All posts by G4YRF

26 Sept 2019 – Use of SDR by Alan, G4PSO

Alan gave a talk on the uses of SDR based on his experience to try and get a weather station to work correctly.  The method chosen was to use GNU to help find the frequency used by the weather station and eventually see if he could pick up the data from the device.

He explained how the GNU programme could be used to see different o/p and represent them in various forms an example was a 1 KHz audio signal o/p and an oscilloscope giving a sine wave of the out put.  The programme uses various elements, which are selected to make the programme do what you want to do.

Alan had used several types of SDR in his experiments and he demonstrated how the signal from his weather station was represented on the waterfall screen. It was noted how members activation their car keys could also be picked up showing how wideband the SDR was.

Alan had used the Funcube dongle, the HackRF and other SDR dongles to help him find out about the weather station.  He pointed out that a shortcoming of  amateur SDR equipment was the sensitivity which can be overpowered by strong RF signal.

An interesting and different evening.

Report by David, G8UOD

12 Sept 2019 – Welcome Back after the Summer Break

We were 10 in number. Tables were set around with chairs and tea and biscuits were quickly on the tables. Gary M0PLT spoke about being mobile on his bike and using APRS. Another subject discussed was FT8 and FT4. Victor, G3JNB, made the point that if it were not for that mode the airwaves would be quiet. Gary, M0PLT, mentioned that he had exchanged details using FT8 into Australia.” There was quite bit of discussion, before closing at 21.30 hours

Report by Paul, G1GSN

19 Sept 2019 – The visit to Baldock Radio Station

Members were given a warm welcome and we had a warm drink and were shown some photographs of the installation before we got going.

The site has had some alterations this year and this was an opportunity to see how things have change since our last visit.

Our starting point was the technical area where equipment can be checked out and worked on. This was followed by a visit to the anechoic chamber, designed for testing equipment. Built to prevent both sound and RF from interfering with test items.

The next part of the station was the measuring and testing laboratories, where various specialised equipment are used, such as Vector Signal Generators and Spectrum Analysers. These are used to put radio equipment under test to make sure they meet the required specification. Here we also found portable monitoring equipment used to check mobile phone equipment. The equipment can test radio equipment from DC to 57 GHz, for 5G communications.

There was a visit to the Drone laboratory where we saw a large drone, which can be equipped a spectrum analyser to help locate interference. The drone is equipped with GPS locators to help with DF functions. Users of this equipment have to pass a CAA test before they can fly the drone.

Our next stop was in the Control Centre, a suite of radio equipment designed to monitor the airwaves from DC upwards. The centre is divided into two parts one to monitor safety and life support communications and the other for commercial and amateur communications.

We were given a real life experience when the unit was contacted because there was interference on a safety circuit. We watched them start a trace using SDR equipment, which can find direction of signal, its angle of reception and the bandwidth. We could actually hear the interference on top of the original signal..

The station also looks for Band 2 pirate stations as well as distress signals. Satellite systems can also be monitored. All the signal come into a labyrinth of aerials which are spread over the site as well as some which are in remote locations. The antenna systems include a circular array of 16 aerials, similar to the old Chicksands antenna system. This gives a very good DF location for signal from DC to 3 GHz.

Our very interesting evening came to a close about 21.00 hours, where the usual thank you was made by club members and a couple of other visitors.

All in all a very interesting evening.

                      Report by David, G8UOD




22 Aug 2019 – Military Intelligence Museum Visit

The introduction

Members of the club congregated in the arrivals area of JIC ready to book in and get parked up for a 10.30 start.

Bill Steadman gave us an overview of the site and museum before going in to meet our two guides David and Tim.

We were split into two groups due to the numbers. The first group went off with Tim to visit the Photographic reconnaissance part of the museum, whilst David explained to the other group what intelligence was all about.

He went through the sources used to gather intelligence and the product that came from the sources. These included methods of gathering information such as observation, interrogation, signals, communications and satellites.These inputs would be used to assess a situation, which could be operational, tactical, strategic or technological. All combining to support a military or a diplomatic situation.

From here we went on to view the Barnard Display, which gives an insight to the operations undertaken by the SOE during World War 2. It illustrated the type of equipment that would have been dropped behind enemy lines to help set up intelligence gathering and set up or help espionage teams to disrupt the enemy. The display shows some of the equipment that would have been dropped in, including weapons, radio equipment and other important equipment to help the underground effort.

