Frequency & Symbol Rate issue

[Tac2]

Hi Everyone, I'm seeking some assistance from your vast knowledge base.
Recently, I've noticed that when searching on various satellite TPs i.e. Intelsat 19, Optus D1 & D2 etc. that the Frequency & Symbol rate is different to what's listed on Lyngsat & other locations for the respective Muxs.

An example is Intelsat 19 TV Plus Mux - 12286H @30000. My receiver is showing this as 12285H @29999. Some others can be showing as up to six numbers less for the symbol rate.

The issue comes about when trying to program the receiver to known fta broadcasts plus add in new TPs as they're found. Some of this is pot luck trying to guess the numbers that will work. Blind scans do ok but seem to miss TPs at times.

Also seem not to be able to manually scan for a TP using the DVB-S2 settings, FEC rate & Modulation settings. An example was the Wizzie Mux on Intelsat 19 recently fta yet I can get any signal or quality then or even as $ now despite trying various values for the TP. At same time other TPs ok.

I've been able to manage an overall signal level between 95-100% and quality between 65-87%, depending on the satellite and only tend to have losses during heavy storm activity, otherwise it's a good picture for fta broadcasts. Located in North QLD, using a 65cm dish with sharp dual lnb (intelsat19) and a toroidal dish for (Optus D1,D2,C1/D3) via a 4xDiSeqC switch. Receiver is an Ultraplus920Hd.

I new to posting messages but have been reading the forum pages for a couple of years to learn as much as I can. Any assistance you may be able to provide with this problem is appreciated.
Thanks
Gav

[mtv]

There's often slight variations due to LBN LO stability, but it makes no difference as long as it works.

[irritant]

There's often slight variations due to LBN LO stability, but it makes no difference as long as it works.

This affects frequency for sure, but can it affect symbol rate?

[mtv]

This affects frequency for sure, but can it affect symbol rate?

The symbol rate difference will just likely to be changes not reflected in information posted on Lyngsat.

Lyngsat quite often has incorrect information... either posted incorrectly, or hasn't been updated since transponder (and sometimes even whole satellite) changes were made.

Blind scans may miss some TP's if signals (especially signal quality) is low at the time of tuning.

[apsattv]

Im going over lyngsat with a fine tooth comb and have in the past few weeks submitted a lot of local updates
Intelsat 19 ku should all be pretty accurate

As for tuner reported difference of 1 to 3mhz can be lnbf drift etc most receiver are not that fussy and can handle capturing the signal within a few mhz. Same with the Sr its more a quirk of the receiver chipset Receiver doesnt care if its 29998 or 30000.

Variables:
Intelsat 19 166.0E 1660 TBS 6983 DVBS/S2 Tuner B 12557 Horizontal Sr 14996.711 8PSK 3/4 DVB-S2 OFF 0.25 Inverted CCM 33.426 18.745 12.5 -41 MIS: 0, BER: 0.0000000, Time to lock: 304 ms 28-Dec-16 7:56:26 AM

[irritant]

Lyngsat quite often has incorrect information... either posted incorrectly, or hasn't been updated since transponder (and sometimes even whole satellite) changes were made.

Yeah, the fact that it gets updated by observers has its pros and cons. People can of course observe directly what the real stuff is on the ground, but, someone has to manually update it if it does change.

Compare with the autoscan system like the now defunct SatcoDX, who used to scan all the time to pick up anything that may have changed. However, with them one often saw duplicates, empty channels (when there really is something), frequencies changing (LNB drift at that exact moment of scanning), etc.

So, both systems has their good points and not so good points.

I wanted to ask, what actually makes the symbol rate vary? Is it something the broadcaster plays with?

[tristen]

Reported symbol rate (and also frequency) can vary a little due to slight differences in (blind scan) receivers. The stepping rate set in receiver operating software can vary by make and model. Even identical brand and model receivers will sometimes report a slightly different symbol rate or frequency.

Frequencies varying by several MHz are generally not a problem when dealing with MCPC (multi channel per carrier) signals due to the wide bandwidth involved.

