DVB-T reception issue? Or something else?

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mattyb

254 posts

Ultimate Geek

#222959 5-Sep-2017 15:49

Hi All,

Not sure if this one should go in this forum or in the HTPC one.... moderators please move if need be.

I've been struggling with a problem with a Hauppauge WinTV-dualHD DVB-T tuner in my HTPC (running Win10 64 bit)... I've been emailing back and forth with Hauppauge tech support for the last 6 weeks or so, and basically they've told me that either my DVB-T signal is a) too weak, or b) too strong (after getting a masthead amp fitted). I've been trying to get them to advise what signal strength/quality are suitable for the device, but they can't seem to give me any numbers to verify their claims.

I'm dealing with the support out of Singapore, so I'm not 100% sure they fully understand my problem, nor am I 100% sure I fully understand it in order to explain it to them either, however what I do know is that in situation a) or b) the symptoms when testing with the Hauppauge WinTV software are the same.... picture is ok for the first few seconds, then becomes glitchy stop/start and audio goes in and out of sync. Basically unwatchable.

They've advised that I use a software tool called BDAScanChannels_UK, which I have used to analyse the freeview frequencies. The results are here:

Can't seem to get any further with Hauppauge support, so thought I'd try my luck here.

Can anyone shed any light as to whether these numbers should be ok? (btw these are with the amp fitted)

Note that I've also tried it with the amp plus an attenuator fitted, but no difference.

Many thanks in advance!

GoranZ

407 posts

Ultimate Geek

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#1859108 5-Sep-2017 16:42

Are the strength numbers measured in dBμV ?

There is a lot of debate but the "safe" level but I notice when mine drops below 60 as a Minimum I get issues. So 51~53 are just under.

A terrestrial digital TV receiver will function with an input level of between 45 and 70 dBμV. At the lower level there is a risk of interference from impulse noise from, for example, a nearby fridge or central heating switch, causing the picture to block or freeze. The recommend minimum level is therefore 50 dBμV.

http://www.horizonhge.com/reception_values.html

bales

116 posts

Master Geek

Subscriber

#1859116 5-Sep-2017 16:57

what size mamp and type are you using.

mattyb

254 posts

Ultimate Geek

#1859261 5-Sep-2017 21:31

GoranZ:

Are the strength numbers measured in dBμV ?

There is a lot of debate but the "safe" level but I notice when mine drops below 60 as a Minimum I get issues. So 51~53 are just under.

A terrestrial digital TV receiver will function with an input level of between 45 and 70 dBμV. At the lower level there is a risk of interference from impulse noise from, for example, a nearby fridge or central heating switch, causing the picture to block or freeze. The recommend minimum level is therefore 50 dBμV.

http://www.horizonhge.com/reception_values.html

I believe the strength numbers are measured in dBμV, but I'm not certain. If this is the case it seems you are suggesting that my signal level is still too low even with the amp fitted? I'll see if I can confirm the units.

mattyb

254 posts

Ultimate Geek

#1859263 5-Sep-2017 21:37

Some further information, this was received in an email from Hauppauge Support:

For DVB-T the signal strength should be between

-72dBm to -65dBm

34.8dBuv to 36.8dBuv

Rgds

Techsupport

Hauppauge Singapore

fe31nz

1228 posts

Uber Geek

#1859266 5-Sep-2017 21:39

The signal strength and quality figures provided by DVB tuners are not normally very useful except when comparing things with exactly the same tuner type, as they are not calibrated. So those numbers are pretty meaningless.

Where are you recording to? Is it a local hard disk? Is it too slow or too busy? That can cause exactly the same symptoms as reception problems.

Have you tried other software to record with (eg MediaPortal, NextPVR)?

Have you tried a different USB port? I have had a damaged USB port cause all sorts of funny problems. And sometimes other devices on the same internal USB hardware on the motherboard can interfere, so trying several other USB ports is recommended to ensure you have tried one that uses a different motherboard port.

Have you tried a different USB cable? I had one of the cables that came with a USB tuner that was ill fitting in the USB socket and used to cause trouble when someone walked by.

Does a TV plugged into the same aerial work? What is your aerial cabling topology?

It looks like the Hauppauge WinTV-dualHD will probably have an internal splitter to provide the signal to its two separate tuners. So the signal at each tuner would then be a little less than half that at the aerial input.

sbiddle

30853 posts

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Biddle Corp

Lifetime subscriber

#1859271 5-Sep-2017 21:45

Sounds more like a PC issue. Have you tried it on another device?

The Hauppage software is also very basic - I'd recommend something better such as NextPVR.

mattyb

254 posts

Ultimate Geek

#1859276 5-Sep-2017 21:55

bales:
what size mamp and type are you using.

Amp is a 15db masthead with inbuilt 4G filtering

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mattyb

254 posts

Ultimate Geek

#1859380 6-Sep-2017 08:48

fe31nz:

The signal strength and quality figures provided by DVB tuners are not normally very useful except when comparing things with exactly the same tuner type, as they are not calibrated. So those numbers are pretty meaningless.

