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Old 12th Jun 2018, 1:54 pm   #1
Richard_FM
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Default Irish Analogue VHF TV Transmitters

I've been looking for a definitive list of Irish TV VHF transmitters.

I have a World Radio book with details from just before the analogue switch off, but by then a lot of UHF transmitters had replaced the VHF ones.

I was mostly interested in the era when they had a dual 405 / 625 service, & during the early days of RTE2, when most of the 405 line frequencies were recycled for this channel.

Ireland was one of the few places that managed to get 2 nationwide channels on VHF with 625 lines, so I'm interested to see how they managed with 11 channels, especially with a lot of transmissions crossing the border & Irish sea.
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Old 12th Jun 2018, 7:56 pm   #2
Focus Diode
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Default Re: Irish Analogue VHF Transmitters

I have a list of transmitters from around 1982. They were still three 405-line relay transmitters in operation with a note to say they would cease when replacement 625-line services became available.
Sure I still have it. I'll have a look for it and upload it.
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Old 12th Jun 2018, 11:05 pm   #3
standing wave
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Default Re: Irish Analogue VHF Transmitters

Scan from 1966 RTE handbook listing 405 & 625 networks.
Terry
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Old 13th Jun 2018, 1:32 am   #4
kan_turk
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Default Re: Irish Analogue VHF Transmitters

Quote:
Originally Posted by Richard_FM View Post
Ireland was one of the few places that managed to get 2 nationwide channels on VHF with 625 lines, so I'm interested to see how they managed with 11 channels, especially with a lot of transmissions crossing the border & Irish sea.
Nationwide coverage for two channels was not quite achieved using VHF only - an additional channel 'J' was added at the hf end of band III and two high power and one medium power UHF transmitters were employed to complete the coverage

J
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Old 13th Jun 2018, 2:13 am   #5
Synchrodyne
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Default Re: Irish Analogue VHF Transmitters

The attached items might also assist:

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The 1963 list shows that the main transmitters were all 100 kW erp, regardless of whether they were Band I or Band III, whereas the conventional wisdom was that to equalize signal strengths at the edge of a service area, around 300 kW erp was required at Band III against 100 kW erp at Band I (with higher powers than those of little value in extending the service area.)

Two-channel nationwide 625/50 coverage using only VHF channels was perhaps not so unusual. Here in NZ it was done using 9 VHF channels (3 Band I and 6 Band III.) When Band III was extended upwards to accommodate first one and then another extra channel, a third VHF network was shoehorned in, although I think with lesser coverage. To be fair, in NZ for a given high population coverage, the required geographic coverage was somewhat less, a situation that might not have obtained in many Northern hemisphere territories.

Cheers,
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Old 13th Jun 2018, 3:24 pm   #6
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Default Re: Irish Analogue VHF TV Transmitters

I am pretty sure the aerial transmitter polar patterns at the Mt. Leinster transmitters (VHF band III, Channels IF and IJ) were altered a few years before analogue shut-down - both because my reception of them dropped markedly and also I think I had read the changes were to avoid interference to UK DAB transmissions.
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Old 13th Jun 2018, 10:23 pm   #7
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Default Re: Irish Analogue VHF TV Transmitters

Here's the transmitter list from January 1982.
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Old 13th Jun 2018, 10:43 pm   #8
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Default Re: Irish Analogue VHF TV Transmitters

Thanks for the feedback everyone.

Ireland has had an interesting history of TV distribution, especially the analogue cable systems, "pirate" relays & wireless cable.
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Old 15th Jun 2018, 6:23 am   #9
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Default Re: Irish Analogue VHF TV Transmitters

Just noticed Maghera transmitted RTE-1 in BI horizontally polarised yet RTE-2 was in BIII vertically polarised. Most unusual.

I once received RTE-1 channel B via Sporadic E which was surprising considering the comparative short distance.

I remember what an ex work colleague told me that in the late'70s they still relied on 405-line TV. Broughther Mountain didn't open on UHF until 1978. They received three 405-line services, BBC NI, Ulster and RTE-1.

