DECT Phone causing interference to satellite TV reception.

[Thompson9100]

Originally Posted by SAT-WORLD

Have you made sure that the DECT phone base station,is actually as far a possible from the Sky digibox,not just the handset.

Erm, well, YES.

[Thompson9100]

Sounds like it's worth a go ROBBO. Not sure what cable is in the walls, but I did opt for some, what seemed good quality, twin cable from Maplin. Knowing the developers (no names in case I get done for slander!!!) I guess the stuff in the wall is dead cheap, cos everything else seems to be!

Thanks

[Robbo]

No, sorry, Maplin and quailty are two words that cannot be used together LOL.

Actually they do sell some good quality sat cable, it is a totally ridiculous price of £1.59 a metre (FT100). Less the 50p a metre is wf100 on ebay.

[Avril]

I have DECT 2 phones and answer machine cant say I have noticed any probs and they are in same room as satellite TV receiver.

[TheCoder]

Still not convinced that they can actually interfere with each other because of the digital nature of the signal and the difference in modulation methods used. The simplest of signal processing could recover both digital signals even if they were completely mixed.

The more I think about it the more I think the only way a DECT phone could interfere with a Sky box is if the interference were getting onto the Scart and/or TV connection. As the signal is effectively analog at that point then it could be relatively simply interfered with and you could end up with all kinds of artifacts.

Pure digital interference is fairly unique in appearence in that you basically get Mpeg dropout and block pixelation. Any kind of fuzzyness is not caused in the digital path - its a purely analog phenonoma. Ghosting is also very unlikely with digital in that any significantly delayed reflection of sufficient power to be "received" would stuff the mpeg decoding process and cause complete signal dropout rather than mere interference.

[Robbo]

Well, the fact of the matter is that people have experienced this effect on tps that have an IF frequency fallng in the DECT band, with switchong off the the DECT system curing the problem.



Not experienced it myself either to be honest, and I have 4 DECT phones + base.

Apart from that the modulation types etc are not that important, if the carrier level is larger on an interfering signal it will block the wanted signal.

[pedro2000uk]

Originally Posted by TheCoder

................


Any kind of fuzzyness is not caused in the digital path - its a purely analog phenonoma. ..................

Not so...

Read up on lossy... then take another look at digital 1s & 0s .. they aren't the same 1s & 0s that started out and can change at any & every digital processing stage especially on gear that says HD but x y z shortcuts have been used to do it all cheaper so it's only anything like HD when the frames are still long enough ..... and any of that can be helped or hindered by good/ bad signal to noise etc.. as any processor stage tries to 'process' a dirty stream but not to the breakup blockies - just runs out of processing time so in kicks shortcuts -

[andyjill]

I had sky for about seven years and never had any problems, I'm at my mum’s house in Great Yarmouth and had a thunder storm, all sky channels went off, they say it happens every time they have a storm or even just rain, any idea's why this happens?

[TheCoder]

Originally Posted by pedro2000uk

Not so...

Read up on lossy... then take another look at digital 1s & 0s .. they aren't the same 1s & 0s that started out and can change at any & every digital processing stage especially on gear that says HD but x y z shortcuts have been used to do it all cheaper so it's only anything like HD when the frames are still long enough ..... and any of that can be helped or hindered by good/ bad signal to noise etc.. as any processor stage tries to 'process' a dirty stream but not to the breakup blockies - just runs out of processing time so in kicks shortcuts -

Regardless of the "1's & 0's" the end stage processing is the Mpeg phase. If you have bad data then then you lose an mpeg segment. As I say, you never get fuzzyness - thats a uniquely analogue artifdact !

With digital, the signal is either there or it isn't. There's really no halfway stage. If its there then you get a picture, if it isn'y you may get little coloured blocks as the mpeg tries to build a picture from incorrect data. You could, of course, also lose Mpeg decode completely (if the data corruption is really bad enough) in which case you get a black screen.

What you say above is sort of correct. Yes, you can end up with incorrect interpretation of the original data so you may interpret a 1 as a 0 or vice-versa. Even with all the error correction you can still end up wih bad data BUT that bad data will be digital when it comes out of the decoders AND the box will definately know its bad data so will simply dump the full TS packet (Each packet is fully checksummed and all boxes will check for correct checksums - its past of the DVB standard that they do so). Bad data never gets as far as the Mpeg decoder to start with !

If there's not enough Mpeg data to fully construct a frame then the box will do the best it can usually by filling with runs of a single value (thats usally why Mpeg dopouts are little green squares).

There's simply no room for fuzzyness in a digital process !

So, back to what I said earlier, if fuzzness is occuring inside a box then its because a signal is somehow getting into the analog section of the box and interfering AFTER the mpeg frames are built. That would tend to indicate signal ingress either on the scart lead or possibly the Aerial out sockets to your TV. It is quite possible, for instance, to get fuzziness if you connect to your TV via the Aerial out and your chosen output frequency co-incides with one of the terrestrial analog channels.

[pedro2000uk]

Originally Posted by TheCoder

Regardless of the "1's & 0's" the end stage processing is the Mpeg phase. If you have bad data then then you lose an mpeg segment. As I say, you never get fuzzyness - thats a uniquely analogue artifdact !

..........

You have to look at it from a manufacturer's point of view ... especially using the cheapest chips to still get a product to market & stick HD on it.... it is not a perfect 1's & 0's world and HD or any digital gear is made for a price ..

are you a programmer .. ?