32 replies to this topic

[caleula]

debruis, on Apr 5 2011, 09:05 AM, said:

I did a job in Canberra a couple of weeks ago where a customer was experiencing similar problems to what you are describing. The antenna was a Digitek. I compared the SNR with the Digitek and a MM-DG16. The Digitek results were 3-5db lower than the MM. I also lowered the antenna height which also improved SNR. Hence the problems you are now experiencing with the PC tuners. They normally require a higher quality signal. I also believe the amplifier maybe overdriving the tuners in the TVs and PC tuners as well.
The only way to check this out is by site survey and signal measurements.
I can highly recommend MTV and if he is too busy let me know and I will organize a time for a visit

Appreciate your reply.

Is the MM-DG16 a Matchmaster? My original was a MatchMaster "Digital Ready" about 7 years old [it's still in the garage], however, my antenna fellow has gone off Matchmaster in favour of Digitek [Full Digital] which is pulling in South Coast without the previous small mesh array pointing in that direction. Makes me wonder a bit if the side signals aren't being tuned out.

I used to watch them building the towers when I was a boy at Cammeray. Once Channel 9 built their new 50% higher tower and pulled down the old one, the signal went way over to the units in the Manly / Mosman / Cremorne direction and the resultant ghost was 4" removed from the main image. It was then I built my own array in the high pitched c. 1900's roof rather than strapping it to the chimney. Those terracotta tiles were probably up to 60 years old and I quickly learnt the correct way to walk on them. Never cracked one, however, have a few in the shed here for when tradesman ask if I have any spares

The Samsung HD set in question also exhibited dropouts with the Matchmaster however the picture was more pixellated than the current great big chunks [squares and rectangles] now. Sound dropouts now seem longer - subjective assessment. No fade, just off and eventually back on again, long enough to lose the plot in some dramas The computer tuners were fine with the Matchmaster though.

I appreciate your kind offer. Two problems though. Obviously I don't want to tread on my current fellows toes and also like the OP in 2009, I'm a disability pensioner so money is a problem at times. Not to say I'm not keeping MTV and yourself in mind.

[mtv]

caleula,

There's a few 'variables' there.

Samsung service are very reluctant to admit some of their tuners have reception issues, even when proven the issue is in their product.

This is not to say it is actually the Samsung tuners that are the problem in your case, as you appear to have issues with signal in general.

As mentioned, USB tuners are generally very temperemental with signal, usually requiring higher signal strength and quality than most conventional tuners.

I would be inclined to think you do not have sufficient signal quality at the antenna and/or you are losing signal quality in your amplification and distribution system.

Unfortunately, without accurate signal measurements at the antenna and at various points along the way, it's impossible to determine exactly what your signals are doing.

Antenna choice and in particular, mounting position, can be critical to ensuring there is sufficient digital channel power (DCP) and high signal quality (low Bit Error Ratio).

Even moving an antenna just a few centimetres in any direction, including up/down, can mean the difference between reliable digital reception and no reception

Digital reception display basically has three stages... perfect, breaking up/pixelation and nothing. Often there's a very fine line between all three.

You don't get gradual 'fading' like you do with analogue.... digital can be perfect one second and gone the next.

This is usually because signals drop below the minimum signal parameters (eg: over the digital cliff edge).

Amplification with digital signals is generally only used to overcome distribution losses, not to try and improve poor signals at the antenna. This is why antenna selection and mounting location is so important.

When a site survey is performed, the installer should test various antennas at different mounting locations and heights, whilst measuring all digital channels and other RF sources (eg: analogue TV, FM radio, 2-way radio, pagers, etc) to determine which combination of antenna and mounting position will provide the most-reliable result.

Other forms of potential interference, such as impulse noise from power lines must also be checked and minimised.

Only once you have sufficient signal strength and quality at the antenna and based on those measurements, can you decide which amplifier (if required) will be suitable to offset any distribution losses.

If you have insufficient signal quality at the input to an amp, you'll get a stronger signal level at the amp output, but usually no improvement in signal quality, in fact, often less signal quality, as the amp will add noise to the input signal.

I'd recommend checking with your installer that he has performed all the above.

[caleula]

mtv, on Apr 5 2011, 03:11 PM, said:

caleula,

There's a few 'variables' there.

Samsung service are very reluctant to admit some of their tuners have reception issues, even when proven the issue is in their product.

... the amp will add noise to the input signal.

I'd recommend checking with your installer that he has performed all the above.

Hi mtv. Appreciate you advising as I've heard of your reputation on the forums.

Currently awaiting a Samsung home service call since replacing the circuit board, which I have now confirmed includes the tuner, has not cured the problem but rather caused it to manifest differently for the picture break up.

I asked about the amp possibly raising the noise level.

Details of the setup / test gear below. I realise not the most expensive available but surely adequate.

Rover Instruments TDA-4A OFDM-QAM TV Antenna Analyser, 44 – 870 MHz, Terrestrial Digital Analyser.

Roversat Spectrum Analyser used to test Bit Error Ratio, Flux Capacity and Side Band Interference.

The antenna fellow has done 11,000 odd installations in the last 10 years so not a " ....... Antenna" franchise.

The Samsung is a version SS02 BTW and the computer sound is now actually stuttering rather than dropping out

[mtv]

caleula, on Apr 5 2011, 04:52 PM, said:

Hi mtv. Appreciate you advising as I've heard of your reputation on the forums.

Currently awaiting a Samsung home service call since replacing the circuit board, which I have now confirmed includes the tuner, has not cured the problem but rather caused it to manifest differently for the picture break up.

