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Maximum Dcp Before Failure


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Here's the scenario

Customer has bought new Digital TV.Its not working on present antenna.(either crusty old one or they never had one ,only rabbit ears)

You put your meter on the antenna lead and confirm that the signal is no good.

You install new digital antenna ( designed for the channels only that is available from the desired transmitter)Obviously you know what you are doing and are not a cowboy.

Ch BER <2E-05 all channels

DCP 60-65 dBuV all channels

No out of band signals greater that 50dBuv

Perfect !! Text book signal . :rolleyes:

You plug it in only to find that one or more channels are braking up or "no signal " ( if it will tune at all ) :o

You re-check with your meter and yes its perfect ,it should work .You even plug in a STB and it works perfectly.

Out of desperation you attenuate signal and find if you wind it down to around 50dBuv or even lower it all starts working .

Question:

Do you tell customer that in your opinion "this TV is not up to spec (a piece of ****) and they should get it looked at under warranty ( knowing that its likely to sit at a repair shop for 6-8 weeks and likely to be bounced back "no fault found -get your antenna checked" )

OR .. Do you just fit an attenuator and say "I think this set is faulty" explain the likely scenario of trying to get it repaired and suggest they just go with the attenuator and hope it doesn't get any worse

OR ... fit the attenuator and say nothing

Occasionally I am finding this problem .

Now we all know that TOO MUCH signal is an issue ( generally above 80dBuV ) but where do you draw the line and decide that a particular device is faulty ??

50dBuv ,55 dBuv ,60dBuv ,65dBuv,70dBuV even ?

I have seen some STB's that can handle almost 100dBuV without any issues so why are some TV's sooo touchy ??.

Having also been a workshop tech I have seen the other side of things too.

Often workshops have many outlets splitter after splitter and insufficient signal levels at multiple outlets and this sort of fault would not be picked up in a typical workshop setup. SAD BUT TRUE .

(In analog days it was preferable to have a borderline snowy ( weak) signal so that issues such as broken tuner connections etc would show up where as a strong signal would mask these things)

You plug it in ( the suspect Digital TV) and all channels work OK ,you put it on test and after several hours conclude that its OK .( so its most likely a fault at the customers place).warranty claim form filled in . Next job please

How are other installers seeing this issue?

Edited by bellotv
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How are other installers seeing this issue?

I drag the explorer out from the van and show the customer I'm getting perfect pictures.

I then advise them to get a proper brand of TV, and ask them to get the retailer to refer back to me if necessary.

Link to something from the past.

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I have seen this occur where an adjacent analogue channel has caused interference to the digital channel.

The meter indicates all good measurements, like your description, but the TV tuner isn't happy.

This is where a meter with an A/V display is very useful.

I've had similar experiences where I have been able to demonstrate with the Unaohm AP-01 that signals/reception are excellent.

Testing with a STB in your case has also confirmed the issue is with the TV tuner.

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So have I, and also with adjacent digital channels, when the levels are out of whack.

Sure but when they are not and when there are no adjacent analog channels. And when the adjacent digital channnels are equal .This is my issue .

Why is this shite put on the market ?.

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I have found a similar issue with a Compro U80 USB PC receiver. At levels over about 53dbuv it is simply not capable of reliable UHF reception even where there is no adjacent analogue transmission to worry about. The device's VHF performance is totally different and will tollerate beyond 85dbuv without raising an eyebrow. Its own signal level reporting cuts off at 50dbuv.

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Out of desperation you attenuate signal and find if you wind it down to around 50dBuv or even lower it all starts working .

Is that at UHF only?

I ask because I've only seen the problem at UHF (and in the light of DrP's comment.)

(As an aside, earlier this year, I had a few sets that wouldn't work on UHF digital channels unless the the signal was >50dBµV, which required mastheads to be fitted. I put this down to perhaps the UHF portion of their tuners having an RF amplifier with a high noise figure?, because other sets in the house were quite happy with that level.

Ordinarily I wouldn't leave an install with <65dBµV at the outlets, however, these were properties I'd not worked on previously, which was the reason for my involvement. The cabling and antenna were otherwise all satisfactory.)

Edit: Clarity.

Edited by M'bozo
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Is that at UHF only?

I ask because I've only seen the problem at UHF (and in the light of DrP's comment.)

Yes it is UHF ,I have no VHF digital in my area

I have often suspected that perhaps a section of the tuner is faulty but with no VHF here ,I have nothing to compare it to .4 potential sites all UHF (some have VHF analog )

I have also had a few problems with Compros like DrP .Once again,no VHF to compare so assumed Compros were crud.

I suspect many retailers have no Idea what their products are like on FTA Digital.

Coffs Harbour Harvey Norman branch have NO FTA antenna available.

All their sets run off a DVD distribution system which makes them all look pretty damn good .

Edited to make a trifle more sense

Edited by bellotv
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