All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
ren: Make sure your mobile phone isn't near the meter, aerial or cables? Widebands don't have a very sharp cutoff at the upper end, and the phone frequencies at 880-914 MHz aren't that far away from C68 at 850 MHz. 880 MHz would be about channel 72 if it were a TV channel.
The exact uplink frequency used by the phone would depend on what channels are allocated to the neighbouring base stations and the channel the base station picks for the phone, so it might well only occur at some sites.
Phones are allowed to emit up to 2 watts - more than enough to swamp the more distant TV transmissions. Many relay transmitters only emit a couple of watts, but cover half a mile or more!
Some people also have trouble with TETRA radio, used by the emergency services, at around 400 MHz. Filters are available.
Since Mendip and Oxford are Group C/D transmitters, you may find yourself fitting filters when the proposed 4G 800MHz base stations start up (taking channels 61-68).
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David: Yes, the transponder uses DVB-S2 rather than the original DVB-S. DVB-S2 generally gives more capacity per transponder with the same robustness, or more robustness for the same bitrate.
TVs with Freesat logos are supposed to support DVB-S2 as well as DVB-S, as it was widely expected that HD transmissions would soon go to DVB-S2 transponders, due to the extra capacity.
The manual for your TV does claim it supports DVB-S2. I don't think it's likely that this is your problem. It's more likely to be a dish alignment issue - 4hd is on a different satellite position from the rest of the cluster, and that satellite uses the same frequencies for both polarizations, unlike the Astra satellites where they're staggered and less likely to interfere with each other if the polarization is a bit off.
See DaveCheltenham's reply above for information about skew problems.
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Dave: your TV may be confused by the data appearing on both the high-power BBC A multiplex and on the low-power Multiplex B. However, my understanding was that they were carrying it on both Mux 1 and B before switchover. There are stories that the BBC will soon be removing it from Mux B in the rest of the country. Did you do a factory reset or first time installation, not just an automatic scan? Sometimes receivers remember information from previous scans which conflict with the new information. For instructions on how to do this for your TV, see TV Re-tune ____The digital text data will not be present on the HD multiplex, which replaces Multiplex B at phase 2. So it should sort itself out then. Otherwise, it's possible that there is some incompatibility with the current digital text data and your TV. Check that the TV has the latest firmware available at Philips - Contact and Support . Generally they should automatically update when a new version of firmware is broadcast, but this usually requires that the set is left on in standby overnight, so viewers who unplug their sets overnight don't get the updates. (RG47SH)
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AndyG: Yes, you can connect more than one TV to the RF output of the Sky box using a splitter, and tune the TVs into that. The amplifier should be adjusted to just offset the losses of the splitter and the cabling.
I wouldn't recommend anyone buys a second-hand TV without SCART sockets, though. There aren't many Freeview boxes out there that can modulate their output onto the aerial cable going to the TV. Those that did exist have mostly been discontinued.
Of course, if you can find one, you could use that rather than the Sky box. Might be worth getting a stock in to sell with the TV - the Emley Moor transmitter switches over in September and the Belmont transmitter in August. You can also get standalone RF modulators that convert signals from a SCART socket - rf modulator scart switch connectors phono plug lead adapter (RG47SH)
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Haggis: I suspect the signal is now too strong, causing an overload in a booster or in the receiver itself. This causes signals to be smeared into one another.
The quoted allowed signal range of the Humax PVR-9200T is 35-95 dBuV*. On that basis, 60% would be 71 dBuV. Separately, I've calculated that the highest expected signal level before switchover started would have been about 80 dBuV. So we're in that sort of ballpark - in built-up areas you often expect to lose 10 dB of signal because the aerials don't see over neighbouring buildings.
The Confederation of Aerial Installers recommends a level for digital signals of around 45-60 dBuV. For analogue signals it is 60-80 dBuV. The predicted level for BBC Two was 98 dBuV - way over the recommended limit.
The new BBC A multiplex is running at 180 kW and on BBC Two's old frequency, for a predicted 90.6 dBuV. It's very likely that the high-power signal is so distorted that the receiver just isn't able to decode it, and has chosen a weaker signal from somewhere else entirely.
If you have any boosters or amplifiers, you should remove them. If that doesn't help, or there aren't any, I recommend adding an attenuator to reduce signal levels, possibly by up to as much as 20 dB.
Why do Humax claim that the box can handle 95 dBuV? My guess is that is what it can handle when inside a shielded test lab with only one multiplex operating and no other signals. In the real world it has to contend with five other multiplexes, up to five analogue signals, signals from more distant transmitters, TETRA radio below the TV band and mobile phones above it.
