All posts by John Everingham
Below are all of John Everingham's postings, with the most recent are at the bottom of the page.
Mike B: Thanks for your latest comments. here is an update, of sorts. Since the installation retune I have left the TV as it is. BBC1 seems likely to lock the tuner (and remote) but I can get to another channel by switching off ('standby') and selecting the new channel immediately I get a picture on the screen. I will assess the two digiboxes with the old analogue TV on the aerial that has not produced problems. I haven't been able to find a signal quality indicator on the DTV but the Proline box has it, some where... I recall seeing 55% but I can't remember any details of the channel or aerial it was connected to at the time. One of my contacts, south of the Mendips (near Somerton) has the very same problem, especially with BBC1 on her DTV receivers. I may be wasting my time trying to solve the problem at my end. (Just seen John Grogan's post. Perhaps I should relax and wait for things to improve!) I found this page while looking for info on filters... HDTV Antennas and Reception Systems Very sound technical assessment of the issues. The more I worry this 'bone' the more I come up with possible issues and solutions... I'm going to try the 'classic' double sided pcb high pass filter, G8YOM/RSGB. You can find the design here... www.saundrecs.co.uk/g4trn/HiPassFilter.png I've scanned page 199 of 'Amateur Radio Techniques', Pat Hawker, RSGB,1978 edition. I'm going to try moving my aerial to get it a bit further away from my neighbour's. They share the same chimney and I suspect that the lashings have been overlapped. Quite apart from the potential for corrosion between the lashings producing non-linear effects and cross modulation, I believe that the aerials should be isolated from each other. Now that I have put my web page into this discussion my location is traceable so I may as well throw my complete postcode into the mix...BS6 6PD
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Sunday 7 September 2014 3:36PM
Mike B: Thank you for your comments.
It does seem that the BBC channels may be the worst affected, but I'm not sure... they are the ones I view most.
The TV is flat screen, with built in DVD player, from C/PCW (or was it Dixons then?) and the Proline is a digibox from Comet. Not being a tele addict I retained the digibox to feed an old DVD/VCR when I moved the CRT analogue TV to the spare room. It linked through and I could watch DTV on the scart input when the normal aerial input failed. This was not 100% reliable as the digibox tended to lock up too and for reasons I don't understand, this also killed the pass through for the aerial. Perhaps there is a processor controlled buffer/preamp.
The old analogue TV (Grundig, with a scart socket) works fine with a Tosumi digibox (from a charity shop!) and another aerial but the Tosumi digibox won't work on my 'living room' aerial. perhaps this is a strong pointer to needing a higher gain/wider band aerial.
I need to see how the Proline digibox works with the other aerial and TV.
I'm in BS6, close to the railway but the building is tall and the path to Mendip only slightly obstructed by a hill to the south of me. I wondered at first whether it could be a propagation issue due to the hot weather affecting the diffraction over the hill. It could be part of the problem.
I think things may be better following the installation retune but the issue has not been cured by doing it. I plan to change the aerial but I'm puzzled by the lock up issue and may take steps to find out what other signals there are in or close to Band III. (I'm a radio amateur and have a receiver for frequencies up to 1.2 GHz..)
I've checked the bottom of the feeder connections (the center pin is soldered!) and tried several scart leads. I've experimented with an attenuator (a very long, cheap, far eastern extension lead) without noticing any change in behavior. The feeder is new and the aerial is old. I bought an expensive three boom aerial and fitted it, only to get no signal at all. I think, from continuity measurements, that the balun was faulty. It went back for a refund. The new feeder made such a difference in killing the occasional pixilation that I never bothered to get on the roof again. Perhaps I need to!