CATS Whispers Editor : Steve Beal, G3WZK Email Address for Contributions: [email protected]
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COULSDON AMATEUR TRANSMITTING SOCIETY G4FUR M1FUR CCAATTSS WWHHIISSPPEERRSS June 2012 Affiliated to the RSGB CATS Committee Chairman: Glenn Rankin, G4FVL Secretary: Steve Beal, G3WZK Treasurer: Steve Conway, G7SYO Members: Stuart Barber, G6CJR Frank Emery, G3ZMF Dennis Noe, M0NDJ James Flint, G0SDB CATS Whispers Editor : Steve Beal, G3WZK email address for contributions: [email protected] Regular Society Meetings These are held on the second Monday of each month at: St. Swithun's Church Hall, Grovelands Road, Purley, Surrey, CR8 4LA at 20:00 to 22:00 Society Nets 1st Saturday of month - 17:15 - Crescenta Valley / CATS Net on Echolink/ GB3NS Sunday mornings - 11:00 - Call on 145.400 MHz ± QRM Sunday evenings - 17:00 - Call on 3.700 MHz ± QRM Wednesday evenings - 21:00 - Call on 70.425 MHz CATS Website www.catsradio.org Email [email protected] Forthcoming Meetings Monday Jun 11th Micro DF Hunt by Dennis M0NDJ Monday Jul 9th Natter Night Monday Aug 13th CATS Barbecue at G4RWW QTH CATS is twinned with the Crescenta Valley Radio Club Glendale California USA www.qsl.net/cvrc 1 the pub for refreshments. Basic methods can CATS May Meeting include: • taking bearings and plotting them on a On May14th, CATS member Terry G4CDY map, gave other members a fascinating talk about • heading off in the direction of the strongest Direction Finding (DF), ranging from its earliest signal, or military use to present-day practice, where it • following last year’s winner! has in many places become more of a family activity than any other aspect of amateur radio. The general technique is to get three good bearings and plot them on a map. In a perfect Development of DF first began around 1900 world, the three plots would intersect at a point, and during WW1 it played a decisive part in but in practice they will form what is known in British Royal Navy’s success at the Battle Of DF circles as a “cocked hat” – smallish Jutland. Between the wars it was also triangular area. developed as a navigational aid for both aircraft and ships, mainly using LF or MF. In Equipment required will include a simple WW2 the Huff-Duff system proved to be handheld radio - although modern types are extremely successful in the Allied campaign likely to be housed in a plastic case, as the against U-boats. It enabled a bearing to be lack of RF screening will cause overload obtained almost instantaneously. problems when operating close to the Fox. Also required will be an attenuator; map, Amateur DF began in the 1930s. Antennas in compass, ruler and pencil; and a directional use include directional systems such as ferrite aerial such as a yagi, simple loop (perhaps rods and the well-known tape measure yagi; with an added “sense” aerial), or tape measure homing methods such as the “Singing antenna. Antenna” – basically two side-by-side vertical dipoles with rapid electronic switching between Terry then demonstrated a DF receiver he is them at a 1 kHz rate; or Doppler systems using currently developing. It is based around a chip 4 or more aerials with synthesised rotation – that has an operating range of between 80 and often at a rate of 10,000 revolutions per 900 MHz, making it ideal for use on both the second. Visit the following site for more 2m and the 70 cm amateur bands. Sensitivity information: is -122dBm and the output is an audio tone than varies with signal strength, although Terry www.utaharc.org/rptr/ark_df_desc.html plans to add a bar graph indicator for crude signal strength indication. The device also The modern sport of ARDF (Amateur Radio includes a 10mW transmitter, making it ideal Direction Finding) has three main areas: for additional use as a Fox. National and International DF competitions may last as long as two or three days and involve 3 or more foxes. These tend to take place mainly on 2m or 80 m and competitors receivers are quarantined before the start, to prevent cheating. Competitors start at intervals and only received their own receiver at the pre- allotted time. Fox ORing is basically orienteering with radio DF. Competitors have to use map-reading skills to get within range of the Fox. Transmitters are very low power and can generally only be received up to about 100 metres away. Club DF Hunts employ a protocol where the The G4CDY prototype DF receiver Fox – often located in the car park of a pub - (G7SYO photo) typically transmits for a period of 30 seconds After a break, everyone was invited to take part every 5 minutes. There is a set time limit