Sundtek DVB-C/T/T2 USB tuner - Signal Levels

[ccs]

I have noticed two oddities looking at the signal data reported by my "Sundtek MediaTV Digital Home USB Tuner Cable/Terrestrial HD (DVB-C/T/T2) " tuner as follows:

(1) The SNR values (in dB) are too high - theory says that the lock threshold should be around 20 dB rather than 80 dB indicated by the results below.

(2) The SNR in dB, the SNR expressed as a percentage of expected maximum, and the AGC always seem to have the same value.

The results were obtained using the OpenWebIf "/web/signal?AGC=" command.

Results from an Si2169 tuner (which are believed to be correct and others have found them to agree with two other models) are included for comparison".

One (and only one) terrestrial mux deteriorates when it rains, this is one of the reasons why I'm investigating these values....

Good mux, no rain, Si2169

<?xml version="1.0" encoding="UTF-8" ?>
- <e2frontendstatus>
<e2snrdb>36.70 dB</e2snrdb>
<e2snr>73 %</e2snr>
<e2ber>0</e2ber>
<e2acg>0 %</e2acg>
</e2frontendstatus>

Same good mux, no rain, SundTek

<?xml version="1.0" encoding="UTF-8" ?>
- <e2frontendstatus>
<e2snrdb>100 dB</e2snrdb>
<e2snr>100 %</e2snr>
<e2ber>0</e2ber>
<e2acg>100 %</e2acg>
</e2frontendstatus>

Susceptible mux, levels starting to fluctuate, Si2169

<?xml version="1.0" encoding="UTF-8" ?>
- <e2frontendstatus>
<e2snrdb>30.14 dB</e2snrdb>
<e2snr>60 %</e2snr>
<e2ber>0</e2ber>
<e2acg>0 %</e2acg>
</e2frontendstatus>

Susceptible mux, levels starting to fluctuate, SundTek

<?xml version="1.0" encoding="UTF-8" ?>
- <e2frontendstatus>
<e2snrdb>88 dB</e2snrdb>
<e2snr>88 %</e2snr>
<e2ber>1</e2ber>
<e2acg>88 %</e2acg>
</e2frontendstatus>

Picture goes almost completely at 82dB, BER shows low values in OpenWebif, but oscillates between 0 and 199999 in SignalFinder.

Si2169 shows this with picture almost gone...

<?xml version="1.0" encoding="UTF-8" ?>
- <e2frontendstatus>
<e2snrdb>20.97 dB</e2snrdb>
<e2snr>41 %</e2snr>
<e2ber>0</e2ber>
<e2acg>0 %</e2acg>
</e2frontendstatus>

BER stays at 0 in SignalFinder.

Both tuners were LOCKing in and out every second or so.

[EMJB]

In https://www.world-of-satellite.com/showthread.php?60879-Signal-Quality-Values (e.g. post 3) abu baniaz is reporting identical AGC and SNR% values which are at least plausible for either AGC or SNR%, but the tuner name as reported to OpenVix is subtly different from that in ccs's posts (e.g. post 13) by inclusion of ":VTUNER" at the end of the name in Abu's case.


EMJB

[EMJB]

Further to the previous posts, I have been looking further into the handling by OpenVix (and perhaps others - I have not investigated) and ccs has logged the data returned by the driver. Two points have emerged:

(1) What OpenVix Frequency Finder and OpenWebIf respectively display as "AGC" & "acg" are the signal strength reported by the driver interpreted as a percentage.


(2) With a moderate signal level (SNR ~ 33dB according to other tuners, which is consistent with distance from the transmitter etc), the SundTek driver consistently returns a value of 65535 (i.e. 0xFFFF) for the following parameters:

(a) DTV_STAT_CNR - FE_SCALE_RELATIVE (new API)
(b) snrValue (old API)
(c) DTV_STAT_SIGNAL_STRENGTH (new API)

and never supplied data for DTV_STAT_CNR - FE_SCALE_DECIBEL via the new API.

Hope this helps identify what is going wrong.

EMJB

[abu baniaz]

Best to contact Sundtek directly for their driver issue.

[ccs]

Best to contact Sundtek directly for their driver issue.
I PM'd Sundtek on Monday, hoping the message would generate an email notification, but nothing so far.

I've just attempted to open a ticket on their website, whether it got thru' I don't know, as I only gave enough clues for them to take a look on this forum.:)

[sundtek]

We have another way of reading statistics (a long time before linux statistics were even available), I think we had it documented a long time ago.

We're currently busy with finalising our upcoming products, so there won't be any time for other things until that is finalised.