Club Call G4HRS Est. 1938 The Journal of Horsham Amateur Radio Club April 2021 Sponsored by: Affiliated to: 1 Contents In this issue 3. Notes from the Editor A radio amateur opinion 4. Hush... don’t tell anyone A story about secret codes 8. Rigs anonymous Calculate the quiz answers! 10. Slow pictures A very long weekend of on air entertainment 21. Fast scan A disappearance and a visit to North London 26. Diary of events Full listings for the month Cover photo: Colossus Published by Horsham Amateur Radio Club HARCNEWS is produced at home by G4JHI 2 Editorial This month is a TV special, Slow Scan and Fast Scan! We have the video presentation talk report about Top Secret Cipher held over Zoom, details on what happened over the recent SSTV weekend, a top specialist in making exciting technological items out of cardboard and a quiz to really make you think! I spend a small amount of time each week doing online surveys as mentioned before in this column. A new survey ‘RAOLS’ (Radio Amateur Operating Listening Survey) has come out in which radio amateurs can take part in. This will include questions about your radio listening and operating habits. As an example, the survey may include questions such as: How many times do you sneak away in the middle of the night to your shack to look for DX? How many transmitters do you own? What is the feeder length connected to your antenna? What is the colour scheme inside your shack? Do you own a USB cable? To take part all you need to do is to have read the above by the first Thursday in April 2021 and those selected will receive a link to the survey. David G4JHI Copy deadline for emailed items for May edition 20th April - For hand written items the deadline is 12th April. For items sent by email please send to this address: [email protected] N.B. Documents sent for publication may be edited for reasons of spelling, grammar, duplication and occasionally other reasons Copyright material will not be honoured unless evidence from the author is produced showing permission has been granted for the material to appear 3 March Online Talk: Breaking Hitler's Top Secret Cipher, by Andy G8TJQ, assisted by Phil M0PIT Andy is a Director and Trustee of the National Museum of Computing (TNMOC) on Bletchley Park and Phil is the Chief Engineer of Colossus. In WW-II there were about 40 Y-stations which intercepted radio communications and some could direction-find the transmitters. They were critical in giving Bletchley Park something to work on. The HQ was Beaumanor Hall, near Leicester, and the outbuildings there were camouflaged as cottages, barns, stables, chapel and a cricket pavilion. Pneumatic tubes sent messages from building to building to reduce foot traffic which could be spotted by aerial photography. BP was discovered by a 'shooting party' as somewhere with good communications as roads, rail and a main GPO telephone trunk cable were near. The code-breaking was performed here. The first target was Enigma messages. Enigma machines had 3 or 4 rotors and were used in the field to send tactical information. The second target was from the Lorenz machine, code-named FISH, and first heard in June 1940. Code wheel detail 12 wheels from a Lorenz machine An Undulator machine traced the signals on paper tape called a slip. This machine had 12 rotors and transmitted an RTTY-like signal as 3 tones using Baudot code, which saved radio operators having to manually key in and receive Morse code as with Enigma. Undulator – Photo Courtesy G8TJQ 4 Only the highest grade traffic was sent via FISH. Strategic traffic was sent to/from Berlin through links such as Vienna to Athens. That link was code-named TUNNY. Other links all had different fishy codenames. FISH used Vernam encipherment where a key was exclusive-ORd with the text. This was considered impregnable. Luckily for us, an operator on the TUNNY link hand- typed a four-thousand character message on 30th August 1941 and the other end asked for a repeat as they missed some of it. So he reset the rotors on his Lorenz machine and started typing all over again, but he abbreviated some words e.g. 