All posts by Jim F
Below are all of Jim F's postings, with the most recent are at the bottom of the page.
James: Your new Toshiba recorder might not be working correctly - a few brand new TVs or digiboxes are insensitive, typically on the higher frequency channels. MUX D at Guildford is the highest frequency (UHF channel 54), so it looks like a duff box to me.
If you take it back, make sure you aren't fobbed off by being shown it working on a massive signal - as Dale says, you could make it work with an amplifier, but you shouldn't need to.
My suggestion is to get a replacement.
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Hi Tony: Analong (Annalong?) would be a much better location for receiving telly from Beary Peark. The radiation pattern seems to give full power in your direction (the Port St. Mary Tx puts out very little your way).
It does appear that you are exploring the tolerance of transmission formats to co-channel interference. Trouble is that there are a lot of contenders for co-channel signals on 43, 46 and 50:
Chatton (more northerly than Beary Peark),
Emley Moor (slightly south of BP),
Llanddona (on Anglesey, south-east),
and Sutton Coldfield (analogue, almost in line behind Llanddona).
From your comment about getting best results with the aerial pointing slightly north of BP, I'd suspect Emley Moor.
A very directional aerial might improve the situation - probably need to have a narrower beamwidth than a single log periodic by using two horizontally spaced logs and a phase matched combiner (Vision Stealth kind of arrangement).
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Nick: Transmitter engineering info for Crystal Palace says "very weak signal from 12:58 yesterday to 13:40 yesterday" for HD.
Suspect that this may be the cause of your signal loss, but their information implies that it should be back today.
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Dawn: Y splitters can give trouble, but you can check it by swapping the two output feeds over. If that makes the bedrooms stop working and downstairs is now OK, its the Y splitter.
Otherwise, shorts in the coax feed to downstairs is likely - coax plugs with tiny screws holidng the centre core are frequently the cause of this, when the screws become loose.
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Briantist: It looks like it makes sense if you lose those "-" signs you've put in front of the field strength numbers i.e. shaded area is 58dBV/m and thick line is 65dBV/m (the thick line being closer to the transmitter and hence having higher power).
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Julie: There are filters available for reducing e.g. taxi interference - "Google TVI filter" to see what the simple ones are like. For proper filtering, Vision make a V25-101.
There's a complication though for your setup - the filter needs to go between the aerial and any amplifier (to prevent input overload and subsequent distortion in the amp). With your SLx aerial, you can't insert the filter in the correct location, and adding the filter after the amplifier won't work (amplifier will still overload).
You could consider a non-amplifier set-top aerial (e.g. Telecam TCE2000) connected to a filter and then have a separate amplifier.
I've yet to see an amplified set-top aerial that incorporated a decent filter.
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Ann Lynn: Your distribution amplifier in the loft might be the cause of your trouble (usually the power supply becomes noisy due to failure of smoothing capacitors, which injects mains hum onto all outputs).
You could check this by removing just one output cable and see which telly has "gone off" completely.
Now disconnect the coax input from the amplifier and join it to the first cable you've unplugged (you may need a coax "joiner").
See whether the one telly fed by this coax appears to be any better. If it is, then your amp is duff.
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Brian: As KMJ,Derby says, it looks like interference. You're very close to the Leamington Spa relay which has BBC1 analogue on Ch56 and you're in the maximum transmission direction, so probably have adjacent channel interference at the moment.
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jame hore: many of the failures like yours are caused by a dodgy coax cable from the wall socket to the TV set (especially if the TV is wall mounted and the coax cable has a tight bend close to the connector).
Try a different coax cable and see if that helps.
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Saturday 2 July 2011 4:48PM
Tony Mallon: Newry (as in Armagh?) could be receiving UHF Ch.50 from Presely, but this would be H-pol.
RTE from 3 Rock is also H-pol (though why you'd be using 3 Rock rather than the V-pol Clermont Carn Tx isn't clear).
The SD channels from Presely are also on UHF 43 & 46, so are using the same frequencies as Beary Park, but so are several other relays on the IOM (Port St. Mary, Union Mills, Laxey, Ramsey, Jurby. All V-pol. apart from Ramsey).
Would it be any better if you tried an H-pol aerial pointing at Presely?