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Mendip, Bristol and relay transmitters - retune require on 27th March 2013
To allow for the launch later this year of 4G mobile broadband, changes are being made to some digital TV transmitters. Many viewers in the South West of England will have to retune after 6am on on 27th March 2013 to continue to receive certain Freeview TV and radio channels.
Having had a good look at my Mendipaerial and googled around on the net I think that my problem may be the aerial itself. It has 8 shallow Xs on the main part and six horizontal bars on the angled reflector at the back, three on the top bit and three on the bottom. My guess is that as it was installed pre-digital and I'm assuming it is a C/D group aerial then at the freqency for channel 49 its response is dropping off (signal strength is 49 and quaility is 10%)compared with that when the BBC was on 61 before March 27th. It still seems to be good enough for ITV which is on channel 54 even though the signal strength for that is 54.
I would welcome comments from the resident experts regarding a better aerial. I will also contact the gentlemen who set up the aerials originally as he's very good and has a lot of local knowledge.
Richard Tonkin: If you are thinking on changing your aerial then you do not really have many options except to go for a group E aerial which spans from 35 - 68, Mendips span being 48 - 58 therefore the group E aerial allowing a good safety margin at either end of the band.
However, as you appear to be located in an area of reasonably good line of sight (in the RF sense) to the transmitter then I would just fit something like a Log 40 as that should be perfectly adequate for your requirements.
I agree with jb38, on site diagnosis is always best - just not always possible.
Those thinking there is any difference between a group C/D aerial for analogue TV signals and for digital TV signals has been misinformed, the signals are all UHF RF and the only difference is the modulation format and that doesn't alter the design requirements for the aerial. The key criteria are primarily about frequency range, gain and directivity as well as ability to reject any 'back/side lobe' reception. It is a sad fact that some of the 'less expensive' aerials have poor performance towards the extremities of the designed reception band, so some group C/D aerials may not perform as well in the Ch48/9 part as they do in the Ch61 part. Hence it may be worth having the aerial changed to a Group E so ensuring you get good coverage for the reasonable future - unless the 'powers that be' decide to make even more changes as has been rumoured.
Further information at http://www.bbc.co.uk/rece….pdf It also gives the colour codes for the different groups, E=brown, C/D=green (it gives all the others as well).
The aerial described by Richard Tonkin is a typical X-fire pattern commonly used for the modified Yagi pattern aerial needed.
i am a retired aerial installer, so i still have my customers, can you tell me when the mendip transmiter wil be completed with updates only my customers who cannot retune themselves . which means a fair milage to retune for them ive been twice now 40miles away to retune so can you give me any idea of completion
colin needs: Changes to the Mendiptransmitter with regard to the frequencies of the existing muxes are complete for the near future. It is possible that two additional temporary muxes could come on air , possibly later this year. This would not affect the existing services. The next possible change might be about 2018 when more frequencies could be under threat of being given over to 4G/5G! This would entail frequency changes for some or all services at Mendip.