Where are you recording to? Is it a local hard disk? Is it too slow or too busy? That can cause exactly the same symptoms as reception problems.

Yes I'm recording to a local drive. I also record to the same drive with a Hauppauge Colossus 2 through HDMI without issues, so that would indicate the drive is ok I would think.

Have you tried other software to record with (eg MediaPortal, NextPVR)?

Yes and the same issues are present. I use NextPVR a lot (with the Colossus mentioned above). The reason I'm testing using the Hauppauge software is to eliminate any potential issues with NextPVR. If I can get good glitch-free viewing in WinTV, then from experience it should be no problem with NextPVR.

Have you tried a different USB port? I have had a damaged USB port cause all sorts of funny problems. And sometimes other devices on the same internal USB hardware on the motherboard can interfere, so trying several other USB ports is recommended to ensure you have tried one that uses a different motherboard port.

Have you tried a different USB cable? I had one of the cables that came with a USB tuner that was ill fitting in the USB socket and used to cause trouble when someone walked by.

I haven't tried a different USB port or cable, will try tonight.

Does a TV plugged into the same aerial work? What is your aerial cabling topology?

It looks like the Hauppauge WinTV-dualHD will probably have an internal splitter to provide the signal to its two separate tuners. So the signal at each tuner would then be a little less than half that at the aerial input.

Yes TV plugged in works fine. UHF aerial on the roof goes to a central cupboard in the house, but is direct connected to the coax run to the TV/Media PC area. There's nothing in the way.

mattyb

254 posts

Ultimate Geek

#1859382 6-Sep-2017 08:49

sbiddle:

Sounds more like a PC issue. Have you tried it on another device?

The Hauppage software is also very basic - I'd recommend something better such as NextPVR.

Good point, I can try it on a laptop tonight.

Note comment in another reply re NextPVR above. I use it extensively with a Colossus tuner.

Rickles

2933 posts

Uber Geek

Trusted

#1859444 6-Sep-2017 09:36

I've found that some DVB cards work fine in one computer, but not in another ... even after trying several drivers etc. I suspect that some cards are just not that compatible.

Your Colossus works, but this other one doesn't, therefore trying it in another box would seem a logical good test?

mattyb

254 posts

Ultimate Geek

#1860088 7-Sep-2017 08:17

GoranZ:

Are the strength numbers measured in dBμV ?

There is a lot of debate but the "safe" level but I notice when mine drops below 60 as a Minimum I get issues. So 51~53 are just under.

A terrestrial digital TV receiver will function with an input level of between 45 and 70 dBμV. At the lower level there is a risk of interference from impulse noise from, for example, a nearby fridge or central heating switch, causing the picture to block or freeze. The recommend minimum level is therefore 50 dBμV.

http://www.horizonhge.com/reception_values.html

Hauppauge have responded that the strength numbers are displayed in dB in the software not dBμV.

mattyb

254 posts

Ultimate Geek

#1862116 11-Sep-2017 09:18

Tried the WinTV-dualHD in a laptop at the weekend and watched 10-15mins of live TV without a problem!!

Then plugged it into a different USB port (a USB3.0 one, previously it was using USB2.0) in the media PC and seems to be working fine. Weird. Will continue to monitor and see if the issue returns.

Thanks for the suggestions!

fe31nz

1228 posts

Uber Geek

#1862565 11-Sep-2017 22:29

mattyb:

Tried the WinTV-dualHD in a laptop at the weekend and watched 10-15mins of live TV without a problem!!

Then plugged it into a different USB port (a USB3.0 one, previously it was using USB2.0) in the media PC and seems to be working fine. Weird. Will continue to monitor and see if the issue returns.

Thanks for the suggestions!

Yes, "wierd" seems to be a good description of the way in which USB port interference problems show up. My guess is that the driver of one of the devices on the motherboard USB port is not handling interrupts properly and is stealing interrupts from the other devices on that port. That would explain your missing bits of recording - the interrupt was never seen and the buffer overflowed as it had not been emptied in time. But that is only a guess.

tripper1000

1617 posts

Uber Geek

#1862706 12-Sep-2017 10:46

Glad you got a solution.

For the benefit of others who may come across this thread, when you see the signal levels labelled "Quality" in digital transmission, it is generally a talking about Bit Error Rate (BER), not dBv or dBm. Some devices will report Strength (dBm/dBv) and Quality (BER) as two separate measures.

BER is basically a measure of how many of the 1's and 0's get through OK and how many are corrupted and BER relates more directly to final picture quality than strength. Some TV's, such as Sony's will report BER in its native unit - as scientific notation rather than a somewhat subjective percentage.

Signal strength naturally needs to be over a certain threshold to get a picture but can be meaningless because the signal can be strong with inference, weak with interference or strong and clear or weak and clear.

If you are pointing an aerial or dish or adjusting the gain on a mast-head amp, the quality (or clarity of the signal) can be more critical than the strength.

It is like a voice - in a quiet library a weak or quiet voice can be heard with no errors, but at a rock concert even a loud voice can be unintelligible. Conversely in a quiet library someone shouting in your ear can be unintelligible.