All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Andy K: The FOXSAT-HD box is a satellite-only box. You can't use it with terrestrial broadcasts like Freeview and Saorview.
A conventional Freeview box sold in the UK won't work with RT 2 HD transmissions, because they generally don't support MPEG-4 AVC. A Freeview HD box would work as it does support MPEG-2 and MPEG-4 AVC.
Saorsat will be carried on the Eutelsat KA-SAT satellite, orbiting at 9°E - a long way from the Astra 2 cluster at 28.2°E. You will need a separate dish for this service.
You should be able to use the FOXSAT-HD to watch Saorsat channels, as it claims to support the mode used, and you should be able to connect both dishes to the box via a software-controlled switch, as it supports DiSEqC. It may even support a motorized dish as the manual claims it supports USALS, one method of positioning the dish, though I think separate dishes would be cheaper than a motorized dish.
The manual is a bit sparse on detail of how exactly to set up multiple dishes, though.
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Daniel Peake: Have you just moved in the last week?
The last Scottish analogue transmissions were switched off last Wednesday morning. You will need to do a full retune on your TV if you haven't already. It might be called Full Reset, Default Setting, or First-Time Installation, and it might be under the Software Update menu rather than the tuning menu. Add Channels is not enough, you need it to completely remove everything it previously knew about where the channels were.
TV Re-tune may have a guide for retuning your TV, or a copy of the manual.
It's possible that your TV cannot handle the 8K mode used for post-switchover transmissions. Check whether it's on the list at http://www.digitaluk.co.uk/2kequipment , and check with Philips whether any software/firmware updates are available.
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Michael: Whether you are affected will depend on exactly where the 4G transmitters end up being sited, and how powerful they are (how large an area they are intended to service), and the aerial group and polarization of your target transmitter.
The problem that will occur will be intermodulation, which is caused by having too much signal overall. Transmitting the 4G signals in a band that many aerials are *designed* to pick up well (Groups C/D, E and Wideband) means that, when the 4G signal is added to the TV transmissions, it could cause distortion in amplifiers and/or in the receiver's front end (which contains an amplifier). That distortion results in frequency-shifted copies of each transmission appearing as well as the original, which when added together, result in too many errors to be automatically corrected.
If you are using a transmitter that uses horizontal polarization, which most of the main transmitters do, you are less likely to be affected, as the 4G transmitters are expected to be using vertical polarization. Aerials pick up much less signal from the opposite polarization (Digital UK's predictor conservatively assumes 16 dB less, about 40x, most real aerials are better though it varies across the frequency range).
Vertically-polarized aerials generally have a wide acceptance angle in the horizontal plane, that is, signals arriving to the side of the aerial. If you're using a relay, you're more likely to be affected.
People using a transmitter that transmits in Group A or Group B should use a Group A or Group B aerial. In Group A the gain for a grouped aerial is far better than a wideband, for the same size aerial. If your transmitter uses Group A *and* Group B, a semi-wideband Group K covers both groups but cuts off well before reaching the 4G frequencies. Often Group K aerials are sold as Group B or Group B/K.
If you start to have problems after 4G services start up, the first step would be to remove any amplifiers you have, or turn them down, depending on whether the intermodulation is happening in the booster or in the receiver itself. If that doesn't help, add an attenuator to reduce signal levels.
I suspect Ofcom are saying that filters may not help if your transmitter uses C60, because filters steep enough to cut off all of C61 while avoiding C60 would need to have many tuned elements and are likely to be expensive. You would only need a filter if the received signal strength from the 4G transmitter was substantially higher than from the TV transmitter. With the clearance programme still in the early stages of planning, it's hard to say exactly who would be affected.
I do think their 30,000 homes is likely to be an underestimate, due to the overuse of extra-high-gain wideband aerials (frequently where a smaller grouped aerial would have delivered more gain, and where high gain wasn't even necessary) and viewers' tendency to add a booster when any reception problem occurs.
