Jump to content
vramor

Input Signal Measurement

Recommended Posts

vramor

Is there any possibility to know the real Signal-to-Noise ratio in dB in company with Signal Quality in percent?

It would be very useful for optimal DVB-T aerial antenna placement and other.

Of course, for the professionals it would be very desirable to know the quantity of BER as well.

What do you mean about it?

Thanks in advance.

Share this post


Link to post
CiNcH
Is there any possibility to know the real Signal-to-Noise ratio in dB in company with Signal Quality in percent?

No way.

 

First off, manufacturers mostly won't tell you, which parameter they use to calculate the signal quality percent indicator, maybe BER (like TechnoTrend), maybe SNR (like Digital Devices), maybe Eb/No (like TeVii), or maybe something completely different. TechnoTrend for example uses SNR for the signal strength percent indicator. See how weird this is?

 

So if you knew which parameter is used to calculate which indicator, you would also have to know the formula that the manufacturer uses to calculate this specific indicator (like the signal quality percent indicator) so that you can revert it.

 

As I said, TechnoTrend uses the SNR for the signal strength percent indicator. And I even know the formula that they use:

 

% indicator = SNR in dB * 100 / 20

 

In words this means that the 100% are mapped to a 20 dB scale. So 10 dB translates to 50% for example.

So if you want to back calculate the SNR from the percent indicator in the TechnoTrend case:

 

SNR in dB = % indicator * 20 / 100

 

If you know all that for your manufacturer, you can back calculate whatever parameter they use. But it is nothing that can be guessed. You have to ask the manufacturer and if they tell you, you have to apply the rules.

 

 

Some manufacturers like Digital Devices are nice enough to log the signal parameters, like SNR in dB and signal power in dBuV.

Share this post


Link to post
QBox User

The member who was directed here from this thread

Signal Quality in DVBViewer

may have been noting the absence of ANY Signal Quality indicator in DVBViewer Pro, at least when using certain hardware. To find SQ, it's necessary to switch to TransEdit's analyzer, or use another application that can read the value from the driver.

 

Reading some of the many other posts on this topic, it seems that some users only get Quality and not Level. Perhaps there is much confusion among developers (of drivers and applications) between these two parameters.

Share this post


Link to post
CiNcH
To find SQ, it's necessary to switch to TransEdit's analyzer

And even TransEdit sometimes displays the signal strength indicator, depending on the DVB hardware (I actually don't like that because it makes the confusion even worse). Just forget about those indicators. They won't tell you anything most of the time.

 

Reading some of the many other posts on this topic, it seems that some users only get Quality and not Level. Perhaps there is much confusion among developers (of drivers and applications) between these two parameters.

Problem is the BDA specification which leaves quite some room for interpretation. What does a percent value actually tell you? Which measurement value is the percent indicator based on? Some use SNR for signal strength which is weird. So what is the benefit of those percent bars?

Share this post


Link to post
QBox User

Perhaps TransEdit is able to calculate quality directly from the error rate, or at least the "missing packets" measurements.

 

A percent indicator is useful as a relative measure. Even without an absolute reference, users can make their own correlation to what is good, bad or marginal quality. It's vital when using a positioner to maximise signal.

 

Signal strength is fairly useless for my satellite setup as it only seems to indicate the constant power level from the LNB.

Share this post


Link to post
Derrick
Perhaps TransEdit is able to calculate quality directly from the error rate, or at least the "missing packets" measurements.

Not possible cos missing packets can have other reasons than just marginal reception.

 

Signal strength is fairly useless for my satellite setup as it only seems to indicate the constant power level from the LNB.

There are other and better means for setting up a dish.

Share this post


Link to post
vramor

All the posts in this thread are very useful and friendly, but there is one question without answer.

If TransEdit can calculate and show the signal quality with a proper BDA driver of course, what does prevent from getting the same in DVBViewer?

Edited by vramor

Share this post


Link to post
Derrick
If TransEdit can calculate and show the signal quality with a proper BDA driver of course, what does prevent from getting the same in DVBViewer?

There is no technical reason. If you want both, take transedit :)

Share this post


Link to post
vramor

There is no technical reason. If you want both, take transedit :)

But I cannot see the both simultaneously, because TransEdit doesn't show the Signal Level, only the percent of Signal Quality! Maybe I'm looking at the wrong place?

Share this post


Link to post
CiNcH

I am really tired of this discussion. Maybe we should just add both bars and display whatever the driver wants us to make believe. And maybe add a warning that those numbers are useless anyway. We could just as well display some random percentage. It would be just as useful.

Share this post


Link to post
Griga
We could just as well display some random percentage

The signal strength output of my TerraTec T2 (completely meaningless values rapidly changing over a wide range) would be an excellent random number generator :) in contrast to my Hauppauge Nova S2, that outputs no signal strength at all, and the signal quality is 94% throughout, except if I disconnect the antenna cable...

 

We should implement a good signal strength placebo just to give the users something to watch. I'd say, let's start with fairly low values, and then increase them in a new DVBViewer version promising 50% more signal strength for 10 € extra.

Share this post


Link to post
vramor

Maybe we should just add both bars and display whatever the driver wants us to make believe. And maybe add a warning that those numbers are useless anyway. We could just as well display some random percentage. It would be just as useful.

It all depends on you! At any rate thanks a lot!

Share this post


Link to post
Derrick
We could just as well display some random percentage. It would be just as useful.

..not quite true :rolleyes:

 

here some shots from dvbv-pro, transedit and altdvb for the same transponder and same device/driver (TBS5925). In addition a real and meaningful reading :D

Share this post


Link to post
QBox User

My own results are consistent with Derrick's (and possibly Griga's), over every other application I try. For 28.2E, 10802H, the Signal Quality is reported as 88% in AltDVB, DVBViewer GE, Sichbo, SmartDVB and TransEdit Analyzer.

 

DVBViewer Pro is the only app I have that fails to show this, reporting instead the constant 98% that other apps report for Signal Strength. DVBSpy on 10802H shows variables #Miniepgvars.SignalStrength=0, #Miniepgvars.SignalQuality=98, so this may give a clue where things are going wrong. I'm assuming the DVB Pro main window status bar is meant to show Quality (Wiki doesn't say and there's no tool-tip as in GE).

 

My DVB-T tuner shows a similar pattern. Signal Quality is reported (probably correctly) in TransEdit and GE as 100% but in DVBPro as a more variable figure (e.g. 63 or 80) which I presume to be (once again) representative of SIgnal Strength.

DVBSpy BBC1 674000 #Miniepgvars.SignalStrength=0, #Miniepgvars.SignalQuality=63

 

So it seems, for at least three or four different tuners, DVB Pro is using the wrong parameter. Judging by the number of posts on the subject (over 300 for "signal quality"), this is confusing for many users,

 

To those who deny Signal Quality is an issue at all, I would ask: why does every receiver developer (even DVB Pro's) go to the trouble of including it? It's a very simple way to tell if you have a signal problem - without opening another window or app. It saves the user from wasting time and effort looking elsewhere for the cause. It's probably not as useful for terrestrial signals which are less prone to fading than satellite.

 

 

@Griga - are the figures for your tuners as shown in DVB Pro? If so, then they're comparable to my own. What results do you get in TransEdit or GE?

Share this post


Link to post
CiNcH

Receiver developers have to support ONE hardware, their own! DVBViewer supports some hands full of DVB hardware manufacturers with hundreds of different products. Some manufacturers just propagate 100% or some constant value for the signal indicators, some use SNR for signal strength(!), some translate 15 dB SNR to 100% quality while some would at 20 dB, some use BER for signal quality where a BER that can repaired by FEC always translates to 100%... You still can't see how meaningless this is, right?

Share this post


Link to post
vramor

Receiver developers have to support ONE hardware, their own! DVBViewer supports some hands full of DVB hardware manufacturers with hundreds of different products. Some manufacturers just propagate 100% or some constant value for the signal indicators, some use SNR for signal strength(!), some translate 15 dB SNR to 100% quality while some would at 20 dB, some use BER for signal quality where a BER that can repaired by FEC always translates to 100%... You still can't see how meaningless this is, right?

You are absolutely right, Mr.CiNcH! But if it is not too difficult for the creators of DVBViewer, maybe they could add an option of their really remarkable product with indicators similiar AltDVB. Although I will always use DVBViewer even without this option ;-)

Edited by vramor

Share this post


Link to post
CiNcH

I think we should just give the people what they want. It seems we can't teach them right... ;)

Share this post


Link to post
QBox User

Receiver developers have to support ONE hardware, their own! DVBViewer supports some hands full of DVB hardware manufacturers with hundreds of different products. Some manufacturers just propagate 100% or some constant value for the signal indicators, some use SNR for signal strength(!), some translate 15 dB SNR to 100% quality while some would at 20 dB, some use BER for signal quality where a BER that can repaired by FEC always translates to 100%... You still can't see how meaningless this is, right?

 

I see your point of view. I think we are arguing over separate issues. This thread started with a request for a SNR and I apologise for steering it away from that. I was trying to answer the new member whose own thread was closed after being directed here. I believed he was asking for something simpler - in fact, for a feature that should already exist, but may be broken.

 

Let me be clear. The OP asked for SNR but I have no interest in that and understand why it's not possible to provide it. Most users are not broadcast engineers. They wouldn't know if 15dB was better or worse than 20. They just need a simple indicator to tell them if the signal is poor.

 

DVBViewer Pro seems to have that facility but it doesn't work (at least not for all of us). Would it be hard to fix? There's no need for DVB Pro to have different interfaces for this - other BDA-compliant applications seem to manage OK.

 

In the meantime, the OP may want to download DVBViewer GE from the members' area. It may give a percent quality indicator with his hardware.

Share this post


Link to post
vramor

I've thought the subject over more carefully and made some experiments with TV tuners I could get using various viewer software. In the end I must say once more that CiNcH is absolutely right. My experiments persuaded me that the user can see the only thing concerning SQ and SL. This thing is what BDA driver from TV tuner developer can show independently of viewer software. So I think it will be the best thing to leave DVBViewer as is.

Share this post


Link to post
Likvid

I am really tired of this discussion. Maybe we should just add both bars and display whatever the driver wants us to make believe. And maybe add a warning that those numbers are useless anyway. We could just as well display some random percentage. It would be just as useful.

 

I don't you think you understand the technical concept of these values, they are useful for calibrating your dish locally, the values given was never reliable to be used as reference with other people that use other DVB cards.

 

If you install or tweak your dish it doesn't matter if these values are not spot on, they are good reference for "YOUR" setup.

 

It's pretty odd saying it's not usefull, then you don't get the idea behind it as it's actually usefull locally and never meant for being used as comparison with other setups of other people.

 

It's better to integrate the SNR/BER/GAIN indicators straight into DVBViewer application in statusbar, i always thought Transedit was a big mess, why even have a separate application? i don't get your understanding at all, why not integrate Transedit straight into DVBViewer and use one app for everything.

 

Also it's confusing for newvbies as the first thing the look for is where the signal metr is and where the Diseqc control of motor is hiding, it's not smart having it as a separate app.

Edited by Likvid

Share this post


Link to post
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...