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RTE Radio One - 729 khz from Cork, Ireland

This is one of the few Medium Wave transmitters operating in Ireland. It was established around 1970 to provide an improved RTE signal in Cork City and to allow for a local version of RTE Radio One to be broadcast for a few hours each day. The 10 kilowatt transmitter was located in what was then a remote area called Ballinure which was located alongside Lough Mahon.


Location of RTE transmitter in Mahon, South East of Cork City
Satellite photo showing inner harbour and Lough Mahon to the East

Closer view showing Blackrock (top half) and Mahon (bottom half). You can make out where the South link road passes the RTE site. To the South of the mast is the Douglas Estuary which no doubt helps to improve the radiated signal.
On this close up, you are looking down on top of the 120 metre high mast. You can see it's shadow going towards the top of the picture and crossing the road. Also shown is the small dam which fills at every high tide and ensures that there is always water close to the base of the mast. This dam is now part of an amenity walkway which passes the RTE site.

Photos of the mast

When this mast was first erected, it was in a very quiet area surrounded by fields. Today, the City of Cork has expanded and now the mast is now alongside the major housing development of Jacob's Island and the Mahon Point shopping centre.
Photo shows the rush hour traffic on the South link road driving past the mast and heading for the Lee tunnel.
This photo shows the pond at the base of the mast.

Closer view from the dam which keeps the water at a high level in the pond.
April 2007 - View from the adjacent walkway showing some development work going on.

Mast Height : 120 metres, Power Output : 10 kilowatts, Frequency : 729 khz
At 729 khz, the wavelenght is appox 412 metres. With a 120 metre mast, this would make it approx 0.29 wavelenghts long and it would behave as a slightly long quarter wave ground plane.
From 1979 to 2004, RTE used to transmit their 2FM music channel here as well on 1278 khz. At that wavelenght (235 m), the mast was 0.51 wavelenghts long and would have acted as an end fed half wave vertical.
Note also that there are 3 sets of guide wires. Along each set on the photo above, you can see 'black' objects. These are insulators which split the steel cable up into smaller lenghts. These lenghts are so small, i.e. percentage of a wavelenght, that they have no effect on the transmitted signal. If they were not used, the guide wires would become part of the antenna system and would  interfere with the radiated signal.

© John Desmond 2007. Last Updated May 2007

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