OPEN UNIVERSITY AMATEUR RADIO CLUB
NEWS LETTER no:26
G0OUR Affiliated to the OU Club and the Radio Society of Great Britain
If there is a red cross at the top of this newsletter it indicates that your subscription for 2001 has not been received. If so, your continued support of the club would be much appreciated. Subs remain at five pounds per anum. Cheques payable to OUARC should be sent to the Treasurer, Fraser Robertson, S1021 Venables Building, OU, MK7 6AA.
This years AGM was held on Thursday 11th January 2001, and we had a good turn out with twelve members attending. Congratulations to Jeff Walsh on passing his novice exam and receiving his certificate on the morning of the AGM. He is now 2E1OUJ and the proud owner of a Yaesu FT100 radio. Jeff was featured in the OU staff newspaper 'Open House' with a colour photo of him in the club shack. Also congratulations are in order to members who have recently been granted planning permission for their aerials: Linda & Les (M0CMK & 2E1EOT), Bert (G3FVO), and Tony (G0LAX).
Along with other OU clubs we have been asked to support 'Learning at work day' which is on Thursday 17th May. We hope to have the shack manned for at least part of the day to demonstrate the hobby and give information to any interested visitors. We would be grateful for volunteers able to help on that day. Contact Adrian for more details, email: adrian@euroneta.com
We have booked a pitch for our first 'boot sale' of the year, which is the DDRS sale at Stockwood Park, Luton on Sunday 13th May, and any help with that will be appreciated. Last year we raised over £450 from four sales, so it is a very worthwhile activity for the club. As usual we have plenty of junk to get rid of!
Towards the end of last year we upgraded the CW filters in the clubs IC756. We now have a pair of 400Hz Inrad filters fitted, which give a big improvement in skirt selectivity over the stock Icom 500Hz filters. We were able to sell the Icom filters to offset the cost of upgrading. The 80m sloper was completed in January and does a good job, on occasions giving a couple of S-points improvement over the 80m dipole on DX contacts.
The club was able to work the recent D68C DXpedition to Comoros on 9 band/mode combinations, and four members worked them from the club using their own calls too. D68C was a British organised trip which was active between 8-28th February and made an astounding 168,731 contacts in the three weeks, breaking many records along the way. Their web pages at http://www.dxbands.com/comoros/ make interesting reading.
We now have a counter (written by club member Ian G0TLB) on the clubs web page, which shows about a hundred hits in its first month. Adrian was informed that a link to our website has been added to: http://hamgallery.com/links/clubs/G/. Hamgallery contains a wealth of information and links including: A large Ham Photo Gallery of Hamshacks, Ham Collectibles, Antenna farms, DXpeditions, DX locations, Contest Stations, also over 250 Rare DX sound clips in Streaming Real Audio format, Free Ham Classified Ads, 100 Most Wanted Countries Archive, Morse Code Tests (13 to 65 WPM), Webclusters, access to 24 DX Telnet sites, QSL Card Gallery, DX News, Propagation Bulletins, and Ham related news bulletins, Search Engine Page, the list goes on...
At the AGM Tom Mitchell G3LMX gave us a report of activities at Bletchley Park (BP), where MKDARS are based. He said they are now are a registered examination centre for the Novice Exam, the RAE, and the Morse test, as well as running courses on each of these. Half of BP has been sold for development and MKDARS' activities need to be relocated. The BATC rally will take place on 6th May, and MKDARS boot sale on 26th August, both at BP. Also the RSGB are holding a rally at Bletchley Leisure Centre on 7 & 8th April which MKDARS are stewarding. MKDARS meet at BP every Monday evening at 7.30.
The licence to go ahead with the new car park extension was granted on 12th March and work is due to start in the next few weeks, for completion in July. As a result we have moved two of the elevated radials for the 80m sloper, and the 160m receiving loop. Ducting work is currently underway which will link the Security Lodge with Park Corner Cottage and ultimately the bungalow where we are being relocated to. This will carry cables for power, security cameras, data network and telephones. The Security Lodge extension is due to start at the end of March, also for completion in July. Plans are still underway to relocate users of the field site, and we are still negotiating this. The bungalow at the new site has been secured and its garden cleared. A burst water main was discovered which accounts partly for why the garden was so wet! Unfortunately just after the OU had the area cleared, it was taken over by 'travellers' who have turned it into a rubbish tip. Steps are being taken to improve security there.