From here we moved onto a display on how intelligence was gathered at the end of the war within Germany, mainly on the Russians. The unit was called BRIXMIS and went undercover in the Eastern block to monitor what the Russians were doing. This would include the movement of men, machine and vehicles. This went on into the cold war and was used to help make intelligence decisions.

Many of the men and women who were part of the SOE did not make it through the war and there is a list on personnel who served and fell in the SOE.

From here David took us into the next room, which had many displays on the types of work carried out by intelligence groups. These displays cover the period from the Second World War right up to the Iraq invasion. It shows the type of equipment that would have been use and the uniforms of the time.

There are displays on PsyOps and the products they produce as well as the use of forensics to gather intelligence. An example being the ‘Four ☐‘ (square) Laundry, where houses of suspect IRA members were offered a laundry service, which was run by the intelligence service, who would check the laundry for explosive residue. This was used to identify locations where bombs were being manufactured.

Other displays include a Y service station, an Enigma machine and a model of the old Elephant cage antenna array used by the US Military to monitor over the horizon communications.

As we worked our way round the room we were shown the type of weapons used by the IRA to attack Downing Street. A very crude device but one that showed that sophisticated weapons were not getting into the IRA’s hands.

The next display shows how intelligence is used to give tactical information on the locations of men and weaponry in the cold war, using codes to define the strength and location of various military units, both enemy and friendly.

As we went round the displays several of them had special equipment used in various theatres of war to help gather intelligence, such things as hollow bullets to carry secret messages as well as many displays of brave soldiers who went that little bit further.

The first part of the visit took about an hour, at this point the groups swapped guides and we went with Tim to be told all about gathering pictorial intelligence.

The stereo photographical displays show how various types of photography have been used from as early as the First World War right up to present times. From the use of glass pate cameras through to charged coupled devices (CCD).

While cameras were used for capturing images in the Great War the technology was in its infancy and it was not until some pioneering officers invented new equipment, such as Captain Laws in WW1 using stereo photography did things start to improve.

Other men also improved the methods used, these include Captain Hamshaw-Thomas and in particular Sidney Cotton.

Sidney Cotton was a businessman who dealt in photography and also held a pilots licence. When the threat of war (WW2) began he was doing business with the Germans, which continued through the war. However his business at Wembley was processing pictures taken while he was flying on business over Germany.

His business was aerial land surveying and he had special equipment made in Switzerland to look at the photos. The system was the Wild A5 photographic reader, which enabled the terrain of the land to be calculated, as well as having very accurate and clear imagery.

Much of the display shows the various images taken over specific operations during the Second World War. Many of these images were processed at RAF Medmenham and can be seen on the walls of the museum along with the men who took them and in many cases the women who helped identify the targets.

As we moved on to the second room we were shown some of the more up-to-date equipment used in jet fighters and drones. On display are the cameras with examples of the images they would take. From monochrome to colour and onto infrared, as well colour separation imagery.

More recent images are collected using RADAR and video, some of which are processed while being taken.

The visit lasted a good two hours and there were seats for those who wanted to take the weight off. The visit ended with the club’s usual thank you given by Martin, M0XMP the Vice Chairman.

                                                                                                                                                                                                     Report by David, G8UOD
(L) Martin, M0XMP and (R) Ian, G3ORG inspect a Wild A5 Stereoautograph. – Photos by Alan G4PSO





11 July 2019 – RF and Earthing by Richard, G3Nii

It became apparent right from the start that Richard’s talk was not for the un-initiated. Quoting directly, Richard said:  The earth provided by the electricity supplier is intended as a protective part of the circuit to reduce SK membership, as well as protecting devices and equipment attached to the supply.  It is a very important part of the circuit that has to comply with various parameters as set out in the 17th Edition of the IEE Regulations, BS7671. The 18th Edition is now replacing the 17th, this may result in further adjustment of the earthing requirements. Over the years the way in which the earth connection has evolved and is provided has seen changes and indeed variations for different types of consumers, e.g. industrial, farming, those supplied by over-head lines and domestic users.

Richard continued with a description of the mains supply from the sub-station to the supply into the property.  He described various methods of earthing used in the past and finished with the TN-C-S system (PME) used in the majority of properties today that offers the biggest challenge to incorporating an RF earth and where extreme care needs to be taken.

Richard then pointed out a potential problem which was highlighted in an article by Peter Chadwick, G3RZP, well known for his many presentations at RSGB conventions, highlighted in a RadCom article in 1980 the possibility of a failure of the neutral  of a PME supply system  that could lead to a disastrous situation arising, a situation that can and has arisen in the past. So although a rare possibility of it happening take careful note of the consequences should it do so and the procedures necessary to avoid a catastrophe.

