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BillybobBanjo
Beginner
589 Views
Message 1 of 7

DTR-DTR4000 inferior sensitivity, no freeview channels found

Is the new DTR-T4000 box I have received faulty? It finds no freeview channels at all. This is when my four year old Sony Bravia shows a signal strength of 80 + and a signal quality of 75+. There was no problem with the previous DTR-T2100 box I had which worked perfectly.  I have a loft aerial with a signal booster in line which has worked fine for many years. 

The box did briefly find some channels which were unwatchable. BBC1 - Signal strength 100, quality 0.

Why should this be when the TV works fine, and that's when the signal has passed through the BT box!

Very frustrating.

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6 REPLIES 6
TimCurtis
Guru
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Message 2 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

@BillybobBanjo 

It's possible that the signal strength is too high & overloading the tuners as thgey are very sensitive. The 100% signal strength you did manage to get might be the clue.

Try removing the signal booster or if it's variable dial it back a bit. On the Youview boxes a signal strength of around the 90% is a good target figure, obviously with 100% signal quality.

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BillybobBanjo
Beginner
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Message 3 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

Thanks for your reply.

I have since found threads that suggest using a 6dB attenuator with good results, so I have ordered one. In the meantime I shall follow your suggestion and get in the loft and turn the aerial amp gain down and see what happens. All seems a bit counterintuitive when there is zero signal quality right now.

Cheers.

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Keith_Beddoe
Distinguished Sage
Distinguished Sage
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Message 4 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

To recover and record the digital signal, the decoder has to see clean signal level transitions, as there is no form of automatic gain control like there is on a TV which is designed to work over a very large signal range, and can tolerate quite a few errors before the picture breaks up.

If the signal is showing 100%, then there is a fairly good chance that its actually over 100% all of the time, and the signal transitions are not going to be  seen by the decoder, so the quality of the decoded signal is going to be zero.

Because the input decoder has a wide bandwidth to enable it to receive all of the multiplexes, it only takes one multiplex to be too strong, for the decoder to  fail to work properly.

There have been lots of similar posts on this forum, about this issue, and the solutions involve either turning down or removing any amplifiers, or inserting a variable attenuator.

BillybobBanjo
Beginner
548 Views
Message 5 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

Update:

If I wind back the aerial amp gain I lose signal strength very quickly still with no improvement to signal quality. Still with the the gain fully wound up with a bit of refreshing the connections I managed to get 20% signal quality - not enough for a reliable picture on BBC1. But now the TV settings show 93% signal strength and 100% signal quality and still receives all channels perfectly?

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BillybobBanjo
Beginner
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Message 6 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

Thanks for your post.

So it sounds like if I tune the aerial system so that the TV box accepts the signal levels, the TV may no longer accept that signal level?

Why does the new improved box not work when the old DTR-T2100 worked just fine?

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BillybobBanjo
Beginner
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Message 7 of 7

Re: DTR-DTR4000 inferior sensitivity, no freeview channels found

Problem solved.

After remaking coaxial connections in the loft and adjusting the aerial amp gain to no avail I found that there was a problem with aerial lead just as it enters the TV box behind the coax connector. I can only assume there was a high resistance break in the lead which allowed enough signal for the TV but not enough for the BT TV box. I cut back the cable and fitted a new connector and all is now working perfectly. Now 94% signal strength, 100% signal quality (BBC 1 HD) and no attenuator required.

Thanks for your input.

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