The packet node continues to give good service in the main. The Didcot link failed recently and after tests at both ends the problem was traced to an aerial fault at the Didcot end. Our beam to Bedbox ended up in a rather odd position after a recent gale, but was quickly sorted out by Ian G0TLB. Currently the fast link to the GB7DXI Cluster from Didcot is out of action due to a radio fault, and the most reliable Cluster access seems to be to digipeat through G3BJ on the 2m port. A request was made at the AGM for the OU node frequencies to be published in the newsletter. They are as follows:
6m 50.67MHz Horizontal, link to BY (GB7BEN) in Bletchley
4m 70.325MHz Vertical, user access and (poor) link to AYLS4 (G3BJ) Cluster node
2m 144.900MHz Vertical user access (omni directional)
70cm 433.675MHz Horizontal link to Didcot
70cm 434.225MHz Vertical 9k6 link to Bedbox
The last video was from Secret War - World War 2 Series 1991 - 1, Battle of the Atlantic, on Thursday 14th December. This contained interesting snippets on the development of radar. The next video is by ON6TT and covers the 1997 Dxpedition to Heard Island - VK0IR. It lasts for 53 minutes and will be shown starting at 12.30pm in N2028 Venables Building on Tuesday 24th April. We have avoided Thursday by popular request! Everyone welcome.
Frank G3ACT was asked to write a little about his background in radio. His story is very interesting and didn't lend itself to being easily split, so as a result this newsletter is running to a record three sheets of A4. We would welcome contributions from other members, even if it's just a few lines. So here goes with Frank's tale:
CATSWHISKERS TO MAGNETRONS.
My interest in Radio, Wireless as it was called at the time, was aroused in 1929/30 when I joined Sir Tomas Rich's School at Gloucester. The physics master at school was an early licensed Radio Amateur and had been involved in radio communication in the Royal Navy during the First World War. As an after school activity he encouraged we boys to construct crystal sets moving on to valves as we gained knowledge and experience. The Headmaster strongly disapproved of this activity considering that our time would be better spent in improving our minds in concentrating on our homework. As he was a Cambridge MA Classics man, and also a MD, he expected us to eventually matriculate and move on to Oxbridge to become classics students. I think that the only reason he tolerated the extra mural radio activity in the Physics Lab was because his son was a radio enthusiastMy interest in radio continued for a further seven years during which time I made useful pocket money building receivers for friends and family. This entrepreneurial activity began to wane when reasonably priced manufactured radio sets began to flood the market. (Where did all those pre-1939 radio manufacturers go?). I did not matriculate (who needs Latin anyhow?) but I was accepted as a Trainee with one of the leading radio manufacturers when I reached the age of 18. The training I did receive both in "steam radio" and television was very comprehensive, additional experience being gained when I joined the firm's Amateur Radio Club. We trainees were not only encouraged but also expected to join. I received tuition in the use of the Morse code from an ex-Navy Petty Officer telegraphist and with the support of the firm I was granted permission to operate the Club's rig in the CW mode only, so becoming an active Amateur late in 1938. I was almost fired from the firm when I was alone in the clubroom operating the rig when the Director of TV Research burst into the room and told me to close down. It seemed that every operation of the Morse key caused the picture to jump through the screen on the set the TV Director was demonstrating in the Laboratory to the Duke and Duchess of Kent. Could I therefore have been the first Radio Ham to cause TVI?
When the Hitler War started, despite the fact that I could have been reserved in my job, I joined the army requesting a posting to the Corps of Signals but in the event I found I was in the Royal Artillery as a Gunner Trainee. (This was not unusual, trained plumbers were often cooks). After serving a hair raising couple of months in the Norwegian campaign in early 1940 my records caught up with me and I was sent for training on "military radio equipment" as it was called without further description. Incidentally, the move was a lucky escape because I learned later on in the war that the Unit I served with in Norway had been involved in the battle of Crete and were all lost to a man as casualties and prisoners or war.
I discovered that before I was to receive training in this "equipment" I was expected to pass an examination in general radio theory. This took place at Coventry Technical College where a group of soldiers and civilians were given the run of the college library and a copy of the syllabus upon which we were to be examined and told to prepare for two three hour examinations. We were in the charge of an Army Major who instructed us not to "arsey tarsey about" but get on with it if we intended to move to the next stage of our military career. We were left almost entirely alone to get on with our swotting apart from two mornings when we received lectures, from the Major, on the subject of HF, VHF and UHF aerial theory and applications. Fortunately, I somehow passed the exams, which were at the level of the Higher National Certificate.