Many Radio Amateurs will have their RF earth attached in some way to the general earth wiring of their house mainly due to their not understanding any of the  limitations or requirements associated with doing so. It is a very dangerous path they tread.

Richard continued; So what’s to do? Do you really need an RF earth ? Insulated radials, above ground, or a counterpoise arrangement for those antennas needing an earth, both would work well. Many claim that the counterpoise is quite superior to radials  But, if you have a tower you will no doubt want to protect against high static charge build-up and electric storms thus needing an earth point close by. However, consider a lightning strike yielding 100MV and 200kA, this obviously will destroy everything in its path. A near discharge could be tolerated by a good supplementary earth point, but don’t rely on the PME earthing for this purpose.

Other things that could be done included completely isolating the shack, but that must comply with regulations, or a large isolation transformer, apart from the cost, might an answer.

More info can be obtained from the RSGB. Search for their EMC07 Advanced Leaflet titled Earthing and the Radio Amateur.









4 July 2019 – This year’s club project

Richard, G3NII explained the main purpose of the latest club project, an HF choke, is to stop common mode currents flowing on the outer skin of coax feeder thereby stopping radiation from the feeder, stopping RF from getting back into the shack and also to lessen QRM pick up on the coax feeder. Thoughts of where if should be placed indicated that since this was adding impedance to the circuit, then positioning in the shack would be worth considering – BUT, make sure the feeder is not an odd number of 1/4 wavelengths long, any number of 1/2 wavelengths long would be ideal.

Richard pointed out that the project required 12 turns of coax on the toroid. You have the choice of 5 turns then cross-over then 6 turns, alternatively 6 turns then cross-over then 5 turns. The cross-over counts as one more turn.

The kits, which included all materials required, including the box,  were handed out and members started the winding and fixing. The evening ended with a Q&A session about the choke and other antenna configurations.

The kits were supplied to members only

Winding details

Planning for IARU contest – Paul, G1GSN

As last year, Paul is hosting a ‘mini’ contest for members who want experience in contest operating outside the usual high profile and high pressure atmosphere. The venue will be the same as last year. Paul detailed the aerials which he will erect and the equipment to be used.

The contest is a 24 hour test, running from 13:00 BST start on Saturday, 13 July to the end at 12:59 BST on Sunday 14 July, with the exception of our shut down over night, I.E. 10PM to 9AM.

So, here’s a good chance for members to get some practice in contest operating in a relaxed atmosphere.

20 June 2019 – A Planned approach to Dxing – by Ken G4YRF

The presentation started with a look at sites giving up to date details of planned DXpeditions so you know when the operations should be starting. Then sites used to find real time information of the stations operating. That was followed by sites to let you know who in the world is actually working the DX and if there are G stations going through, if so, Work them yourself!

6 June 2019 – The micro car by David Wherrell

Messerschmitt KR200

David began by describing the parallel universe of cars. ‘Ordinary cars’ had four wheels, usually designed with the family in mind to travel in comfort. While the Micro cars were usually powered by cycle engines and had three wheels. Cost wise they represented minimalist motoring.  In fact, some early cycle cars were pedal powered!  One even invited passengers to join in on the pedals!

Numerous small car models were described like the three wheeled Morgan from 1909 followed by improvements in 1925 of the Morgan Aero and then in 1949, the F-Super. Dozens more cars like the Reliant, the Bond Minicar, 1953-1968, the Berkeley, manufactured in Biggleswade from 1956 to 1960 were described.  From 1953 to 1964 Messerschmitt made the famous KR200 three wheeler powered by a 200cc 2-stroke engine. A total of 30,286 were built!

In 1953 the Italian designed Isetta arrived on the market. Eventually, in 1955 BMW acquired the license to build them.. This popular model bosted a 300cc 4-stroke engine. Originally a four wheeler, it was changed to three wheels to benefit from lower road tax in Great Britain. A British version was produced in Brighton from 1957 till 1964.

Numerous other small cars were discussed finally arriving at the present time when it was revealed micros were still being produced in France, including the Daimler Smart car. In India, the Tata Nano which was well designed but not manufactured to a high enough standard to become popular

David pointed out that there are many car clubs in the country where members can find like minded enthusiasts who hold rallies where members can meet other owners and perhaps buy spare parts or get technical help.

1950s- BMW ISETTA 300