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Hi Simon, One thing we've noticed from our Freeview installation with loft aerial is that the signal strength weakens considerably in wet weather, opening the door for more interference. This is due to the greater conductivity of roof tiles, nearby trees etc, when wet. Have you noticed more interference in wet conditions, or is it an all-weather occurrence? Admittedly, people don't tend to mow their lawns when it's raining, but it's worth keeping a lookout. Regards etc, Ray Knowles. >---- Original Message---- >From: simon@xxxxxxxxxxxxxx >Date: 02/03/2013 19:37 >To: <list@xxxxxxxxxxxxx> >Subj: [LUG] OT: Freeview interference > >Okay totally off topic but I know the crowd here, and you've had several >years now to get experience with Digital TV since I last pondered this one. > >Have been given ultimatum by her who must be obeyed to sort the >interference on the TV. > >This is some sort of impulse interference mostly caused by motorbikes >and lawn mowers, but also a couple of things we can't pin down but >almost certainly something the neighbours do, since we've powered off >everything in the house in a previous troubleshooting effort including >heating, freezers, computers, WiFi, mobiles and the like. Mostly it is >short lived, but can last longer and lead to upset small boy (or woman). > >Two options spring to mind. > >1) Outsource it e. g. professional Freesat installation. > >2) Figure out where the signal is picked up and sort it. > >I figured (2) was worth a punt, since it is probably going to be a lot >cheaper, and the nightmare scenario of doing (1) and still getting the >interference has to be considered. > >The aerial and cabling hasn't been touched since the previous owners set >it up for analogue TV. > >Layout is: > >Loft mounted aerial. Not ideal but I don't want to remount it externally >if I can avoid it, and the signal is clearly good enough 99% of the time. > >Passive UHF filter (unshielded). I assume this is a bandpass filter, box >strapped to a rafter just below the aerial, no power, simple circuit >board no shielding at all (well plastic case which is in poor repair). >Doesn't look like a clever design to me, but makes sense given the >presence of an amplifier for it to have been added. > >UHF Booster/UHF splitter. White unlabelled boxes clearly bought as a >set. Suspect this was the previous owner adding TV point in the kitchen >as the install is different quality to the other cabling work which is >all fixed down to rafters. > >Booster had two leads out of it till this afternoon, one was feeding >some wallplates we don't use. Disconnecting the spare lead doesn't >appear to have resolved the issue. > >~10m cable run to wallplate. > >Wallplate. The wallplate whilst using the simple unshielded connectors >is in a galvanized steel box, and the front plate is also metal > (presumably steel with brass effect finish to match the others). So I'm >guessing it isn't the weak point in the shielding that various websites >suggested it can often be, but hard to be confident. > >Fly lead to Digibox. > >Fly lead and SCART to TV. > >The online advice I've found is nearly all cribbed from the same >original source. It all contains the phrase - "This problem is more >common with loft aerials than rooftop aerials." - which gives away a >common origin. I suspect it was written by a guy selling high quality >co-axial cable as his site recommends buying higher quality co-axial >cable from himself, which may not be a bad idea. > >Questions: > >Anyone experienced similar and sorted it with terrestrial Digital? I'm >wondering if it is pretty much inevitable with the technology in use. > >My guess for weak spots are: > >a) Antenna (being in roof) >b) The Passive UHF filter before the amplifier because it is unshielded. >c) The Digibox itself - cheap one from Tesco on the expectation HD >digiboxes would arrive soon when purchased. It is too light to have much >if any shielding internally and the case is plastic. >d) Cables > >Which would folk address first? > >Is their a diplomatic way to ask to borrow your neighbour's petrol >driven lawn mower for testing? Or a good way of impersonating a noisy >petrol engine. As it is one of the few predictable ways of generating >the interference. > >Has specification of boosters and UHF bandpass filters changes for >Digital TV? > >Should I also be concerned with noisy mains? > >Anything else I should try first? > >The galvanised wallplate has an earthing point on it, but no earth is >attached. I imagine this is not an uncommon state of affairs. I can't >see it should matter, and I don't have a convenient real earth. Is this >a problem? > > >Costings > >Replacement passive filter with shielding is about Â10 and easy to do. > >New satellite quality cable is only slightly more but given the current >cable has no slack, I suspect it will be a pain to thread through, but I >might be wrong on that. > >Digibox I was thinking put it in a metal biscuit tin as and when the >problem occurs. Just have to find a biscuit manufacturer still supplying >proper tins. Would this likely shield it enough if it is the problem? > >Aerial - I think I'd go with Freesat before trying to move this outside >or replace it, since the price difference is going to be negligible. > > >-- >The Mailing List for the Devon & Cornwall LUG >http://mailman.dclug.org.uk/listinfo/list>FAQ: http://www.dcglug.org.uk/listfaq > -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq