All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Pedro dd: The terrain data here is too coarse to be useful. I use Terrain - shows radio profile between two UK sites to optimise you DTT, Freeview, DAB or analogue TV reception . That's still only accurate to 0.5km.
The terrain data at Wolfbane UK digital TV reception predictor is smoother but I'm not sure if it's more accurate, and you need a PostScript viewer to view it. I use RoPS from The RoPS PostScript Viewer but usually don't bother with Wolfbane since finding Megalithia's terrain data.
Do not pay any attention to the signal strength information or aerial recommendations from Wolfbane. There's some error in the calculations that makes the calculated voltages around 80 times smaller (38 dB) than they should be. (RG47SH)
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M
Can I use my ex-contract sky digital satellite receiver to get Tuesday 5 April 2011 11:28PM
Reading
Rob: Normally Sky distribution is done through analogue TV signals, and you tune it in as if it were an analogue TV station. You would normally select a different mode, source or input using the TV remote (terms vary between manufacturers) to watch Freeview rather than analogue TV.
It looks like the DigiSender uses a SCART connection. SCART has a pin that the device can use to tell the TV that it's on. If this pin changes from off to on, the TV automatically switches to the device. If it's on when the TV is turned on, it may also automatically switch to the device. Again, by pressing the INPUT, SOURCE, TV/AV button or similar on the remote, you can get back to Digital TV.
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peter: I believe I saw a message yesterday on Digital UK's Planned Engineering Works website saying that the transmitter was going to be off between 10:30am and 4:30pm.
Digital UK - Planned Engineering Works
That seems to be the only place that works are announced, and it's usually with very short notice. (RG47SH)
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blackfish: The BBC A multiplex at Nottingham is already at full power. D3&4 and HD services will start up at full power next Wednesday. The commercial multiplexes stay on low power until 28 September.
If you couldn't get Nottingham's analogue signals with reasonable quality, digital is likely to be erratic. I'd stick with Waltham.
A full postcode would allow us to give more information.
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Annie: It looks like the best bet at that location is the Sheffield (Crosspool) transmitter. To get all services using this transmitter, you would need a wideband aerial. If Channel 5 analogue is clear, you probably already have a wideband - Sheffield was originally a Group A transmitter (channels 21-35) but C5 was added right at the other end of the UHF band at C67.
If C5 is very snowy or doesn't work, that probably explains why you don't get digital signals now. They're transmitted at the upper end of the band, and require a wideband aerial. You're currently predicted to get excellent results on the BBC channels and on ITV1/ITV1+1/ITV2/C4/C4+1/More4/E4/C5, variable results on Multiplex A and poor results on the other two multiplexes, if you have the right aerial.
If you don't change the aerial, the public service multiplexes (BBC channels and ITV/C4/C5 channels listed above) will work, but the commercial multiplexes won't.
The aerial can be changed without replacing the cable, but it's recommended to do both. The cable normally used for installations before the mid-90s had very little screening and it's likely to pick up electrical noise. On analogue this just causes a bright patch on one line - on digital it causes break-up for several seconds. Also, cable that's been outside for a while tends to deteriorate with exposure to sunlight - the insulation weakends and it starts to let moisture in.
The cable inside the house is less likely to be damaged, so it could be spliced with a new external run, but is still likely to pick up more noise than a new cable would.
I know of a few installers in the Sheffield area. Perhaps you could try A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. or Wright's Aerials (RG47SH)
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ken picton: Yes, probably they will improve. Pick TV (channel 11) is on the SDN multiplex and 5* (channel 30) is on ArqA. These multiplexes are currently running on low power and channels with more interference. They will reach final channels and full power on the 27th.
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Sandy Heath (Central Bedfordshire, England) Full Freeview transWednesday 6 April 2011 9:16AM
Reading
Duncan: The pre-switchover digital transmissions are all outside Group A - above C38.
There are really a few possibilities. Either you've had a wideband all this time and not known it, some part of the aerial is missing making it pick up outside the designed channel range, or you're close enough to the transmitter that it actually doesn't matter.
If you're getting all the Freeview channels already, you should still be able to get them all after switchover completes.
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2011 switchover week two: The Wrekin and Ridge Hill transmitterWednesday 6 April 2011 12:54PM
Reading
RS: For people who already have Freeview, multiplex 1 is turned off and BBC A starts up in place of BBC Two analogue (usually, though at some sites it uses a different frequency and whatever channel was using that frequency replaces BBC Two).
It's recommended that you do a full reset on DSO days, because some information could still be cached.
If you want to try a manual retune, delete the following:
1 BBC ONE
2 BBC TWO
7 BBC THREE
9 BBC FOUR
70 CBBC Channel
71 CBeebies
80 BBC NEWS
81 BBC Parliament
105 BBC Red Button
301 301
700 BBC Radio 1
701 BBC R1X
702 BBC Radio 2
703 BBC Radio 3
704 BBC Radio 4
705 BBC R5L
706 BBC R5SX
707 BBC 6 Music
708 BBC Radio 4 Ex
709 BBC Asian Net.
710 BBC World Sv.
(This is the content of the BBC A mux post-DSO. Some are still on Mux B until the 20th.)
Then do a manual scan on the frequency for BBC A. At Ridge Hill this is C28, 530 MHz.
For other thoughts on avoiding Welsh services, see Digital Region Overlap.
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Alan T: 'Normal' inversion problems (tropospheric enhancement, single bounce off the atmosphere) usually occur at night as the atmosphere cools. Tropospheric ducting (multiple bounces between layers in the atmosphere, travelling much further) requires specific weather conditions: you can see a forecast at Tropospheric Ducting Forecast for VHF & UHF Radio & TV . No ducting has been forecast over Rugby for the last week, though it was close on Saturday (see past week forecasts at the bottom of the page).
Sandy Heath has no channels in common with Sutton Coldfield at present. The commercial multiplexes' changes to their final channels and power levels are delayed, so while ArqA has been allocated C52, it won't get there until November, after Sutton Coldfield has stopped using it (and Tacolneston has stopped using it for C5 analogue). Likewise, Nottingham has been allocated that channel but won't get there until September.
I think it's much more likely that your problem is too much signal, and Mux B and C are clobbering each other, because they're on adjacent channels. An adjacent analogue channel seems to do much less harm, because most of the power is concentrated in the carrier sync pulses which have very narrow bandwidth.
How can it be too much signal with the box only showing 5/10 signal strength? Simply, that the meters are not calibrated to sensible levels. On my box 100% appears to be 95 dBuV, 35 dB greater than the maximum recommended level, or 56 times what it should be! 0% is 35 dBuV, about the minimum that could possibly work - at least an extra 10 dB is recommended to allow for normal signal variation.
I'd suggest removing any amplifiers you might have, and adding an attenuator if that doesn't help. (RG47SH)
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Tuesday 5 April 2011 11:13PM
Steve Freear: For thoughts on how to get the best out of a loft aerial, see http://www.wrightsaerials.tv/articles/whatsat-201007.pdf (RG47SH)