Hi,
I have been playing with 66 and 35.
66 is easy to decode with my Mini TiounerPro V2 but impossible with the RYDE.
Are there any settings I need to change?
My TX settings are DVB-S2 8 PSK, SR66, FEC3/4
35 is decodable with my TiounerPro V2 but everything has to be just wright.
The RYDE has been working excellent as my second receiver.
73's
Martin
G8KOE
RYDE and 66 and 35
Re: RYDE and 66 and 35
Hi Martin,
I may be wrong here, I often am, but I believe the Long Mynd software used by both Ryde and Portsdown does not support SR's below 125 Ks/s.
73 Dave.
I may be wrong here, I often am, but I believe the Long Mynd software used by both Ryde and Portsdown does not support SR's below 125 Ks/s.
73 Dave.
...are you sure I can't use a pair of 813's?... 
Re: RYDE and 66 and 35
66kS is the minimum symbol rate for LongMynd and its derivatives: Portsdown, Ryde, WinterHill.
It does help to have the frequencies accurately set for low SR. WH will auto calibrate the frequency variations of the LNB and NIMs whenever the beacon is selected on RX1 or RX3. The only variation then is the detected frequency of the signal determined by QuickTune. WH sets an initial tuning lock range of +/- SR/2, so a 66kS signal should always be well within tuning lock range, after calibration.
I don't how Ryde does its calibration.
For techies:
the symbol rate register in the STV0910 demodulator chip will not accept a value below 32
the master clock is 135MHz and symbol rate is given by: REG * CLOCK / 65536
so the minimum symbol rate is 32 * 135000 / 65536 = 65.918 kS
You can change the master clock frequency to achieve lower symbol rates, but that potentially requires changing the value of lots of other registers that use the value of the master clock and the chip has over 400 registers. I expect there are lots of other tweaks required for very low symbol rates, that F6DZP has discovered.
Brian
It does help to have the frequencies accurately set for low SR. WH will auto calibrate the frequency variations of the LNB and NIMs whenever the beacon is selected on RX1 or RX3. The only variation then is the detected frequency of the signal determined by QuickTune. WH sets an initial tuning lock range of +/- SR/2, so a 66kS signal should always be well within tuning lock range, after calibration.
I don't how Ryde does its calibration.
For techies:
the symbol rate register in the STV0910 demodulator chip will not accept a value below 32
the master clock is 135MHz and symbol rate is given by: REG * CLOCK / 65536
so the minimum symbol rate is 32 * 135000 / 65536 = 65.918 kS
You can change the master clock frequency to achieve lower symbol rates, but that potentially requires changing the value of lots of other registers that use the value of the master clock and the chip has over 400 registers. I expect there are lots of other tweaks required for very low symbol rates, that F6DZP has discovered.
Brian
Re: RYDE and 66 and 35
It is frustrating when people ask again and again for things the receiver can't do. Even if it could, the performance will not be good because all the filtering etc is aimed at much higher symbol rate.
If anyone really wants to do SRs below 66k I would suggest using Gnuradio and a receiver with appropriate filtering. There is an implementation of DVB-S2 available written by Ron Economos. Be aware though that as the rate is reduced it will take longer and longer to lock up because of the LDPC frame size, 68400 bits. That's a frame per second at 35ks. There are tricks to speed up the signal acquisition but everything slows down with the symbol rate. On the plus side, a CPU will find it easier to decode because there will be more CPU cycles per bit.
This isn't esoteric as DVB-S2x standards are being used for data transmission on the deep space network, admittedly at 300ks. Perhaps something like HF digital codecs sped up a bit might be better.
There are probably more optimal ways to send and receive MEPG transport streams at these very low data rates. VC systems from the 90s managed it over ISDN lines and it is just data after all. However, even an MPEG TS is probably not the best container because the use of very low symbol rates is likely to be driven by the desire to work over marginal links and a different error correction/error tolerance is needed because of the time it takes to send a frame.
Mike
If anyone really wants to do SRs below 66k I would suggest using Gnuradio and a receiver with appropriate filtering. There is an implementation of DVB-S2 available written by Ron Economos. Be aware though that as the rate is reduced it will take longer and longer to lock up because of the LDPC frame size, 68400 bits. That's a frame per second at 35ks. There are tricks to speed up the signal acquisition but everything slows down with the symbol rate. On the plus side, a CPU will find it easier to decode because there will be more CPU cycles per bit.
This isn't esoteric as DVB-S2x standards are being used for data transmission on the deep space network, admittedly at 300ks. Perhaps something like HF digital codecs sped up a bit might be better.
There are probably more optimal ways to send and receive MEPG transport streams at these very low data rates. VC systems from the 90s managed it over ISDN lines and it is just data after all. However, even an MPEG TS is probably not the best container because the use of very low symbol rates is likely to be driven by the desire to work over marginal links and a different error correction/error tolerance is needed because of the time it takes to send a frame.
Mike
Re: RYDE and 66 and 35
Hi Mike,
I find it frustrating that when I ask for help just get putdown by you.
Not everyone can be as Knowledgeable as you!
I shan't be asking for anymore help as too ignorant!
Martin
Disappointed BATC member
I find it frustrating that when I ask for help just get putdown by you.
Not everyone can be as Knowledgeable as you!
I shan't be asking for anymore help as too ignorant!
Martin
Disappointed BATC member
Re: RYDE and 66 and 35
Martin
It's not your fault - the fact that Ryde does not work at 66kS and below appears not to be properly documented. I had thought that it was, but it appears to have been lost in subsequent revisions.
Keep asking!
Dave
It's not your fault - the fact that Ryde does not work at 66kS and below appears not to be properly documented. I had thought that it was, but it appears to have been lost in subsequent revisions.
Keep asking!
Dave
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radiogareth
- Posts: 1370
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Re: RYDE and 66 and 35
Stick with it Martin, there's a lot of info in Mikes post, pretty much all of it beyond my 'pay grade' but it helped me understand why lower SR's are not the be-all and end-all of DATV. Reducing spectrum usage whilst retaining watchable video and reasonable lock times especially for marginal paths has often left me wondering why we don't just go for 33kS. Now I know.....bit like turning the FM deviation down, yes, less bandwidth but also watery quite audio.
Hence I have left my 145MHz dev at 25kHz channel spec and use 333 or 250 for nearly all my DATV contacts as it delivers 'best fit'.
Gareth
Hence I have left my 145MHz dev at 25kHz channel spec and use 333 or 250 for nearly all my DATV contacts as it delivers 'best fit'.
Gareth