Gerry Keane R/O in tranmitter room.
1902 : Technical Information
By todays standards, the 1902 equipment was very straightforward. The transmitter consisted of a huge battery of 98 Siemen's M type dry cells arranged in series - parallel i.e. 7 parallel rows of 14 cells, each in series giving 14 to 16 volts when charging a 12 volt accumulator/battery. There were no voltmeters or ammeters on station so staff had to rely on listening to the accumulator ''gassing'' to know when it was fully charged. The accumulator battery supplied 6 to 8 Amps to a 10 inch induction coil, the secondary of which was connected directly to a small spark discharger mounted on the coil base. One knob of the discharger was earthed and the other connected to the aerial. No capacity was used, the aerial earth capacitance being sufficient in itself. The key for the transmitter was a large brass instrument using quarter inch diameter platinum contacts worth some 30 shillings at that time.
The spark length was adjustable between 2mm and 1.2cm depending on the working distance required. Using over 1.2cm and the wave train was damped due to extra spark gap resistance and consequently efficiency reduced. The system was known as Plain aerial.
On the receiving side, the equipment was quite simple but required skill and patience to get it to function at its best. The signals could be read by three methods:-
1. From the sound of the coherer.
2. From the call bell.
3. From the ink marks of dots and dashes made by the morse printer.
The antenna system comprised of a 120 foot mast with a twin vertical wire aerial supported from the top and using bamboo spreaders 6 feet long to keep the wires apart. Both wires were connected together top and bottom and used what was then called a ''cowtail'' lead-in insulator to take the aerial into the radio equipment.
The station at this time was equipped with a 5 kilowatt and 1.5 kilowatt transmitter and it is interesting to note the lists of ship stations worked during the mid 1920's when records were made of the range of GMH during day and night hours. On the 24th July 1924 at 1041GMT, the Helligolav was worked at 600 miles west of Malin Head, whilst the Regina 490 miles west was in contact at 1015GMT on the 22nd August 1924. The average distance during daylight hours appeared to be 450 miles. At night this extended to 1200 miles west whilst working the Samuel L Fuller at 0003GMT on the 19th July 1924. Then on the 26th September 1924 on a night duty at 0612GMT, the Marinula established contact from 1300 miles west of GMH. The Columbia was reached at 1400 miles west again on a night duty at 0559GMT on the 23rd January 1924. Malin Head Radio was certainly getting out well and the location of the station being close to the sea on two sides and built on marshy low lying ground was well chosen.
1988- 1999
Until 1988, the station operated on 500kHz and 2182kHz. However, on the 31st of December 1988, the last transmission on 500kHz, running 1000 watts, was made and Malin Head went off the air on this morse code frequency. Today the station continues on 2182kHz and controls 4 VHF remote stations at Malin Head, Glen Head, Belmullet and Clifden. These are operated via landline to the various remote sites. The VHF equipment is manufactured by Motorola, running approximately 45 watts output to colinear Antennas.
| On 2182kHz and the working frequencies, the output power from our transmitters is 1000 watts on the 1677kHz (our primary working frequency) and 1644kHz and 250 watts carrier peaking to 500 watts (on speech peaks) on 2182khz, amplitude modulated SSB is used on the working frequencies. Our transmitters which are co-sited within the radio station transmitter room are fed underground by very heavy duty co-axial cable to the antenna tuning huts at the base of 150 foot masts. There are two 150 foot masts on site. The antenna tuning brings the antennas to resonance on the various frequencies. Buried under the station grounds is a large network of earthing wires and radials in order to achieve as near perfect efficiency as possible. Strung between the two 150 foot masts is the old 500 kHz wire T-antenna which we now use as a reserve receiving antenna should our remote receive antenna need repairs. The various receivers on station, mainly Hagenuk and Dansk, are fed via co-axial cable out to the station boundary fence and under neighboring farmer's field to a termination unit to convert 50 Ohm co-ax to the 600 Ohm open wire feeder which runs approximately a half a mile to the large T-wire antenna strung between the 60 foot poles at the summit of a nearby hill. | Gerry Keane R/O in tranmitter room. |
On 2182kHz and the working frequencies, the output power from our transmitters is 1000 watts on the 1677kHz (our primary working frequency) and 1644kHz and 250 watts carrier peaking to 500 watts (on speech peaks) on 2182khz, amplitude modulated SSB is used on the working frequencies. Our transmitters which are co-sited within the radio station transmitter room are fed underground by very heavy duty co-axial cable to the antenna tuning huts at the base of 150 foot masts. There are two 150 foot masts on site. The antenna tuning brings the antennas to resonance on the various frequencies. Buried under the station grounds is a large network of earthing wires and radials in order to achieve as near perfect efficiency as possible. Strung between the two 150 foot masts is the old 500 kHz wire T-antenna which we now use as a reserve receiving antenna should our remote receive antenna need repairs. The various receivers on station, mainly Hagenuk and Dansk, are fed via co-axial cable out to the station boundary fence and under neighboring farmer's field to a termination unit to convert 50 Ohm co-ax to the 600 Ohm open wire feeder which runs approximately a half a mile to the large T-wire antenna strung between the 60 foot poles at the summit of a nearby hill.
Regarding our SSB transmitters, they were recently replaced by one manufactured in England by SPT electronics at Southend-on-Sea. We have a standby power plant to generate our own electricity in the event of mains power being off at any time. Power output available from the generator is 60 KVA.
Mike Mullins R/O Malin Head Coast Guard Radio On Watch > |