All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Mart G: See Compare Freeview and Freesat TV | ukfree.tv - independent free digital TV advice for the difference between the Freesat and Freeview line-ups.
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Mart G: I should have added, make sure you do a full retune - first time installation, default setting, full reset, 'virgin mode', reinstall all channels, it's called different things by different manufacturers - as many receivers won't pick up a change to a different frequency when you just use 'add channels'. See TV Re-tune for some product manuals and retune guides, or check the manufacturer's support site.
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Thomas: I agree that it's not likely to be another transmitter, C47 wasn't often used for BBC One, the map at UK TV Frequency map - channel C47 (682.0MHz) before switchover map | ukfree.tv - independent free digital TV advice shows only Holywell, near Liverpool, and The Bournes, south of Aldershot. Both are very low-power relays on vertical polarization.
The transmitters are not perfect and do produce some intermodulation products outside the allocated channel. The out-of-channel emissions are filtered off within the channel combining unit, but these filters are only as good as they need to be to stop too much interference being broadcast or power being fed back into another transmitter. If you're close enough, you certainly could have been watching a little intermodulation.
The digital transmitter manufacturer claims that out-of-channel output should be less than 40 dB below peak level (or 0.01% of peak power). Arqiva's filter specification is an additional 18 dB (1.6%) in the adjacent channel, 43 dB two channels away.
Sources: http://www.actuonda.com/p….pdf p20, http://www.arqiva.com/cor….pdf p23.
You can see what 44 dB less signal gets you at Comparison of signal quality with reducing signal level - the bottom picture is 44 dB lower than the top. There's still a degree of colour in there, and given your location I suspect your analogue levels are over 60 dBuV already.
Digital only requires about 20 dB of signal-to-noise ratio to receive reliably, so I don't think this interference generated within the transmitter itself is likely to be a significant problem - certainly if you never noticed it on analogue.
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john: New satellite-grade - dense copper braid over copper foil outer conductor - cables should sort out pick-up of electrical noise.
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Paul Kelly: *Just* Russia Today, or also all other channels on Multiplex D (see above)?
Mux D on C55 is out-of-group and subject to more interference than the others because Winter Hill ArqB also uses C55. Depending on the weather conditions, the effect of this co-channel interference could be greater or lesser on a particular day. The effect does depend on where you are - people particularly affected will be those whose aerials point in that direction or who are in the north-west of Sutton Coldfield's coverage area.
This channel clash goes away in two weeks, and all post-DSO transmissions from Sutton Coldfield are within group.
If it is just that one channel, your box might have trouble with a large NIT - see http://www.digitaluk.co.u…tnit for a partial list - or not have enough memory. If you have a number of channels in the 800s, or other duplicates elsewhere in the channel list, try doing a full reset with the aerial unplugged and then manually retune using the channel numbers above - the middle line, except for BBC A on C43, and Mux A has moved from C47 to C41 for the next two weeks.
The current low-power HD transmissions are actually from Lichfield, which also transmits analogue Channel 5. It's referred to as being from Sutton Coldfield in many sources, as the transmitters are so close together and supposed to serve roughly the same area. For people very close, though, they may not be close enough together for the aerial to pick up both well enough.
High-power post-DSO HD transmissions will come from Sutton Coldfield; they start at stage 2 on the 21st. If analogue BBC Two is currently good quality you shouldn't have any trouble.
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Alan: Time to try the small claims court, I think. They're still a supplier acting in sales to the public.
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allen: You haven't said where you are. The high-power HD services start at the second stage of switch-over, on the 21st. They are transmitted from all relay transmitters as well as main ones, and have equivalent coverage areas to the SD versions of BBC channels and ITV1/C4/C5.
There are 'early' HD services in the Birmingham area, from the Lichfield mast rather than Sutton Coldfield, and also from the Emley Moor tower in west Yorkshire, which have been running since the middle of last year. I believe these have restricted coverage compared to the other multiplexes, and they're on lower power.
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Pensioner 69: I'm assuming you mean an old video cassette recorder (VCR). Analogue is now being switched off completely - analogue BBC Two no longer broadcasts from Sutton Coldfield. The other analogue channels will go on the 21st. Channel 5 should still be around for the next two weeks, but was always more difficult to receive as it broadcasts on a low channel from the Lichfield mast.
To record digital TV programmes other than the one you're watching, you need to add a Freeview box to decode the signal for the VCR, and set the VCR up to record from that - this would probably be AV2 on the VCR. It is a lot easier to get a hard disk-based recorder, generally called a Personal Video Recorder (PVR).
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KayPot: yes, treat the TV the same as a separate Freeview box. Essentially the TV just has the Freeview equipment as an internal component.
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Wednesday 7 September 2011 1:22PM
Will: HD services start at the *second* stage of switchover, on the 21st.