The next stage of this training took place at the Radar Wing of the Anti-Aircraft School of Defence. So I now knew what I was getting in to. This establishment was located at Watchet in Somerset. The course was to take around four months to complete and was conducted very much on University rather than military lines apart from the compulsory Sunday Church Parade. The Instructors had been recruited from the Universities and the Radio Industry with a minority of Military NCO's and Officers. At the time Radar was cloaked in a shroud of secrecy and we had to sign the official secret act and were threatened with the prospect of facing a firing party if we breathed a word about what we were doing there to outsiders. A few weeks later the national newspapers carried stories about the new wonder weapon, Radiolocation.
The significance of the lectures on aerials at Coventry was now revealed because the gun and searchlight radar control equipment operated on a range of frequencies from 60 to around 300MHz all of which employed Yagi aerial arrays in one configuration or another. The gun control radar at this time, 1940, consisted of two mobile caravan type trailers one containing the transmitter unit and the other was a rotating cabin containing the receiver. The operating frequency of this gear was in the 60MHz band which was one of the reasons the Alexander Palace BBC television station closed down in such indecent haste on September 3rd. 1939.
This early gun control radar was an early warning device but also capable of measuring azimuth and range of aircraft. Azimuth was measured by means of two horizontal half wave dipoles wired in anti-phase and when a reflected signal was received an operator rotated the cabin until the signal on the display cathode ray tube was at zero, which was the point at which the signals from the two anti-phase aerials were equal and therefore cancelled one another. These two aerials were at about one and one half a wave-length apart and about a half wave above the ground. The range dipole was a single half wave dipole located about three quarters of a wavelength above ground so as to produce a lower angle polar diagram pattern. In front of this dipole was a switched reflector so that when it was switched the signal would reduce in amplitude so that the "sense" of the bearing could be determined so avoiding an error of 180 degrees in the measurement. (There were times in those early days when careless Radar operation resulted in the guns firing in the opposite direction to the approach of the target aircraft). The IFF, identification Friend or Foe, system was introduced at about this time which caused the radar signal to trigger the IFF transmitter in the aircraft so producing intermittent 'blips' to appear alongside the signal on the radar screen being received from the friendly aircraft. This system was helpful if the pilot of the aircraft remembered to switch on the IFF gear. He was, however, reminded of this when shells began to burst around him.
The weakness of this radar was its inability to measure the actual altitude of aircraft. This information was essential to the Gunners in determining the correct elevation of the guns and the setting of fuse lengths. Initially, altitude was measured by artillery range finders which calculated height as a function of range vis-a-vis angle of sight. This was only possible, of course, during the day when targets were visible or when illuminated by searchlights. During 1940 the problem of angle measurement was solved by the development of a further array of half-wave dipoles. This consisted of two dipoles, one above the other, the lower one at about a half wave above the ground and the upper one at about three quarters of a wavelength above the ground. The signals received by these "angle" aerials were fed each into coils within a goniometer but due to the different heights above ground of these two dipoles the received signals which were reflected from the ground to the dipoles were at a different phase from each other. The coils in the goniometer were fixed at 90 degrees with a rotatable coil in close association with them into which the signals from the fixed coils were induced. The rotating coil was operated until a zero signal was produced its physical position depending upon the phase difference of the signals produced in the coils. The rotor position was calibrated in angles from zero to ninety degrees. This information therefore enabled altitude to be calculated. e.g. At a range of 20,000 feet at an angle of 30 degrees, the altitude would be 20,000 x O.S(sine 30) = 10,000 feet. The aerial systems of this early type of radar made it almost immobile, particularly since accurate angle measurement was dependant on a flat, level and homogeneous surface around the receiver unit otherwise the phase differences in the two angle aerials would be affected so producing an inaccurate angle of sight. This problem could only be overcome at permanent gun sites by building a large area of wire netting around the radar receiver to ensure a flat and level reflecting surface.
After service in the London area with an anti-aircraft regiment dealing with radar siting problems, first line maintenance and the training of operators, I went in 1943 to North Africa and later Italy dealing with gun control radar in a mobile role which was very unsatisfactory in that the proper siting of 3.7 inch anti-aircraft guns and radar was infrequently incompatible as the radar did not always stand up to having aerials dismantled and reassembled, also at times the spares situation became difficult. However, with experience the radar teams and the gunners did a very good job particularly immediately before the invasion of Sicily and Italy when we had to deal with very heavy air raids at the Algerian and Tunisian ports where the allied invasion fleets were being assembled.
