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www.southgatearc.org
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The picture shows
Robert (G4BWB) my brother in law, on the left and on the right is
the operations manager, Yong Wui Oin, who showed us around and also
Cindy Yeo, the very efficient secretary, whom I suspect really runs
the place!
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Mr. Yong then showed us first around the stores and workshop
areas, all nice and cool and air-conditioned. It was quite a contrast
when we went out into the transmitter hall.
Here it was very hot, even though our visit coincided with the 90 minute
period when the station is shut down for maintenance. To me, apart from
the heat, it was a moment of great nostalgia! Way back in 1963 I was transferred
from Daventry to Woofferton, the station located near the Welsh border,
which at that time was primarily a Voice of America relay station and
was just in the process of having its 50 kW RCA transmitters replaced
by then brand new 250 kW Marconi BD272 units.
Nearly 40 years later, it was a bit of a shock to step into the sender hall at Kranji to see almost a replica of Woofferton, with those Marconi units still giving sterling service. The BBC has always called its short wave transmitters 'senders' for long forgotten reasons and at Kranji they are numbered Senders 102, 103 etc..
The BD272 units need manual wave changing, which in practice means they
need to be closed down for 15 minutes at a minimum to manually remove
some very large, heavy (and hot!) coils, insert ones for a different band
and then tune up the sender on its new frequency. The final anode coils
for the 41 & 49 metre band are very impressive, the
antenna coupling coil is a single turn over a metre in diameter and made
of tubing about 12 cms. across - quite a beast! Doing a rapid wavechange
at Woofferton in cool England made you sweat profusely, I can imagine
in the heat of Kranji, you rapidly lose some weight!
Power for the station is supplied by the local electricity authority
and is transformed down to 11,000 volts to supply the anodes of the two
BY1144 triode valves in grounded-grid configuration in the final stage
of each sender. At full power these draw 26 amps. anode
current, so some quite serious power is being consumed. The senders use
high level modulation, which means they need something in excess of 125
kW of audio to give 100% modulation. This is provided by two more BY1144
valves in class B configuration.
This means that the current they draw varies wildly with the modulation,
thus the current being drawn by the station is not constant, particularly
if all the senders are carrying the same programme. I remember that in
the town near to Woofferton, all the lights in the houses flickered in
time with the modulation and when the Greenwich Time Signal 'pips' were
broadcast at the top of the hour, you could check your watch by your house
lights!
The sender hall is raised above ground level and when we went out of the hall we found ourselves on a balcony overlooking the antenna farm. I soon realised the reason for not going down into the field, the lush tropical vegetation is infested with some very nasty snakes - not a problem I had at Woofferton! Mr. Yong told me that crocodiles had also been spotted in the area. Thus their 4 antenna rigging staff had to take great precautions when going out to their tasks in the field. All the antenna switching is done by air operated switches remotely controlled from the building, which must be a great relief to the staff!
Although the station is now operated by Merlin, the station still has a BBC 'feel' to it and I was interested to learn that the station operates on a three shift system with similar hours to that worked at the UK stations. Day shift is I think 09.00 to 17.00, evening shift is a short one until 23.00 and the night shift is the long one until 09.00. This used to be quite a good system, well liked by most staff, as it meant on evening shift you had most of the day free and could still be in bed by midnight.
Programme feed to the station is by satellite, via AsiaSat, and I was
interested to hear that they now have no HF receivers for back-up if the
satellite feed fails. BBC World Service in English is available for local
listeners on 88.9 MHz FM, the programme feed for this is
received at Kranji but is fed on to a site located with all the other
domestic transmitters in the centre of the island.
I asked if they receive many reception reports at Kranji from SWLs and was told that they are forwarded to Bush House, London (You know what happens to those!). I mentioned that while I was working on Ascension Island I used to answer reception reports personally, but I am not sure if this will have any effect at Kranji !
Interesting smells coming from the kitchen announced that it was nearing lunch time for the staff, so we bade our farewells to our hosts and suggested we phone for a taxi. Mr. Yong said that taxi drivers would never find the place, so he very kindly drove us to Kranji MRT station. A fascinating visit, full of nostalgia for me, with grateful thanks to the very friendly staff who took time out to show us around.
Having now seen the Hong Kong and Kranji relays, I must now persuade my wife that we need to visit Thailand next!
Richard Buckby (G3VGW)
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