When they went 625 colour they gained BBC-2 but lost RTE-1.
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Old 15th Jun 2018, 9:52 am   #10
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Default Re: Irish Analogue VHF TV Transmitters

My late father-in-law was one of the first generation of RTE TV engineers. My wife has mentioned that as kids their Mum had something of a downer on them celebrating when in winter it snowed (as kids do) - because their Dad would have a hard time getting to- and from Kippure. There were some tales about preparing to repel the IRA (and not having to) - and now I think about it a funny one about getting locked in the loo while up there alone and it requiring considerable ingenuity and a cool head to get back out again
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Old 15th Jun 2018, 2:43 pm   #11
SteveCG
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Default Re: Irish Analogue VHF TV Transmitters

Focus Diode,

You may be interested to know that Antiference sold a special TV aerial for that transmitter - this was years after UK 405 line close down and so UK interest in Band I & III TV aerials ceased. Now we have Band III DAB...
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Old 19th Jun 2018, 1:00 pm   #12
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Default Re: Irish Analogue VHF TV Transmitters

I well remember doing a stint in Dublin around 1964, the channels available were:
BBC 1 CH1 from Northern Ireland, Ulster TV from N.I. Welsh commercial TV CH 10, RTE from Mnt Kippure, RTE from Balls Bridge Dublin ( Just a low power repeater15 W) and RTE from Mnt Kippure on 625 lines. My main Job at the time was involved with a cable system receiving U/K T.V. off air in the Centre of the City. We obtained quite good results from antennas atop a 100ft lattice mast atop of a multi storey housing block.
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Old 22nd Jun 2018, 8:52 pm   #13
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Default Re: Irish Analogue VHF TV Transmitters

When I saw the title of this thread, it immediately reminded me of a project I became involved with back in the late 1980’s.
I was working for a major UK electronics company, in their special projects division, designing CCTV systems for military, scientific and industrial applications.
One of our more simple, and what should have been straight forward projects, was to supply and fit a ruggedized CCTV camera system to several Royal Navy type 42 frigates The camera was to be mounted on a point quite high above the bridge and looking to the front of the ship, and connected via a co-ax cable to a single ruggedized monitor on the bridge. The installation seemed to go well, and on time, but a few days later we received a phone call to say the picture from the camera went off when the ships radar was switched on.
After being passed from pillar to post I finally got to speak to a member of the crew who was able to describe the problem. It seemed when the radar was switched on the camera picture went dark with only noise showing on the monitor screen. I guessed the camera’s auto iris was closing down due to interference from the ship’s radar, and that some extra screening and de-coupling capacitors would be the answer, and a few days later I found myself driving to Portsmouth.
When I arrived I was driven to a remote part of the docks where the frigate was moored and the first thing I noticed was a HUGE rectangular, parabolic radar array mounted on the ship. To my untrained eye it seemed totally out of proportion with the ship and made it look top heavy. Then I noticed what looked to me like band III dipoles mounted at the focal point of the parabolic array. Without thinking I blurted out “that’s over the horizon radar” – the two men escorting me just looked at each other, gave me a filthy look, and said NOTHING.
After I was handed over to ship’s crew and my silent escorts left, I set about installing the modifications to the camera’s auto iris circuit – three of four .001uf capacitors and a copper screen over part of the circuit, then, up to the bridge to talk with their technical officer. I explained I was unable to test modifications, and by-the-way, was this over-the-horizon radar? To my surprise, he replied “Oh yes, but we can’t power it up here, if we did it would cause major interference with Irish television”. Then he proceeded to flick a few switches, the band III array started to rotate, radar images appeared on screens, and apart from a few sparkles, the picture from the camera remained stable. I was then treated to a demonstration of the radar, a tour of the ship and later, taken down to the ship’s bar, to celebrate the working camera system, and all this time I was wondering what effect all this was having on Irish television because the radar was still on. After several celebratory drinks, my dumb escorts re-appeared and I was taken back to the port reception area, and from there, made my way home.
The following day I made some ‘discreet enquiries’ and was eventually rewarded with an anonymous phone call from a man claiming to be one of the design engineers involved with the OTH radar. He did not tell me much, but he did say that several ships systems had to be modified to cope with the radar which was based on a pulsed klystron and that the output was a “very dirty” 220Mhz.
Dave
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