SCPC (single channel per carrier) is much fussier as the bandwidth is narrow. Thus, entering 4200 MHz instead of 4203 (for a SCPC signal) will cause a problem because the receiver cannot lock onto it, but can be of little consequence with a MCPC signal.

Variations in LNB(F) local oscillator frequencies or oscillator drift due to temperature variation can also cause reception and lock problems on SCPC signals due to the signal being out of band, i.e. the receiver is unable to initially acquire lock or will lose lock over time. Generally speaking, slight LNB(F) L.O. inaccuracy or instability is better tolerated with MCPC signals.

As a matter of interest, the SatcoDX website was originally affiliated with Tele-Satellite International Magazine and was run by Christian Lyngemark. Christian left SatcoDX and started Lyngsat when SatcoDX went through a transition stage and later became Satbeams.

Both sites have always relied on contributions from observers/contributors from various locations around the world in order to update information provided.

[irritant]

As a matter of interest, the SatcoDX website was originally affiliated with Tele-Satellite International Magazine and was run by Christian Lyngemark. Christian left SatcoDX and started Lyngsat

That's right. He ran SatcoDX between 1995 and 1999. The original SatcoDX of this period had the exact same format as the Lyngsat of today, right down to the colour scheme.

[Tac2]

Thank for your replies. From the information detailed, what I thought was an issue really isn't but more with the receiver & lnbf tolerance factors.

Of interest, I deleted all stored channels from previous blind scans last night & did an automatic (limited factory settings) and a further blind scan of each satellite. I'm still comparing against Lyngsat listings. So far most for Intelsat 19 are accurate to that shown but there are a couple of TPs my receiver has scanned with frequency off by one MHz and similar for symbol rate.

I'm still to check the Optus sats & see what their listings show. I'm figuring it will be similar result though.



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[tristen]

....So far most for Intelsat 19 are accurate to that shown but there are a couple of TPs my receiver has scanned with frequency off by one MHz and similar for symbol rate.

This is normal for the reasons outlined.

....I'm still to check the Optus sats & see what their listings show. I'm figuring it will be similar result though.

Yes. Results should be similar.

Receiver software for a blind scan feature uses fixed steps rather than a linear function for determining frequency and other parameters.
A linear function would make blind scanning a lengthy procedure and is not found to be necessary in practice.
The step size can vary from receiver to receiver.

In practice, I have had some receivers fail to find some SCPC transmissions using the receivers' blind scan feature, whereas a manual scan was successful.

LNB local oscillator frequencies can vary slightly over a given time frame due to changes in ambient temperature.

Phase-locked-loop (PLL) techniques are used to stabilise local oscillator frequencies to an high accuracy on some LNB's, but PLL circuitry is more expensive to implement and so adds to production cost.

For normal consumer applications, LNB's using more conventional (and cheaper) local oscillator circuitry work well, as demonstrated by the relatively few problems experienced in practice.

[Tac2]

Thanks Tristen, yes the Optus satellite settings were similar, as suggested in your response.

A further query ... was checking alignment and signal strength today on Intelsat 19 dish. Noticed some reasonable variation between TPs on the meter. The ones listed below are all on the same Aus/NZ beam and have noted a couple of the Signal vs Quality levels i.e.
TV Plus 12286 H @30000, Signal 88%, Quality 28%.
TV Plus 12526 H @30000, Signal 88%, Quality 68% (lock light illuminated).
Wizzie 12557 H @15000, Signal 88%, Quality 13-19%.

The receiver inside can't pickup the 12557 TP but can the other two. I've tried to fine tune the dish settings and this is the best I can get. What intrigues me is the Eirp values are the same and I'm in the footprint for the beam and believe the 65cm dish is correct.

My query is why the difference in Quality level for same beam? Do they adjust the signal strength of TPs within the beam? Am I missing something with setup to correct this anomaly to have better quality strength?


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[apsattv]

If you are going by the ultraplus quality readings, it has a few major quirks mine will read up to 32% then there is gap and it will jump to %68 Your signals are not enough. Tune it up on 12726 H as its DVB-s and pretty much the strongest.

Your signals are far too low

You need at least quality %74 or better on 12286 H and 12526 H

12526 H is not a good freq to use for tuning as there is a signal on same frequency on the opposite polarity at a similar strength so if the lnbf skew is off slightly it will get nulled out.

