All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Chelsea
A small indoor portable aerial will not work inside a caravan! The metal body of the van will prevent any signal reaching the aerial.
You need a 'log periodic' aerial, to cover all possible transmiters where you park up, and ideally with an easily erected mast system. Might be worth looking at Labgear LABLPC 400mm 9dB Compact Log Periodic 20: Amazon.co.uk: Electronics (others are available) but this is a short type and some areas may need a stronger reception (longer arm with more cross elements) to recieve the weaker signals better.
There are types available to mount on the A-frame of your caravan and others that are ground mounted with guy ropes. You will always need to adjust the direction it is pointing so it is aimed at the transmitter serving the area you are staying and you need to check whether the cross arms need to be sert horizontal or vertical (the picture linked to above is set horizontal).
When you know where you ar likely to be staying, check which is the local transmitter and not the polarity (H or V) and the channel numbers for the multiplexes provided. When at your location, erect the aerial, aim it roughly with a compass (there is information on this sire about the exact location of all the UK TV transmitters and you have to work out the compass bearing between that and your location), set the polarity (the aerial instruction book will tell you how, so worth reading it) and thenconnect the TV and retune it - again using the TV instruction manual noting you may need to do do a complete reset from an 'initial installation' setting. The manual should tell you how to do that. (That is necessary to eliminate all previous settings that would be for a different location.)
Hope that helps?
| link to this comment |
david:
I suggest you ask Sky themselves. They may suggest a 'multi-room' package or a second subscription, they can be a bit unpredicatable.
Make sure youn explain clearly what you actually want to achieve and with what equipment as they sometime tell you to distribute the RF signals from an adapter on the box - but that means all TVs get a poorer quality picture (except the one connected by HDMI/Scart) and all will have to view the one programme on all TVs! Separate boxes has an advantage but each needs feeder cables from the LNB (2 per box for Sky+ or one for non-Sky+ boxes).
| link to this comment |
Bren
4G problems are few and far between and generally only affects transmission of channels 58 and above (and very rarely on lower channels).
When a new 4G transmitter is switched on a few people may have interference problems and they should contact @800 for assistance and advice.
It is not wise to start assuming things too soon without clear and precise checks being made first.
It is highly unlikely that Anita's problems are at all related to 4G, more likely water in the cable as MikeB suggests.
| link to this comment |
Kieran
Why did you have to move the aerial from the outside of the roof to the inside (loft)?
Outside aerials generally receive better signal strength than those in the loft because of the bricks, mortar, tiles, etc being 'in the way' of the signals. Did you have it properly aligned to point at the Crystal Palace transmitter? I ask because a friend live just off Russel Road and have excellent reception on a log periodic on the roof wiothout any need for an amplifier.
I would suggest having the alignment checked or perhaps replacing the current aerial with a log-periodic (to suit future channel allocations) mounted outside for preference. Be careful about amplifiers as too much signal strength often gives worse results as it's 'too much of a good thing' as quality is more important than strength. Similarly, too little can cause problems too! For most TV sets a strength displayed as between 50 and 80 % is adequate, more than that is usually too much! Less than that is often too little.
| link to this comment |
Anthony
High gain wide band aerials do not have a 'flat' frequency response (usually poorer at the lower channels end), that's why the current advice is to use a log-periodic as they have a much more even response across the whole band that is currently in use and will be so for the foreseeable future. So your suggestion is not ideal for this situation.
I always used a log-periodic on a pole with guys and had decent reception at all the camp sites I visited in England, Wales and Scotland, even in realtively poor recption areas. It was crucual to align the aerial correctly of course. I used a battery (of the car type) powered 14" TV set and never had problems. Others did not have log-periodics and had reception problems that even I as an experienced TV service engineer could not resolve - the aerials were just not up to the job.
I note you are suggesting 32 or 48 element aerials. These have a much narrower reception angle pattern and are far more difficult to allign correctly - and may not be at all suited to the more difficult local terrain conditions. Further, you should m=not be aiming to get 'maximum' signal strength but adequate, too much will mean no reception of some services as the tuner gets 'swamped' and what signal is received cannot be decoded so giving the 'No Signal' warning. Likewise too little will result in apparent loss of some programmes on the weaker multiplexes. You need the TV rto display a strength between 50% and 80%, less or more is not good!
| link to this comment |
Antony
You are talking of a fixed installation at your location, the answer was aimed at a question from Chelsea concerning a moveable system suitable for use with a mobile caravan/tent. The two are quite different requirements, especially as different channels are used across the country so an aerial capable of equally good reception everywhere is required - only a log-periodic can provide that and any form of Yagi cannot by its very design. A 'wide band' does not give even reception across all channels, which is a primary requirement of any 'mobile' system.
One other problem with a mobile system is that at some locations it can be very near a transmitter, so a 32 or 48 element may well be too high gain and result in the ubiquitous 'No Signal' message due to excessive gain. Or it may be quite distant from a transmitter in which case the alignment with a high gain aerial becomes far more critical. The acceptance angle of a 48 element can be as little as 3 degrees which is very hard for an amateur to set up accurately - especially if it is raining or blowing a gale at the camp/caravan site.
| link to this comment |
I used to live in Cropwell Bishop, not far from East Bridgeford, and as far as I know the village should be well served by Waltham apart from a few cottages by the River Trent. Gunthorpe and Lowdham are all served by Waltham and it is not far away with no significant hills to cause problems. So I don't understand why apparently so many are on a Yorkshire/Humberside transmitter and not a Notthingshire/East Midlands transmitter that is much closer!
I used to service TV set in that area in the analogue days and everyone I visited was on Waltham, as expected.
If the aerial points in the general direction of Bingham, then you are on Waltham. If it points towards Newark, then you are on Belmont and will be unlikely to get the Notts service.
| link to this comment |
dixon:
You don't tell us anything about what equipment set up you have nor loacation.
Do you have a TV in another room and is it using the same dish/LNB? Does it have the same problems? How are the cables fed from the dish to your TVs?
With that sort of information we may be able to give some advice.
| link to this comment |
Bren
Twisting cores and sheilding together is *not* the correct way to connect three pieces of coaxial cable together - the impedance mismatch causes horrendous problems. You say the tuning was rather tricky - I'm not surprised as the tuners will have been compromised by the grossly incorrect cable joins.
Pointing two aerials at the same transmitter does *not* double the signal strength, it could in fact ruin reception of several channels! Aerials and the cabling of them do not work the way you seem to think. As you found out eventually!
I strongly suggest you borrow a decent book from the Library about how RF system work with particular attention to impedance matching, standing waves and lead lengths.
| link to this comment |
Wednesday 28 May 2014 12:29PM
Bren
The output power (ERP) of a transmitter largely determines the transmission distance, but obstructions between the transmitter and receiving aerial can seriously affect recption. Tall building, hills and mountains all have an effect.
Waltham has different ERP for the PSB muxes from those of the COM muxes, a common variation found at many full service transmitters. Lower power reduces the signal strength, I suspect you are equating 'strength' with 'robustness', which is not correct.
That you now have satisfactory reception from Waltham suggests you have elminated whatever was causing the problem.
A word of warning if you consider bringing the Nottingham transmitter back into your system, you can ruin your reception of all channels if you don't do the connection correctly. I would strongly recommend use of a UHF switch with two inputs and one output such as this at
Two Way F Plug Aerial Switch | Maplin (others are available), do *not* use a simple splitter/combiner as that will make signal reception much poorer! The F-type connectors are poften preferred nowadays and can be fitted to most good quality coaxial cable as used for UHF TV aerials or satellite LNB feeds.