is just most important to share the find. We can always adjust the Frequency and Symbol Rates and try the various Modulations and FEC's on our own receivers until we get a lock and then give a polite reply with what works for your receiver, as that information might help others as well. We all appreciate the efforts and energy of the Posters!

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