to find in a mock table-top DF hunt. Bearings were the Fox – after which everyone goes back to supplied and had to be plotted on an Ordnance Survey map. Modesty forbids CATS Whispers 2 from reporting who found the hypothetical Fox fuel leak! This could have spelled disaster, but first – but it was located at Redhill aerodrome! fortunately he was able to make quick and See image below. effective repairs and deliver the “genny” to site on schedule. The CATS generator undergoing emergency repairs at the QTH of Glenn G4FVL (G4FVL photo) G3WZK’s plots – showing the hypothetical Fox to be on or near Redhill aerodrome Set-up began around midday and before long three masts had been erected along with tents, Overall this was a most entertaining and the now fully-functioning generator and other informative evening for all the CATS members Amateur radio essentials, including a barrel of who turned up. Thank you Terry! homebrew beer kindly provided by CATS Chairman Glenn G4FVL and christened “The Chairman’s Brew.” G0KZT Radio Play Day G0KZT Radio Play Day Aerial wise, we had a good number of aerials to play with including two HF verticals, two The idea for this event was conceived by Andy The idea for this event was conceived by Andy Windoms, the club’s 17 element Tonna for 2 G0KZT at the beginning of 2012 as a fun G0KZT at the beginning of 2012 as a fun metres and the 19 element Tonna for 70cm, weekend during which members – and guests weekend during which members – and guests collinears covering 4m, 2m, 70 cm, and a 3 from other clubs – could have fun with amateur from other clubs – could have fun with amateur element beam for 6 metres. CATS member radio. It was hoped that the more relaxed pace radio. It was hoped that the more relaxed pace Frank G3ZMF also had a small beam on 23cm – compared with contesting – would encourage – compared with contesting – would encourage and used a TS2000 kindly loaned by Terry non-contesters to come along and join in with non-contesters to come along and join in with G4CDY as his own TS2000 was faulty. whatever aspects of the hobby they enjoy. whatever aspects of the hobby they enjoy. The location – a new one for CATS – was on a hilltop in Paddock Barn Farm, just off the A22 near Caterham. Use of the site came about thanks to a suggestion from CATS member Denis M6XLS, who is friends with the owner of the site. Fingers were crossed as the proposed weekend for the event drew near. April was the wettest on record and things were looking doubtful until the Tuesday before the event when temperatures started to rise … and just kept on rising. As the Friday dawned there was a clear blue sky and a daytime max of 24C. Things were looking good! Andy G0KZT begins assembly of the CATS 17 element yagi But then, just before leaving home, Glenn for 2 metres G4FVL discovered that the generator had a 3 CATS members who attended to help set up (and dismantle) or operate included Andy G0KZT, Andy G8JAC, Glenn G4FVL, Terry G4CDY, Steve G7SYO, Steve G3WZK, Len G0GNQ, Ian M3IGP, Frank G3ZMF, Stuart G6CJR and Denis M6XLS. Visitors from other clubs included Adam G7CRQ, Vince G1HRD, Alex 2E0, Colin G4CJR and his son. On-site facilities were good with plenty of space available for experimentation and, with Caterham town centre only 5 minutes away by car, it was easy to pop 0ut for a takeaway! Big thanks to Andy G0KZT and other members of the organising group. Also thanks to Denis M6XLS and his friend whose field it was. A selection of photos follows. More photos are available on the CATS page on Facebook. Other Photos L-R: Adam G7CRQ and Andy G0KZT with yagi antennas for 2m, 70 cm and collinear for 4m, prior to mating with the main mast The six metre yagi on its mast L-R: Andy G0KZT and Adam G7CRQ with yagi antennas for 2m, 70 cm and collinear for 4m mated with the main mast On the Friday evening I operated the station of Len G0GNQ while he left the site to get a take- away. The ten metre band was wide open with stations coming in from several South American countries including Argentina, Brazil and Chile. On the Saturday I operated mainly on 2m SSB but also had my first ever QSO on 4m, despite having been licensed for 45 years! Andy G8JAC’s operating position overlooking the Caterham So I certainly had a lot of fun and did valley – the vehicle is an Austin Champ with trailer something new, too! 4 G3ZMF Corner Andy G8JAC on the Saturday morning VMARS net Frank G3ZMF puts the finishing touches to his experimental home-made vertical for 20 metres The CATS antenna farm, early on the Sunday morning. The homebrew 20 m vertical of G3ZMF is nearest the camera, next to his tent.