277F-Techs' memories

You can't keep a good? radar down - Reg Carter
The scene is No 1 Radio School RAF Cranwell Lincolnshire and the time is the 1949 period. Those in control of training decide in their infinite wisdom that it would be a good idea if there was a short interchange between those going down the 'airborne' side of radar training and those people on the 'ground' side of things. The idea was to let each side experience the problems of the other systems.

Obviously with the airborne side reduction of weight was all-important along with the reduced ability of the engine driven generators to produce sufficient power to run things. (Most of the airborne engine-driven alternators only produced about 500 watts at a frequency between 1200 and 2,400 Hz depending on the engine speed). So for us 'air blokes' to be confronted with a radar so big you could walk around inside it was stunning. Mind you I think the ground people were horrified at the, for the period, miniaturisation involved in airborne radar.

Now to get to the point. The air group were introduced to CHEL (Chain Home Extra Low) and were suitably impressed with the Transmitter NT 277 along with display unit DU 5, consoles 15 and 16 as regards size at least. Bloody big !!!!. Enter instructor and advises the class not to bother with the Transmitter/Receiver NT 277 as that was OBSOLETE and we would NEVER meet one so just concentrate on the consoles!!

This is in 1949 and so we did just that little thinking that personally I would be staggered to find them in service when I went for an interview at Australia House in the Strand in 1967 regarding an Observer Radio position. I must confess that I thought it was a misprint in the paperwork sent me concerning the equipment to be worked upon.

But I am glad to have used the old girl even if that elevation system? was the bane of many an Obs/Radio's life.

277 and Sondes -Reg Carter
Situation is the morning 'sonde flight. Released on time and it's very calm, no parachute on the package as we are 'out in the sticks' so it is not necessary and we have to make our own gas. Remember the old Caustic soda ferro-silicon game with the 'A' cylinders and two gallons of water!! So we did not waste gas if we could help it.

Balloon reaches 500 mB (20,000ft) and rate of ascent is slowing markedly. Cry from duty observer doing the wind flight whilst I was doing the 'sonde is "buggers burst !". and "the elevation is 90 degrees" !!!!

Give up the sonde flight ready to restart another and wander over to look at the radar sig. Solid sig sliding down the A scan and the elevation definitely looking STRAIGHT UP. Revolve the azimuth and signal is the same amplitude in all directions (ALL DIRECTIONS) so balloon very definitely directly overhead.

Previously, having nothing to do for a few minutes, I had set out to calculate the terminal velocity of an Astor radiosonde when only slowed by a burst balloon acting as a stabiliser. Since the thing weighed in the order of six pounds (3kg) and had a surface area, when falling in the optimum position, of some figure I now forget, I had assumed the worst case and had calculated the terminal velocity as close to 190 m.p.h. say 300 km/h, and there was this thing hurtling down the beam towards us cowering inside our corrugated asbestos sheet roofed building. It slid down the A scan and never once left the beam. What can you do except pray and hope. It did not hit the building but caught in some trees about 300 yds away and hung there. Of course it KEPT on transmitting and so we had to retune the next sonde to shift it away in frequency and hope (Ha-Ha) that the AFC on that dreadful Astor Sonde Receiver would stay on the new signal even when it was much weaker than the signal coming from the trees nearby.

Being a poor batch of Beritex balloons the second one burst early also and we had to repeat it all again for the third attempt.

"Fun with a 'dribbling' 277" !!!! -Reg Carter
When the 277 was installed at Cloncurry (by DCA I Believe) a minor omission occurred with regard to the AUK aerial. The specification for the six or eight great bolts, which secured the yoke to the pedestal, called for certain copper-asbestos washers to be fitted to waterproof the thing against drips and spray etc. In the case at Cloncurry there had merely been 'star washers' fitted. However the many coats of paint applied over the years had maintained the waterproof integrity of the thing.

Eventually for reasons unknown to me the experts at Head Office sent up a new gyro and elevation motor system and as requested I duly installed it. Since the dear old 277 was engineered on the 'near-enough' principle things were an interference fit (or worse) and a slight degree of BFI had to be used to persuade the unit to take the end of the dish and align it with the bolt holes on the platform of the yoke assembly.

This unfortunately was enough to disturb the paint on the yoke-pedestal bolts, which caused problems. Unknown to me and Bruce Aubrey RMO Qld the yoke had filled with water over the years but being built to Admiralty specifications the 'turning motor' was more than enough to turn the whole thing without any problems. About two days after I fitted the new elevation assembly there was a rather interesting blowing of fuses in just about every circuit which was feeding the slip-rings on the pedestal. The water had seeped down through the bolts and shorted out the slip-rings in no uncertain manner. When Bruce managed to obtain a set of slip-rings he came up to lend a hand with the change over.

More fun ensued when we tried to erect the jib on the tower side to let us lift the aerial and yoke assembly out of the way whilst we changed the slip-ring assembly.

It fouled every cross member on the tower as we tried to lift it to the high position and resulted in the use of brute force to spring the vertical pipe out a little to clear the obstructions on its way up and since it had never been used since installation the many coats of paint on it were reluctant to pass through the collars in which it was supposed to slide.

