Marconi International Marine Company of Chelmsford, Essex.
Various bits of kit used on the ships on which I was a Radio Officer.
The famous Oceanspan VII.
Designed during the Second World War and with a few refinements after, the Oceanspan was all valve transmitter with three 807s as the final output stage giving 75 watts or (optimistically) 100 watts.
The BLUE dials on the right were all the MF settings and the RED dials were for HF. It was all crystal controlled and therefore relatively fixed frequencies.
The MF frequencies (CW Only) were normally:
410kc/s, 425kc/s, 454kc/s, 468kc/s, 500kc/s and 512kc/s and were selected by the lowest blue switch.
The Black switch on the right hand side was to select the ‘metering point’.
The RED side was for HF and could select the BAND,
Another of the RED switches chose the crystal for the selected band. The dials above are for aerial tuning.
The aerial connection was via the ceramic spout on the top of the transmitter. This would normally be a copper (quarter inch pipe if I remember correctly) uninsulated connection to the Aerial Switching unit.
The aerials were typically a main aerial which was often a high ‘T’ aerial slung between the two masts of the ship. The reserve or emergency aerial was connected to just about anything, slung between just about anything and was often not that good.
On AC powered ships there was a big transformer in the base unit but on DC powered ships this was replaced by a large electric motor taking DC in and supplying AC out. This had to be started before the transmitter was needed and made a horrendous noise (audibly).
The Marconi Atalanta receiver:
Receive range: 15kc/s to 28Mc/s in ten switched bands. 16kc/s was used for the Rugby (MSF) time signals.
IIRC 31 valves (not necessarily 31 valve envelopes as there may well have been some double triodes etc.) The user manual for the Atalanta Receivercan be found HERE
‘Lifeguard’ Auto Alarm
It was tuned to one frequency -
As you can imagine, with static in the tropics these things were always going off in error.
Another function that the Auto Alarm had was that of being a watch-
The "Lifeguard" was designed and installed in about 1965. The operator could either hear the signals via a built-
It was populated with valves: 2 x EF85, 1 x E83F, 5 x D77, 1 x B309, 9 x E90CC, 1 x 9U8, 3 x E180CC, 1 x 6AU6, 1 x LN309.
There were alarm bells on the bridge and in the cabin of the operator. It was powered the emergency 24V DC from the batteries or from the ship’s mains.
The Radio Room Clock
The radio room clock is marked with the times of the statutory ‘Silence Periods’ shown in Red & Green.
The Red Silence Periods were for the 500kHz watch and it was a requirement of All Radio Officers that they maintain a silent watch on 500kHz for the three minutes (15-
As previously stated above, when a Radio Officer was not on watch the Auto Alarm took over that watch.
We were not required to monitor the Green Silence Periods as these were for the 2182kHz emergency frequency in the voice band. To be honest there was virtually no traffic on that band except when near the coast when there was ship-
The AKD -
The Automatic Keying Device was an electro-
Inside the AKD there were three Paxolin wheels of about 3” diameter on a motorised shaft. The shaft turned the three wheels once in one minute.
The wheels had detents in their circumference and micro-
The first wheel had detents in the pattern of:
S O S S O S S O S de (Ship’s Callsign e.g. GBZT twice)
The second wheel had 12, 4 second dashes with one second spaces for the Auto Alarms to trigger.
The third wheel had two 29 second dashes for DF (direction-
The switch on the left under the lights selected where the transmitted signal would would be sent. The options were:
The Main Transmitter
The Emergency Transmitter
AUX (not normally used)
AA to send the signal to the Auto Alarm to test both the AKD & the Auto Alarm itself.
The switch on the right gave a choice of:
Sending the Morse code by hand
Sending just the Alarm signal
The full distress signal
To operate the AKD the ‘Start’ switch was pressed down, the motor started up and the unit whirred into action. The message from the first wheel was transmitted, the unit swapped to the second wheel and then to the third. Once the cycle was complete it went back to the first wheel and repeated the sequence until it…
Was Stopped by an operator, it ran out of power, the ship sank…
Under test (or operation of you were so unfortunate) the machine made a whirring (the motor) a clicking (the micro-
A typical radio room of the time.
I must state that this is not one of mine and it is not me in the photo but it was very typical of the radio room on any Marconi radio room.
As Marconi employees we were sub-
Looking at this typical Marconi radio room:
From the left at bench level -
Then there is the Auto Alarm and (behind his head) the Automatic Keying Device, then the Oceanspan main transmitter.
Above the ship’s call-
The Emergency Lifeboat Transmitter
All ships needed to have a transmitter which could be deployed to a lifeboat. To the left is a photo of the type that I travelled with on all but my newer ships. This thing is about the size of a small dustbin, about 16” diameter and 3’ tall. It had two handles on the top to allow it to be manhandled, the top was sealed with a waterproof dome (shown on the right on the photo) and powered by the pedals.
It transmitted on 500kHz and 8364kHz (though I am not aware that anyone monitored that frequency, it was just in the middle of the 8MHz band and might have been heard by a coast station). It had a Morse key and some aerial matching knobs. It was all valve technology.
Well, after you had recovered from the hernia of getting it into the lifeboat and survived the drop into the oggin your problems started. There was a wire aerial which had to be tied on to an oar and had to be held aloft by one poor soul. The radio operator had to clamp the barrel of the thing between his knees and be stable enough to send Morse code.Two other poor souls had to pedal the damned thing! Being valves, it had to be pedalled for at least 40 seconds for the valves to warm up, then the poor operator could start sending his distress signal. If the pedallers slowed down or stopped the whole process had to be started again. I only tried it once, during a lifeboat practice somewhere up a massive river in the Borneo jungle. God help anyone who really needed to use it!
Thankfully, some time in the very late 1960s this cumbersome thing was replaced by a transistorised version which could easily be strapped to the operators knees and hand-
Direction Finding (DF)
Direction Finding equipment consists of two parts. The specialised antenna system and the instrument on the bridge of a ship that makes use of the signals that the antenna gathers. Below left we have a typical ‘cross-
The Wikipedia entry for Bellini-
Basically, looking at the right hand picture above -
This null will occur at relative bearings of 0 degrees and 180 degrees. A separate receive aerial, called the ‘Sense’ aerial’s signal is added to the equation to work out which is the bearing of the DF Beacon.