Some issues with (my) TBS6925

[marec]

Hi, all,

I have some questions about tbs6925, I feel these are not ok (with my unit).

First, on PC boot the card powers the LNB, and keep that state till a program turns lnb power off. Is this normal to every unit, or is something wrong with my card? The problem is the risk of burning the card or devices, connecting or disconnecting them, with power on.

Second, the locking time may take up to 25 seconds with an absent signal of low SR (less than 3,000KS). Is this normal, too?

Thanks any comments.

[marec]

So, nobody here have those issues with their 6925 cards? Do I have a broken card?

[starman345]

I have some questions about tbs6925, I feel these are not ok (with my unit).
First, on PC boot the card powers the LNB, and keep that state till a program turns lnb power off. Is this normal to every unit, or is something wrong with my card? The problem is the risk of burning the card or devices, connecting or disconnecting them, with power on.

Power on during boot is normal with mine, most dvb software allows to disable lnb if needed.

Second, the locking time may take up to 25 seconds with an absent signal of low SR (less than 3,000KS). Is this normal, too?
Thanks any comments

I'm not sure what you mean? If signal is absent then card will never lock anything. Do you mean it just takes a long time to lock signal with low SR? I don't have that problem wtih mine, it might take a little longer but certainly not 25 seconds.. Can you say what software you use? You use newest 6925 drivers?

[marec]

Hi, Starman345,
1- I think thats not good. My Prof7301 keeps lnb power off till a program uses lnb.
If nothing is using lnb, why power it? Seems a bug of TBS6925.

2- The 6925 card freezes dvb aplication while trying a frequency locking.
With bad or absent signal, it may freeze dvb player for too much time. A message like this appears "Program is not responding". Again, with the Prof7301 dont have that long wait... I use latest drivers, sure.

[steven]

Hi marec

For your first question:
Later we will have a update about this.Would you mind using this test driver:
https://hotfile.com/dl/164196647/4ff8ac1/TBS_6925_driver_setup.zip.html
It should be ok now. : )

For your second question:
This is because when lock low symbol rate it will need more time.

Kind Regards

steven

[marec]

Hi, Steven,

This update seems to fix the lnb-on after pc boot. During the boot phase there´s power to the lnb output, but when windows begins lnb power goes off. It works, but i guess, if possible, the best solution should be a firmware fix, not a driver fix...
Well, there are other issues with the card. One notorious is the signal meters efectiveness (L and Q).
The worst is the level meter. The readings range from 77 to 80, only. You can see how bad this is: try to locate a signal of a not aligned satellite, with a high symbol rate transponder (27500 or more for example). If the antenna is totally off a satellite, the level is 79; if i exactally point the satellite, signal goes to... 80 !!! In this situation, Prof7301 may go from 60 up to 90, much easier to know you found some satellite and know when have best aligned antenna to it...
Same happens with quality meter: reading ranges from 40 to 100. With the Prof7301 quality goes from 10 to 100, so you can know theres a bad but present locking signal in a antenna alignment.
So, we hope your team make more efficient meters.

[DVB]

If we talking about signal meters - i got small bug here: if I watch TV for longer time (few hours) - Level will jump suddenly to 99%, Quality will fall to 0%, but despite that - receiving is still ok. If I will switch to other frequency - Level & Quality will be back to normal values, but after some time they again switch to 99% & 0% (always the same values, no matter what frequency I will watch longer).

Reading OK:

signal_1.png (1.15 KiB) Viewed 10388 times

Reading after few hours of watching (despite values - channel still wotking, signal is present, but not reported anymore):

signal_2.png (1.01 KiB) Viewed 10388 times

About signal bars efectiveness: if You will use CrazyScan - You will see that TBS6925 RF Level values got small differences. At Hot Bird I got correct signal at RF Level 40,6 dB and no signal at 41,6 dB - just 1 dB difference. When You scan the same band from the same satellite at Prof7301 You will see, that RF Level defferences are bigger. As Level & Quality meters are based on RF Level and C/N - IMHO small differences on RF Level are reason for that. I don't know why, but I got some clue... STB6100 got some special register called BBGain. It can be changed in StreamReader.ini of CrazyScan. Changing this to -10 or 14 give bigger differences between highest and lowest RF Level, but I do not recommend to use this setting as I don't know are there any drawbacks of playing with BBGain. Of course also this will work just for CrazyScan.

EDIT: After some tests STB6100 default BBGain for TBS6925 is probably "8". Prof7301 does not react for BBGain changes - scan with default BBGain, BBGain -10 and BBGain +14 looks the same. For TBS6925 I can get highest possible RF Level on Hot Bird at ~38,5dB (BBGain 14, no signal got ~41 dB with this setting). At the same time Prof7301 got value ~33 dB (the same dish, pointed at the same satellite with the same LNB, no signal at ~37 dB)

Locking speed: yes, TBS6925 lock higher SR fast, lower SR - slow (slower than Prof7301). But well - TBS6925 can 16APSK/32APSK and correctly work with MIS on 8PSK, Prof7301 cannot. More possibilities = more combinations of FEC, modulation etc. It would be nice to see some improvements in here, but IMHO this is impossible (third generation of STV090x demod is known as slower, Prof7301 use older, second generation, which got MIS bug). Prof7301 is faster, but no MIS, no 16APSK/32APSK, and BSOD's can be seen from time to time - I haven't seen BSOD with TBS6925.

TBS6925 use STB6100 tuner. There was STV6110 tuner, but there are opinions on the web that it's efectiveness was not as good as STB6100. Now STMicroelectronics put on market STV6120 tuner. Maybe DVB card with STV6120 + STV0900AAC demod + NXP SAA7160 bridge like TBS6925 would bring new light on speed case... Some TBS6926 or something

[steven]

Hi DVB

Thanks very much for your reply

For the signal problem,we will take a test now,any progress we will give you a
reply as soon as possible.

Kind regards

steven

[crazycat]

in my soft/drivers i offer different Level/Quality calculation:

1. Technotrend-style: Level = SNR*5, Quality = f(BER):
if (!Locked) Quality = 0;
else if(BER < 10e-5) // <0.0001
Quality = 100; // 100%
else if(BER < 10e-4) // <0.001
Quality = 80; // 80%
else if(BER < 10e-3) // <0.01
Quality = 60; // 60%
else if(BER < 10e-2) // <0.1
Quality = 40; // 40%
else // >= 0.1
*pQuality = 20; // 0%

This good for monitoring locked signal or fine tunning dish.

2. Some STB-style: Level = 100+RFLevel(dBm), Quality = SNR*5.
This also good But need know modulation SNR requipment and tuner gain capabilities.

So for maximal signal info need 'extended' driver call for monitoring RFLevel(dBm), SNR (dB) and BER

[marec]

@ Crazycat,
I like the Technotrend style, but it has two problems:
1- the level meter only works after locking. Cant you allow it to work even before locking?

2 - the quality meter is stepped. Looking at it, I see it has a general "linear" formula like this Q= -20 log (BER).
As it is sems very generous, most of the time is at 100%, I would sugest a 10e-7 BER for 100% quality base formula:
Q= -14 log (BER).
I guess doing a floating point calc can be a little time consuming, but gives much precise results...