Once in position, we set about lifting the yoke assembly after removing the bolts attaching it to the pedestal. As it came away and lifted, a torrent of water cascaded out of the yoke arms. It must have been full to the brim for some years and you can imagine the foul stench of the scum laden water which emerged and drenched Bruce and I as we struggled to keep it away from the internals of the pedestal.

To say we were not amused is something of a considerable understatement.

Old age wiring on a 277 -Reg Carter
At Cloncurry I had the misfortune to find that the wiring to the silica-gel de-humidifier used to keep the waveguide dry had gone short-circuit. Little did I realise how long it was going to take to rewire the de-humidifier when I started. The wiring was in "lead-sheathed vulcanised india-rubber', which in the years from installation till 1969 had lain undisturbed as it slowly perished from the heat.

Locating the fault was easy as the black soot on the brittle lead sheathing showed up well once the top of the ducting was lifted. However the perished state of the wiring was so bad that every time you moved it to replace the faulty bit it shorted out about 2-300 mm further back so when completed the fault was still there. For reasons best known to those set in authority above both Bruce Aubrey and I there was a reluctance at Head Office to supply a roll of 'three-core' which would have solved the problem in an instant. Instead I suppose I made at least a dozen 'reconnection' using terminal blocks and some equally suspect lead-sheathed wire in the alternator room. Took me three days along with a lot of sweat and blaspheming to fix the problem but I dreaded the thought of a 'heavy footed observer' tramping on the ducting and disturbing the wiring again.

A 277 in the hands of a good operator -Reg Carter
During the late 60's the Yanks were flying X-ray packages (I think) from Charleville. These packages had to be recovered and it was necessary to track the balloon both UP and DOWN so that an aircraft/chopper could retrieve the package. The balloon was a big one and for tracking, two large targets were attached to the package along with the necessary parachute, which of course out in the 'sticks' we normally did not bother to use.

One afternoon just as we were warming up the 277 for the 1430 Rarep, the duty observer Alan Rolfe and I were attracted to the teleprinter on which the bell was ringing non-stop. It was Charleville in a 'begging mode

Apparently the balloon had decided to set ' off in a North Westerly direction from them and was fast disappearing off the end of the range scale. By sheer good luck for them Alan was EXTREMELY good at following a poor signal target. They gave us their calculated reciprocal of the package direction bearing in mind our relative positions along with their estimate of the range FROM us. The 'old girl' was in a generous mood and was going extremely well that day. Alan got on the job and searched for this elusive target, found what might be it and kept me busy racing back and forth to the teleprinter to pass our 'readings' and letting them calculate whether or not we were fooling ourselves. They decided that we had got it although to call it a weak signal was over-rating its value several fold. Alan followed it as it slowed to a stand still and slowly drifted back towards Charleville over the next three-quarters of an hour. Eventually they let us know that they thought it had re-appeared on their A Scan and in conjunction we tracked it until they were sure they had I got it back'. Once it was firmly in their grasp we heaved a sigh of relief and hastily did a RAREP and sent a covering note explaining why it was late.

I suppose it did demonstrate what a 277 could do in the hands of a good operator.
NOTE: A RAREP (or radar report) is a text version of the radar display which was sent out regularly by each radar station.

Radar Plugs - Reg Carter
Letting my poor brain "wander lonely as a cloud" over the years and gears that I have known, a "feeble ray of memory struggled down between the gaps" I wonder if anybody can remember much of the "Inter-service Colour Coding System" for radar plugs.
It was intended to be used on mobile radars where some unsuspecting tech' might find himself confronted with a radar he had never heard of let alone seen. The main users were of course the RAF and the RN since most Army radars stayed within a Unit, whereas aircraft and ships wandered about the world.
The idea was that most of the coaxial cables in a radar would be 'colour-coded' to indicate the sort of signal/pulse they were carrying. This did at least enable the tech' to know what sort of signal he should be getting on that particular output socket.
Remembering those dreadful PYE plugs, so beloved by the TRE, where you could never find a screwdriver small enough to tighten the 'grub-screw' locking the centre conductor of the coax in place. There was a coloured ring placed round the socket and a coloured band on the cable as near as possible to the plug.

The ones I can still remember are;
PYE Blue A mid-blue which indicated a "pre-trigger pulse" for example 'Early trigger' a la WF44. Could be either polarity and any amplitude but was at p.r.f.
PYE Violet-purple Used to indicate "transmitter trigger". Was always +50 volt and 20 usec wide.
PYE Green Receiver video output unprocessed and always +ve going.
PYE Orange Main display unit timebase waveform - again unprocessed.
PYE Orange/white Processed timebase waveform. Example would be the sine/cosine values of the timebase waveform sent back from the resolver in the scanner to give a PPI display.
PYE White Cal pips - if generated externally to the main display unit (I think).

I would be interested to know if any other OLD tech's can remember them and add to the list.

RAF Equipment that I know used the code besides the old 277 were; H2S MK 2, 3G, 4A, Monica, Rebecca MK2, Orange Putter, ASV7, also AI Mk VI and VIII.

(1) Numerous Bureau technical staff - 2001-2002 (private communications)

Elevation meter Photo showing PE's Iso-echo Unit