Digital signal anomaly

  johndrew 11:57 16 Jul 2011

A short while ago I posted with a question with regard to a TV digital box installation link text; all has gone well but I have an anomaly which hopefully someone can clear up for me.

The digital TV suffers from a poor signal on the ITV channels (ITV 1, 4, 5 and the associated +1 offerings) only; all other channels are good; this is from the signal strength indicator which is incorporated into the TV setup menu. As a result I get 'pixelation' (picture break up) on occasion. However, when viewed through the digital box and using the RF loop aerial these channels are perfect with no break up of picture when those through the TV digital receiver are doing so.

The aerial source for both TV and digital box is the same so logically it must be the sensitivity of the equipment fed. Is this a known 'feature' of some equipment, a result of transmission power or a combination of things? Can anyone shed any light on this?

Many thanks in anticipation.

1: http://Another digital changeover question

  gengiscant 12:53 16 Jul 2011

Your link took me here don't see the correlation. LOL.

As for your question I am still having bother since the switch over, I get a worse service now than I did when we had partial digital and analogue. I now get a better picture on my three TV's using an indoor aerial rather than the roof one.

I suppose at some point I might need to replace the outdoor aerial,but at the moment I really do not see much pointI doing so.

  johndrew 13:40 16 Jul 2011

Thanks for coming back.

The link I used was which was the changed to link text using the globe. How it ended up where it did is a mystery to me.

You both confirm my suspicions as the analogue reception on the TV through the same aerial and cables is fine as well. The problem only occurs on digital through the TV. Seems strange that my experience of digital box vs. TV is the reverse of that of fourm member; still that is typical of electronic technology!!

I have checked and changed aerial leads from wall to the various inputs but it has made little difference and given the high strength shown on most channels as opposed to the low on the half dozen or so of ITV perhaps it is not surprising.

Thanks again for the information and confirming my belief.

  octal 14:18 16 Jul 2011

Interesting, from you explanation if I've understood you, you are getting a rubbish reception on some channels, but not others. But you are getting a better signal on the loop antenna.

That is suggesting to me that you are in a fairly high signal area and the signal you are getting from ITV 1, 4, 5 and the associated +1 offerings are coming from the same frequency.

What comes to mind is that the receiver is being overloaded because the antenna gain might be highest on the particular frequency ITV 1, 4, 5 and the associated +1 offerings are being transmitted on.

The solution would be to try and attenuate the signal, I would fit a 6db attenuator to start with and see if that makes a difference. These can be bought from Screwfix, there must be one near you.

  woodchip 17:53 16 Jul 2011

And my suggestion is move the Ariel, relocate it. Is it still pointing in the right direction

  oresome 18:24 16 Jul 2011

Can you confirm that you are feeding the aerial signal first to the set top box and then looping out to the TV which also has it's own digital receiver?

If so, try feeding the aerial directly into the TV to eliminate the possibility of the STB looping arrangement degrading the signal.

  Forum Editor 18:30 16 Jul 2011

Transferred to Digital Home from speakers corner.

  morddwyd 07:03 17 Jul 2011


The digital signal seems to be very unstable in this area (Fife) since changeover.

I live in a fringe area for STV North, and before the changeover I had no problem getting a signal, albeit sometimes a bit pixellated in heavy rain.

Since changeover, when I expected the signal to improve, it's disappeared totally.

I can only assume the stronger signal from the more local transmitters is flooding out the STV North transmitter.

  gengiscant 07:46 17 Jul 2011

'morddwyd' I live in Edinburgh and prior to the switch over,I too had a better signal. Progress, why is it sometimes a step or two backwards?

  johndrew 10:58 17 Jul 2011

Similar to moddwyd I am in a 'fringe' area so a weak signal on some channels may be expected unless everything is from the same transmitter - which it should be as the aerial only points in one direction. There is another transmitter slightly further away but this is at right angles to the aerial direction.


The TV has a connection directly into the digital socket. Using a splitter another connection is supplied to the set top box which is connected to the VCR by SCART. The loop RF is from a further socket on the TV -> DVDR -> VCR -> TV OR I have also tried TV -> set top box -> DVDR -> VCR -> TV the result was the same.

  dms_05 11:50 17 Jul 2011

DSO is a complicated procedure and comes in many stages. The final configuration won't occur until the very final transmitters analogue signal is switched off in 12+ months. Because of overlapping analogue/digital areas we are currently in a hybrid state (in my area we DSO'd 18 months) and some digital Mux's are on reduced power because they will interfere with analogue signals in adjacent areas. So it's likely you will see the position change when the very final final adjustment is made in a year or so. At this point some signals that are on reduced power (10-25%) will be turned on fully and you may find lost signals suddenly reappear.

It's possible in this case that the problem is as above and therefore you are having to attempt to receive more distant transmissions until the final change. I suppose the message is 'don't panic' and wait and see what happens.

It would be very helpful if the DSO people actually explained this in each area as DSO is implemented.

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