'SPRUCHNUMMER9' to 'SPRUCHNR9'. The net result of that was the second message was 500 characters shorter, thus giving Bill Tutte an insight that enabled him to successfully reverse engineer its design. One interesting aspect of the exclusive-OR function is that some information about the key may be gained by exclusive-ORing the two enciphered messages. Bill Tutte was asked to reverse-engineer the system from these two messages; he sat at his desk for 3 and a half months staring out the window, thinking... He worked out that it should have the 12 rotors with a different number of possible positions: 43, 47, 51, 53, 59, 37, 61, 41, 31, 29, 26, 23. The TUNNY machine built at the Post Office Research Station at Dollis Hill was the direct electrical equivalent of the Lorenz allowing the decryption of FISH traffic once the Lorenz wheel start positions were known. This machine used uniselectors and plug boards. Meanwhile, Max Newman commissioned the design and manufacture of a machine called Heath Robinson which ran two paper tapes in loops, but it was unreliable and the tapes stretched and broke. In spite of that, people could take two or three months to get the rotor settings. This machine could reduce that time to 6 days. As the traffic was strategic, it was still valuable to get into the mind set of the Fuhrer and know of his long-term plans. Heath Robinson demonstrated that the principle of the machine was sound and that led to the design and building of the Colossus by Tommy Flowers. Colossus reduced the time to find the Lorenz wheel settings from typically 6 days to 6 hours. Tommy Flowers, the GPO's senior research engineer, came up with the idea of using valves to emulate one of the paper tapes. 2,500 valves were needed and it was considered by many that they would not be reliable enough. Tommy realised that if the valves were run continuously then there would not be a problem. His machine Colossus was finally working one Sunday in January 1944. It reduced the code- breaking time to 6 hours, and was used in particular to make sure that the real site of the D-Day landings was hidden by deception. 5 Kesselring's machine was taken to England after the Nazi surrender, and now lives near Cheltenham. Captured Lorenz machines were retrieved and taken to England after the Nazi surrender; one is on display in the TUNNY gallery at TNMOC complete with an original operators’ teleprinter and code setting board as used during WWII. The Lorenz company used to build teletypewriters to U.S. specifications, and must have had a large stock of U.S. threaded screws; they never bothered to switch to Metric! The Colossus Rebuild Project A project was started by Tony Sale in 1993 to rebuild Colossus. The machine ran on 6th June 1996. Its optical tape reader ran at 5,000 characters per second, and it had 501 Thyratron valves plus the usual suspects 807, EF36, EF37, 6V6 etc. The Mk2 version was completed in 2007. The gallery was rebuilt in 2014. Obtaining enough valve bases has been a problem and many are custom-made, but the Araldite is showing its age and caused issues. Valves in Colossus 2007 Cipher Challenge A plan was made to lend the Lorenz machine to the Heinz Nixdorf Musuem, Paderborn, Germany, and let their amateur radio club send a message which would be intercepted and fed into Colossus for decipherment. There were many obstacles on this: amateurs were not allowed to send encrypted messages, one could not export cypher equipment, insurance was 'difficult' to get when only 4 known machines exist, and sending the 3 tones for mark (900, 1,620 and 2,340Hz) and space (540, 1,260 and 1,980Hz) at 45-50 Baud not easy. Anyway, these issues were all overcome and on 15th Nov 2007, DL0HNF sent the message out on 80, 40 and 20m. Colossus took four and a half hours to get the wheel start positions. But the winner was Joachim Schueth, who took 59 seconds! He subsequently went to BP to collect has trophy and gave a speech written by his parents. They thanked everybody who worked at BP or was involved in intercepting messages because it ended the war an estimated two years earlier than would otherwise have been the case, and allowed them to get on with their lives in peace. 6 Colossus Maintenance TNMOC has to pay substantial rent and utility charges to its landlord and can’t afford the electricity bill to run Colossus all the time as in wartime. Two 3.5kW motorised Variacs are used to gradually power up the valves so there is less thermal shock. There are about eighty 807 valves, and each one resets a bank of Thyratrons. Unfortunately the 807 is subject to a heater to cathode internal short-circuit failure mechanism, and if more than one fails, then spurious resets occur. So the Museum is always keen on supplies of valves in order to keep Colossus in fully-working order. Thanks to Andy and Phil for giving us an excellent talk. We look forward to being able to have a day out soon and visit both BP and the Museum.