Aerial Lingus

Ian Jackson, who contributed these pictures, writes:

Here's a couple of photos of the UHF receiving aerials at Keeper Hill, about 10 miles east of Limerick.
There are two sets of aerials here, mounted on telegraph poles. Both are pulling in the UHF signals from Northern Ireland. One set is for Divis, and the other is for Brougher Mountain (both very long hauls). I believe that the signals were originally supertrunked into Limerick for the CATV system, but later they were also re-transmitted by MMDS from Keeper Hill itself (which probably also replaced the supertrunk cable feed).

Signal quality was generally pretty good, but they did suffer from occasional bouts of very sharp selective fading. I vividly remember watching Startrek one evening in my room in Limerick Jury's Hotel, when suddenly the sound went horrible, and disappeared. After about 20 seconds, it came back, only for the colour to disappear. After about a minute, the whole picture went off and, after a few more seconds, returned. All was well for a few minutes, when the whole thing happened again, but in reverse order. I guessed what was happening, but next day the cable TV guys confirmed that this did happen. Under certain conditions, a very narrow, deep notch wanders up and down the UHF spectrum, talking out each TV channel in turn.

The UHF aerials were taken out of service when they got the 6GHz link running, which gave them a feed from Sieve Bawn to the various MMDS sites (for re-transmission on 2.4GHz, and for the cable systems).

Similar long-distance reception was used for the Cork CATV system. This time, the receiving site was in a brick hut, on the top of Seefin 'Mountain' (just north of Dungarvin). The transmitter was Presely.
There there was a single high-gain aerial (maybe Fuba) INSIDE the hut, pointing out through a fibreglass 'window'. Various bits of tinfoil were dangled to discourage co-channel reception from other directions.

The four Welsh UHF signals were converted to Band 3, and sent via coax down into Dungarvin. At the back of someone's garage, they were converted to Band 1, and supertrunked maybe 50 miles to Cork (the way the road went). There they were demodulated to baseband video and audio, and re-modulated with suppressed syncs before being added to the rest of the CATV signals. Later, they also went out on the Cork MMDS system. The Seefin - Cork link was also superseded by the 6GHz microwave system.

All great fun!

Many thanks for that, Ian.

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