Those who have any experience of the Military will know how rumours arise and quickly spread. I had heard whispers that a new revolutionary Radar had appeared somewhere in North Africa, likened to Noah's Ark when compared with the Queen Mary. So, lo and behold I was not the least surprised when I was ordered to report to a location near Tunis to spend a week becoming familiar with a new piece of equipment. When I arrived at this very closely guarded location I observed a large cabin shaped trailer covered by a camouflage net. Closer inspection revealed that this trailer had two parabola dish shaped objects on its roof, which someone inside the trailer was causing to rotate and elevate. This was the No. 1 Mark 3 gun control radar unit.
The Mark 3 housed a complete radar station. Having both the receiver and transmitter together required the employment of only three operators whereas the previous radar of my experience required four operators in the receiver and one in the transmitter unit. The transmitter was situated in a cylindrical shaped housing which together with the two dishes above it on the roof was remotely rotated in azimuth and elevation by one of the receiver operators. The rotation of the whole transmitter unit avoided slip ring connection losses to the aerial system which would otherwise have been a problem had the feeder connections from the rotating aerials been via slip rings particularly as the transmitter power was many kilowatts at peaks. The front-end stages of the receiver were also housed in the transmitter unit its output being fed to the receiver displays. One of the aerial dishes served the transmitter and the other the receiver. Later marks of Radar had only one dish being electronically switched from the transmitter to the receiver- units in turn during the gaps in the pulsed transmission. The operating frequency of this equipment was around 3GHz, a low frequency when compared with those in use today. There were three receiver displays, the first was a Plan Position Indicator (PPI), the second measured bearing angle and the third indicated the range. The angle and range measurements produced an instantaneous altitude reading The polar diagrams of the dish aerial were, in theory, very narrow so that this Mark of Radar was not a good search and early warning device. Therefore it was necessary for the earlier mark of Radar to be used to guide the Mark 3 on to the target. However, an operating block search drill was devised but this was time consuming. The accuracy of these radar's was such that when used as a gun laying aid via the new electronic predictors and the use of proximity fuses, a large number of flying bombs destined for London were shot down by the gun batteries located on the East coast of England.
Soon after making the acquaintance of the Mark 3 my unit was shipped over to Italy by which time enemy air activity became almost nil, making Anti-Aircraft Artillery redundant in that field of operations and my regiment was assigned to a Field Artillery role. In the event of the enemy resuming air activity the older Mark of Radar remained with the guns but later removed and the Radar operators were employed on the guns, and spent about a month carrying out observation post duties visually guiding gunfire from the batteries in our rear. This occupation is not to be recommended. I was withdrawn from this duty and ordered to assist in setting up a Training Unit to upgrade Radar operators in the operation of the Mark 3, which started the rumour that the training would be for duty in the Far East. After a very enjoyable time at this training unit which was located on the hills above the city of Florence I was given the job of taking the Mark 3 mobile with a group of operators to provide meteorological information to the HQ of the Allied tactical Air Force in Siena. This involved inflating large balloons, attaching silver surfaced reflectors to them, releasing them and following them by the radar. Calculations were made of the plots to provide information of the windspeeds and directions. This was coded and sent by radio to Siena by a Royal Signals operator attached to the Unit. Just after Christmas 1944 I received shipping orders to proceed to the UK to attend a course of instruction to be held at Manorbier in Wales. Once again the rumour was that fate awaited in the Far East after the course. In the event, after a course on American made Radar I was attached for the remainder of my army career to the Ministry of Supply Electrical and Mechanical Inspectorate. This duty involved visiting Radio Manufacturers in the London area to ensure that the radar components being produced satisfied the specifications. This work continued until after VE and VJ days and I was demobilised in January 1946.
In 1946 I was among the first group of G3 Amateur Stations to be licenced since 1939. I was active until around 1951 when work pressures made it necessary to put my licence into cold storage. I resumed my Amateur activities in 1980 when I retired.
That's all for this time. Please send any news items or 'member profiles' to Fraser for inclusion in future newsletters.
73 for now...
Contact: Adrian Rawlings adrianrawlings@googlemail.com