[Tac2]

Thanks apsattv, appreciate your reply. I'm using a Satlink meter at the dish to take signal/quality readings and you're right there is definitely a difference to the receiver inside.

I changed out the lnbf and cable to new today hoping to increase signal and with meter at the dish saw a slight increase on 12726H by around 2% only. Changing skew goes in and out of tune so have fine tuned that but otherwise, for that TP I just can't get a quality level >70% on the meter. The other TPs are still low in quality level too and didnt really change.

If I compare to some of the Optus D2 TPs, with the meter at the dish, I can fine tune to peak upwards of 80-85% so I can see there's still room to improve on Intelsat19.

I'm thinking may need to go up in dish size to around 85cm but otherwise not sure what else I can do? I'm open to thoughts and suggestions. Thanks.


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[tristen]

LNB(F) skew is very critical with DVBS2, particularly if 8PSK (modulation) is in use.

I would always recommend a 90cm (minimum) dish for Ku-band as 65cm is too small for reliable reception on many transponders, particularly in changeable weather conditions.

(As an aside, a quick check of my receiver shows that I also have less signal quality on 12557H when compared to other transponders. Best transponders are 12646H, 12686H and 12726H, with signal dropping marginally on 12286H, 12526H and 12557H).

Your post leads me to assume that you have separate dishes for Optus and Intelsat satellites. Is this correct?

There is a need to bear in mind that whereas Intelsat 19 follows convention on beam polarity, Optus does not. This results in odd LNB(F) skew values for the Optus satellites when compared to others in the region.
In practice, this is not a problem if using separate dishes for each satellite, but is extremely troublesome if using an horizon-to-horizon actuator (e.g. Moteck SG-2100 or similar) with a single Ku-band dish, and therefore requiring a compromise LNB(F) skew setting.

From memory, all transponders on Optus D2 currently utilise QPSK (modulation), while many transponders on Intelsat 19 employ 8PSK (modulation), which I believe can result in lower signal quality readings (if not compensated for by increased transponder power).

If you want to delve into the topic at a more technical level, use your favourite search engine to explore the differences between QPSK and 8PSK modulation. Start with dvb.org and ETSI - the European Telecommunications Standards Institute. There are others, the names of which escape me at the moment.

I found one to get you started.... more relevant links at the bottom of the document.

Edit:
Blast!! I have discovered that the link (above) no longer works (requires login). However, all is not lost as you can access the relevant file via and clicking on the document titled DVB-S2 - 2nd Generation Satellite Broadcasting (ninth down in the left-hand column).

[Thala Dan]

Here are some readings I took recently of a few IS19 transponders whilst discussing much the same issue with another member:

12285 H – 77dBuV
12575 H – 77
12557 H - 71
12645 H - 74

As you can see, 12557 is the runt of the litter, so not surprised you're having trouble with it on a 65cm dish..

The DVB-S2 transponders on this bird have been the subject of many problems and threads on these boards............from a personal point of view they've always been a bit of a PITA.

Tristens recommendation of a 90cm dish is spot on.....that's what I'm using in NE Vic and that's pretty much what it took to get these transponders under control.

Incidentally, the readings above were taken with a Satking SK6000 meter.

[apsattv]

Also a smaller dish is probably having trouble keeping away 164E

[Tac2]

Thanks for the replies and advice.

I had some success yesterday when trying different settings and wound the lnb right out to the negative and got 12557 H at 24% quality on meter. Receiver inside can now see this TP and providing weathers good it'll hold it ... for the moment! The other TPs have lifted in quality as well. I haven't seen skew that far out before but will see how it goes.

I'll change this dish out to a 90cm when I can and as suggested that should definitely help signal. And yes running intelsat19 on a 65cm dish only and the optus d1, d2 and c1/d3 on a toroidal dish. As mentioned I did have a motek actuator on the 65cm dish a few years ago but gave up due to limited signal because of skew and alignment, thus why I separated the 4 sats received. It just seemed a lot easier and lot less trips up on the roof.

Also, thanks I'll check out the links for differences on modulation.


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