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Michael: I see from your previous posts that you're using Waltham. This is mostly a Group C/D transmitter but SDN will be transmitted down at C29, Group A, so you do need a wideband aerial. When the transmitter switches over at the end of August, I would recommend removing any boosters at that point.
Digital UK's trade predictor already shows a prediction of 100% across all six multiplexes, so you're likely to have problems with too much signal at switchover if you do have a booster, or a high gain aerial.
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Justin MacNeil: Each device usually adds a small amount of amplification to offset the insertion loss of the device itself, and sometimes a little more to offset the expected loss in the cable. That amplification adds additional noise, which can cause problems. Also, each amplifier could be overloaded, introducing distortion, and cause intermodulation problems, or the level could be too high when it reaches the final device in the chain, again causing intermodulation.
If the device doesn't actually tune into the signal from the aerial, and you're not using the RF modulation feature, it's better not to include it in the chain. I have to admit I've not heard of Blu-Ray players with an RF modulator before!
You also need to check that any devices with an RF modulator are set to use a free channel. You should avoid using any channel that is 1, 5 or 9 channels above any transmissions that you want to receive. (N+5 and N+9 cause beating problems, while RF modulators commonly don't suppress the lower side-band as real TV transmitters do, which then ends up on top of the channel below.).
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John Child: The BBC recently changed their HD transmissions to use a new mode. Try unplugging your Freesat receiver for 10 minutes, and plugging it back in. If that doesn't help, see if there is a Retune option somewhere in the menus.
Receivers are supposed to pick up the changes from the information carried on the Freesat EPG transmissions, but they don't all seem to be doing this properly.
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Dee: In this particular case, the Sandale transmitter and its coverage area should no longer be shown, as it no longer broadcasts TV signals. It was formerly used for the BBC's Scottish service.
ukfree.tv was originally designed for pre-switchover Freeview and very few of the relays show up. As far as the prediction system here goes - which doesn't have as much detail as Digital UK's - Haltwhistle only covers a couple of pixels and they're all predicted to be served better by something else. A particular weakness of this site's system is that the terrain data is very coarse, so it can't tell that - in this case - Cold Fell is blocking reception from Caldbeck.
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Mike Gallimore: Digital UK's predictions are the exact opposite of what you're saying. The prediction is for extremely good chance of reliable reception from Mendip, but poor or variable for Hannington (South) and Stockland Hill (South West).
This tends to indicate that signal levels are too high overall. If there's a separate amplifier included in the chain before the distribution amplifier, remove or bypass it. If not, or that doesn't help, turn down the distribution amplifier, and/or add an attenuator between the aerial and the distribution amp.
If the distribution amplifier is separate from the splitter, remove the amplifier. If not, consider replacing the distribution amp with a passive (unpowered, unamplified) splitter.
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Phil Harwood: There is a fault shown on the Marlborough transmitter page on Sunday between 1:44pm and 4:46pm. It's possible that the problem occurred earlier and the BBC only found out about it at 1:44pm.
No maintenance work is currently happening at Hannington, as far as we know. Nothing was planned for last week and nothing is planned for this week.
We need a full postcode to identify which transmitter you might be using, and what the problem might be.
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Wednesday 29 June 2011 1:19PM
Den: The satellite footprint diagrams for the Astra 1 cluster at 19.2°E show a 60cm dish should be enough. Go to Satellite Fleet - SES ASTRA and click on the satelites in the 19.2°E column.
Any free-to-air receiver will be able to display any channels transmitted free-to-air. See Astra 1H/1KR/1L/1M/2C at 19.2°E - LyngSat for the list. A UK Freesat receiver should do the job, you will need to use the Other Channels feature to tune in the services you want. If equipped with the DiSEqC feature, you can hook up a DiSEqC switch and connect dishes for both the Astra 1 cluster, and the Astra 2 cluster at 28.2°E which carries the UK channels.
If you only want the German, Austrian and Swiss channels, other free-to-air (non-Freesat-branded) receivers are available, or some Freesat receivers have a non-Freesat mode.