[smallieboy (OP)]

I have a digital PVR on Freeview in the UK and after about 3 months of everything working OK I started getting interference on reception (usually picture break-up/pixellation). After ruling out aerial/reception problems a TV engineer suggested it may be interference from my DVD player on which the PVR was sat. I got rid of the DVD player and all is fine now.

However, I want to put all my AV kit (i.e., TV, PVR, DVD player, 300-disc CD player, amp and possibly VCR) into a single cabinet but am concerned that the combination of all this equipment (particularly the CD & DVD players) in close proximity will result in loss of picture again.

Firstly, can someone let me know why the DVD would have had this effect and secondly, if it is likely to happen again is there a way of 'protecting' the PVR?

Thanks in advance

[Pumblechook]

Computers and all sorts of domestic electronics can kick out a lot of interference in two ways..  One is from the digital circuitry which can generated lots of 'usually' low level radio carriers modulated to some extent.   The other is from the switch mode power supplies used in most items these days which generates a wideband hash.  It makes using sensitive radio equipment sush as ham radio difficult at times.  Inteference does not usually extend at any great strength into the UHF TV band.  The DVD player must be particularly bad.   I would have thought that if you have a good aerial well away from the DVD player there should be no problems.   Maybe the wideband hash from the DVD PSU is getting into the digital circuitry through close proximity rather than through the aerial.  I would try another DVD player.
 

[LeeE]

If everything worked out without problems for three months before the interference started, then something happened at that point - something changed.  Could range from something breaking (non-catastrophically) to the neighbours relocating something in their house so that it's nearer to your equipment.

Most probable is a screening fault in either your DVD player or in your PVR.

[lyner]

After the 'switchover' you should find a lot fewer problems - the transmitter power will be jacked up by a factor of ten, once they don't have to protect the analogue service.
Rumour has it that they are already inching it up a bit at a time. But don't tell anyone.

[techmind]

...a TV engineer suggested it may be interference from my DVD player on which the PVR was sat. I got rid of the DVD player and all is fine now.

Another possibility is that the DVD player may have a "TV modulator" aerial output (and/or aerial feedthough). This could cause interference especially if the aerial is routed through it, but conceivably even if not. Probably it would only affect one or two multiplexes - unlikely the whole lot.

As a previous commenter posted, you wouldn't expect this to suddenly appear after some months though.

The problem with digital reception however is the "cliff-edge" effect; a certain quality of signal gives you a perfect picture, then the picture deteriorates very rapidly for only a small loss of signal when you're near the critical threshold. In my previous house the TV signals were fairly weak (and the aerial wiring suspect), and in fair weather all was good, but as soon as we got a shower of rain the weakest multiplexes dropped out.

It's also worth checking all the aerial connections are secure. Aerial flyleads are often shoddy quailty and develop bad connections, and the termination of wires on the back of wall-mounted sockets can work loose too. You can also get rodents eating through the cable on the wall!

If you've got a conventional TV aerial then if you unplug the cable from the equipment then measure the "resistance" on the cable/socket to the aerial between the centre of the socket and the outside part using a meter it should be almost a short-circuit (a few ohms, certainly less than 100 ohms). If it's open circuit then there's at least one fault in the wiring.

The DVD player issue might be a pure coincidence (generally moving things around can cause marginal issues to come and go), or it might have just been the straw that broke the camels' back (if it was already marginal).

[smallieboy (OP)]

Thanks for your help everybody.

Just a few comments back - the house is only a 4 years old so hopefully the wiring is OK and the aerial was installed specifically for Freeview last year. The reason I originally got the engineer back was because I thought the antenna may have moved in high winds; in retrospect the reception may have gradually degraded over the three months which prompts the following question -

I've now tried running the DVD player as far away as the various leads will allow and there were no ill effects. Is it likely that any magnets in the DVD/CD players would affect the picture and that this is something that could build up over time?

If this was the case, is there any way of protecting the PVR from the effect?

Thanks again

[lyner]

Look in the D~VD player manual and try changing the modulator channel, like techmind has suggested. It can't do any harm and could sort out your prob.

[Pumblechook]

I didn't think DVD players had modulators?

[lyner]

I have an aging one which I'm pretty sure has an RF out. But it was expensive. The cheaper ones these days probably won't have such a useless appendage.