I asked about the amp possibly raising the noise level.

Details of the setup / test gear below. I realise not the most expensive available but surely adequate.

Rover Instruments TDA-4A OFDM-QAM TV Antenna Analyser, 44 – 870 MHz, Terrestrial Digital Analyser.

Roversat Spectrum Analyser used to test Bit Error Ratio, Flux Capacity and Side Band Interference.

The antenna fellow has done 11,000 odd installations in the last 10 years so not a " ....... Antenna" franchise.

The Samsung is a version SS02 BTW and the computer sound is now actually stuttering rather than dropping out

The Roversat is certainly adequate for the required measurements, but it's ultimately applying those measurements to obtain the end result.

I'm not saying your local installer isn't doing what's necessary, as I am not familiar with his work, but I know of a lot of installers who have purchased excellent signal measuring equipment, but still don't even bother to check analogue signals when performing an antenna installation.

The quantity of work performed doesn't automatically mean that work is of a high standard and producing the best-possible result.

Without actually being there and having accurate signal measurements, it's impossible to know exactly what's happening, so I was just making suggestions of what to check to ensure what needs to be done has actually been done.

I don't wish to sound derogatory to your installer, but if he's as proficient as you claim he is, then I would expect him to have sorted this out for you already.

[caleula]

mtv, on Apr 5 2011, 05:18 PM, said:

The Roversat is certainly adequate for the required measurements, but it's ultimately applying those measurements to obtain the end result.

I'm not saying your local installer isn't doing what's necessary, as I am not familiar with his work, but I know of a lot of installers who have purchased excellent signal measuring equipment, but still don't even bother to check analogue signals when performing an antenna installation.

The quantity of work performed doesn't automatically mean that work is of a high standard and producing the best-possible result.

Without actually being there and having accurate signal measurements, it's impossible to know exactly what's happening, so I was just making suggestions of what to check to ensure what needs to be done has actually been done.

I don't wish to sound derogatory to your installer, but if he's as proficient as you claim he is, then I would expect him to have sorted this out for you already.

Thanks mtv. I've printed out [edited] your comments to present to him.

[caleula]

caleula, on Apr 5 2011, 07:31 PM, said:

Thanks mtv. I've printed out [edited] your comments to present to him.

Reception at 1:45AM and 3:10AM on the computer seems to be trouble free. Atmospheric conditions?

Not sure I mentioned that a Digitec set-top box with the Samsung HDTV works fine and that an approximately 7" portable TV at the computer socket also works fine.

Edited by caleula, 06 April 2011 - 03:12 AM.

[mtv]

caleula, on Apr 6 2011, 01:46 AM, said:

Reception at 1:45AM and 3:10AM on the computer seems to be trouble free. Atmospheric conditions?

Not sure I mentioned that a Digitec set-top box with the Samsung HDTV works fine and that an approximately 7" portable TV at the computer socket also works fine.

Tuner sensitivity varies, with some tuners handling poor signals better than others and some handling overloading signals better than others.

If it's an older Digitec STB eg: 2000 they were particularly deaf and required a strong, high-quality signal to receive OK, but they worked well with overly-strong signals.

Atmospeheric conditions can have an adverse effect at times, which is why it's so important to have sufficient signal strength & quality above the threshold so that when signals vary greatly, there is still sufficient in 'reserve' to allow for those fluctuations.

The most-common variation is that signals drop below the threshold, but I have also seen them go the other way, increase, causing tuner overload. The latter is particularly likely with very strong out of band signals. eg: analogue TV, FM radio, other RF sources and electrical interference.

Strong/interfering signals often cause overload in masthead amps, degrading their performance, which won't be picked up just by measuring the output of the amp.

Nothing beats being there with accurate instrumentation.

Start with the easy things first by measuring DCP BER MER & NM-C/N at the wall outlets, then at the output of the amp, then at the input of the amp and then at the antenna. If you were doing an installation you'd reverse that order.

Until you have accurate signal measurements, it's all just (educated) guesswork.

[caleula]

[quote name='mtv' date='Apr 6 2011, 10:50 AM' post='1692122']
[Tuner sensitivity varies, with some tuners handling poor signals better than others and some handling overloading signals better than others.]

[If it's an older Digitec STB eg: 2000 they were particularly deaf and required a strong, high-quality signal to receive OK, but they worked well with overly-strong signals.]

It was a brand new Digitec STB.

Samsung arranged an in-house service call and replaced the master circuit board again. They demonstrated picture interference by flicking a light switch on and off. To me this isn't a valid test and didn't break the picture up anywhere near to what we are experiencing. Since the new antenna was put up we seem to have less picture break-up. The sound breaking up is still the same, but only on the larger set.

They suggested we buy power filters so I mentioned we had been running one for a few days but the problems persisted.

Anybody know where I can buy some 75 ohm terminator plugs, not the 'F' type - the push in type?

My comments to the service company involved:

1. Flicking a light switch on and off certainly doesn't break up the picture to the same extent as we are experiencing on the larger Samsung set and we get practically no picture break up on the smaller Samsung set. Therefore I think your techs didn't check far enough into the real problem.

2. As I mentioned before, I don't recall them emulating the sound break up at all. In fact, tonight we had both sets running the same program and channel. The sound went off on the bigger set but definitely not on the smaller set. Therefore the problem would appear to be with the big set only. Is the sound circuitry on the same board as the tuner or on the board with the speakers which they didn't replace?

3. I mentioned we borrowed a set-top box for a week and had no problems. The question is why didn't the set-top have any problems?

Edited by caleula, 15 April 2011 - 11:53 PM.