Metal in the Sky

Introduction

In the days of VHF 405-line TV, reception in Oxford was at first only available from Crystal Palace (well, at very first from Alexandra Palace) and Sutton Coldfield (BBC), plus Croydon and Lichfield (London and Midland ITV respectively). BBC reception on Band I was fairly standard from either direction (mostly 2- and 3-element arrays plus some larger). For ITV, large Band III arrays were common - the (even) choice between Croydon and Lichfield depending on both location and preference. During the 'second phase' Oxford became a primary service area with BBC being transmitted from Beckley and ITV (Midland) from Membury, although many forlorn 'double sixes' and a few 'double nines' survive to this day.

Now it is possible to receive reliable (terrestrial analogue) UHF TV in Oxford from at least four different programming regions.

Easy

There is a local main transmitter at Beckley (2·8 miles from us in Old Marston) which most people in Oxford tune to - it provides BBC South (Oxford), BBC-2, Carlton Central South, Channel 4 and Channel 5 (at lower power). We have a J-Beam Logbeam LBM2 array (19 feet high, in the roof) which gives perfect reception.

Standard

Reception from Hannington (32 miles exactly South from us) is also good - it provides BBC South, BBC-2, Meridian Television, Channel 4 and Channel 5 (at lower power). It is the transmitter of choice in some parts of Oxford where the line of sight to Beckley is obstructed. We have a J-Beam Multibeam MBM46 array (19 feet high, in the roof) with a Labgear CM-series head amplifier which gives almost perfect reception - an outside array would probably not need amplification.

Quite a few dual installations (Beckley : Hannington) can be seen in Oxford. Before Channel 4 started, it was enough to combine the two arrays with a diplexer; now, especially with the advent of Channel 5, channel filters are really needed to avoid ghosting on the Beckley signals.

Fringe

Fringe reception is fun! You never quite know what to expect - the weather has a major influence on the signal - sometimes the picture will only just stay put during the troughs of deep fades and is very noisy, whilst at other times (usually during high pressure) it can become almost noise-free. Even during the worst conditions, however, reception from Sandy Heath and Crystal Palace is watchable, with colour and NICAM stereo (if not always Teletext). The liveliness of fading, snowy images with passing ghosts etc certainly improves the duller programming!

Reception from Sandy Heath (49 miles from us and almost on our line of sight to Beckley), which provides BBC East, BBC-2, Anglia Television, Channel 4 (Channel 5 is very weak), varies depending on the weather. We have a Triax Unix 100 array (17 feet high, in the roof) with a Research Communications ultra-low-noise GaAsFET head amplifier - the array really needs to be put outside.

Reception from Crystal Palace (56 miles from us), which provides BBC London, BBC-2, Carlton / London Weekend Television and Channel 4, also depends on the weather. Channel 5 from Croydon is now at about the same level. The John Radcliffe Hospital, perched on Headington Hill, is directly on our line of sight - we must ask them to move their buildings a few hundred yards to the side, although the hill should be moved too. Consequently, we only have a refracted and/or scattered signal and atmospheric effects are often very lively. We have an Antiference Extragain XG21 array (30 feet high, above the roof) with a Research Communications ultra-low-noise GaAsFET head amplifier. This was once knocked out during a thunderstorm.

Anecdotally, Crystal Palace reception is said to be relatively good in Rose Hill because it lines up with the M40 cutting through the Chiltern Hills. Looking at the map shows that things are never that simple...

A quite small number of Crystal Palace UHF arrays can be seen in Oxford, and most of these are probably disused relics of the first BBC-2 service. We have only spotted a couple of 'definite' Sandy Heath arrays. It seems that very few people are interested - or that, like us, they prefer to put the hardware inside the roof.

Others

Reception from Sutton Coldfield (63 miles from us) is also feasible as a fringe choice; but the programming (BBC West Midlands, Carlton Central West) differs so very little from the local Beckley output that we don't seem to watch it. Channel 5 from Lichfield is at about the same level. At some locations to the South-West of Oxford good reception from Mendip (71 miles from us: BBC West, HTV) is also possible.

During tropospheric 'lifts' the world is your oyster (well, our Crystal Palace UHF system gives an East-South-East window into Europe anyway). From Oxford, try Rowridge, Ridge Hill, Lark Stoke, Mendip... for an idea of conditions. Then, of course, there is VHF Sporadic E - another story, another page...

It is unfortunate that terrestrial digital decoders are currently like hens' teeth, or we should have some idea whether the experimental Crystal Palace service ever reaches Oxford. By the time we can get one, digital will have 'gone national' anyway [update 25 November 1998: we have, and it has]. Finally, we await the new Restricted Service Licence stations with interest [update 6 June 1999: The Oxford Channel has just opened on Ch. 47].

Techie stuff

Combining the signals from high-gain systems requires some care if one is to avoid unwanted ghost images from the off-beam arrays. One also needs to take care not to overload high-gain amplifiers with (very) strong signals from the local transmitter. However, it can be done using channel filters, diplexers etc and the results are well worth the trouble. There is no appreciable adjacent-channel interference between Carlton/LWT (channel 23) and Anglia (channel 24).

Although it might be tempting to use a single wideband array with a rotator, or perhaps just antenna switches, the hassle-free and instant channel changes given by a permanent dedicated system are greatly appreciated by viewers - especially when more than one TV set is on!

Links

• [Link to transmitter information here]
• [Link to article about antenna system and technical details here]
• [Link to article about digital terrestrial TV here]