Do ensure that you're doing a first-time installation. The most recent update made the 9200T do this when you select Automatic Update, but to be absolutely sure, use Default Setting. You will lose all the recording schedules and it will revert to 4:3 output, so make a note of the settings first.
The latest software is PGXTF 1.00.23 - you can check the version by pressing Menu, 5 (for System), 1 (for Status). The Loader Version should be 'a 4.09'. If the loader version is older than this it may not be able to auto-update when new software is broadcast.
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Angela: Loft aerials are not recommended for low-power digital as the brickwork and tile reduce the signal level, and hard and metal objects in the loft itself (particularly water tanks) cause reflections.
If it is a Group B aerial, you will struggle to get Multiplex C and D, and the low-power HD multiplex, because they are outside that group. However, don't rush off to change it - all transmissions will be inside Group B after switchover, as are the channels suggested for any new local TV multiplexes that might start up later.
Usually multiplex 2 and A are the first to start going wrong, among the multiplexes that are in-group, if there is a problem with low signal or added interference, because they require more signal than the others at the moment.
If you're getting reasonably clear analogue pictures, you'll probably be fine with the current aerial after switchover. It's only a couple of months away now, so unless you're really desperate for those channels, I'd just wait and see.
If you did have a rooftop aerial fitted, Digital UK's prediction is for completely reliable service. Be wary of installers suggesting tri-boom or X-type aerials, or even Yagi aerials (simple flat rod elements) with more than about 14 elements! You are in a very strong signal area and a high-gain aerial will likely give too much signal after switchover, causing problems rather than solving them.
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Ada: I can't find any manuals for Wharfedale integrated digital TVs. For their set top boxes you do this:
1. Press MENU on the remote to open the Main Menu.
2. Press the down arrow to move the highlight to Installation. Press Select to go to the Installation menu.
3. Press down arrow to highlight First Time Installation. Press Select.
4. It prompts 'Are you sure you want to delete all channels and settings for first time installation?'. Press the left arrow to move the highlight to Yes, then press Select.
5. It should then ask if you want to start an automatic search. Make sure Yes is highlighted, and press Select.
If that doesn't match what you're seeing, can you post the TV's model number and we can see if there's a manual available online somewhere.
Basically you're looking for an option called 'First Time Installation', 'Factory Reset' or 'Default Setting'.
It looks like Wharfedale have licensed their brand name to Argos for digital TVs and set-top boxes, and Argos have rebranded other manufacturers' equipment, so it's a bit harder to find the documentation and any necessary updates than for some less-well-known companies that specialize in digital TV equipment.
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Allyson - see Freeview reception has changed? | ukfree.tv - independent free digital TV advice . (RG47SH)
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Stan: I'm afraid Sky require you to keep subscribing to keep time-shift and recording features. You can't even play back programmes you've previously recorded. You can cut back your service to just a basic entertainment package, though.
You should still be able to watch all free-to-air HD channels. Sky say BBC One HD, BBC HD, ITV1 HD, 4hd, Channel 5 HD and Luxury Life HD - see FREESAT from Sky - What can I watch? for a full line-up of what should still work if you cancel your subscription (this is what you get if you buy just a viewing card without subscribing).
As Brian says, if you want recording and time-shifting without subscribing to Sky, you can replace the Sky box with a Freesat+ HD box. Channel 5 HD is not available through Freesat yet, and 4hd is due to launch shortly. You might find you get a different regional variant of ITV1 and ITV1 HD depending on your location, because some variants are only available encrypted.
For a list of channels available on Freesat, see Free Digital TV Channels - freesat . Some channels listed on Sky's free service are free-to-view: encrypted, so only watchable with Sky's hardware and viewing card. (RG47SH)
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Friday 1 April 2011 5:17PM
Sarah: You may be using the Waltham transmitter. Multiplex A, which carries QVC, was moved to a different frequency on Wednesday, to avoid problems when The Wrekin, Lark Stoke and Bromsgrove switch over next Wednesday.
You will need to retune to get this channel back. You should do a 'first time installation' to ensure that the box has no memory of where the channel used to be - see TV Re-tune for instructions on how to retune your box. Some boxes won't store the new information if they already think they have the channel stored.
If this is the case, you will need to retune again on the 13th to keep ITV1, ITV1 +1, ITV2, Channel 4, Channel 4 +1, More 4, E4 and Channel 5.
You could alternatively be using the Sandy Heath transmitter, in which case you would have had to retune on Wednesday to keep the BBC channels. If you did this before 6am, some services may still have been off. Again, another retune will probably sort it out. (RG47SH)