Category Archives: Event

Easter Field Weekend

During the long Easter weekend members of the SNBCG came together for a radio weekend. Over the course of the four days, two HF stations were set up; one on 7 MHz and the other roaming between 1.8 and 28 MHz depending on propagation.

Dave M0TAZ decided he would try a 1/4 wave vertical on 7 MHz and use his recently purchased push-together fibreglass poles. These poles are often sold at radio rallies in packs of 5 (each pole 1.3 metres) to give an overall height of 6.5 meters. Using two packs of the poles, the required height of 10 metres was achieved.

Chris G8OCV had made some supporting guy rings, these provided anchor points for the guy lines at approximately 4 and 8 meters. The first attempt didn’t quite go to plan, it simply wasn’t possible to walk up the 10m pole, as we found out when we exceed the bend radius of one of the poles. Lesson learned it didn’t make any difference as the fracture was in the joining section that was simply moved to the first section. In the end, we used 9 poles, giving us a total height of 11 meters with a simple wire running down the side for the radiator.

Six 6 radials were cut, each around 10 meters in length, and the antenna was mounted at the base of a wire fence. The earthing system included the 6 radials and the wire fence, and this provided a reasonable match around 1.5:1 at 7.150 MHz. It would have been much easier to use a push-up fishing/roach style pole but experience has taught Dave that these can be tricky to keep up without guying and tapeing over the joints. As we wanted to run linear amplifiers this weekend, the prospect of the pole moving in the wind and/or falling down made, we made up our minds to use push together poles as the first choice. The antenna was fed with coax with a choke unun (or balun) at its base to stop the coax radiating, and this needed to be capable of high power.

The antenna provided reliable service all weekend, and with the addition of 400W yielded over 200 contacts in 40 DXCC countries. An enjoyable part of the weekend was working DX stations later in the evenings, including the USA, Chile, Mozambique, Guinea-Bissau, Israel, UAE, Armenia and Asiatic Russia all on the 40 metre vertical.

DXCC Breakdown on 40 metre vertical

George M1GEO, Fred G3SVK and others operated the other station. George chased some good DX and Fred worked several hundred stations as “GB0SNB” in CW.

Below we see the DXCC breakdown of the second station using the mast doublet on 160 and 80 metres, and the beam (pictured above) on the higher bands. Some of the DX on the doublet and beam included several QSOs into Japan, Fiji, Trinidad, Guinea-Bissau, Cayman Islands and Argentina.

DXCC Breakdown on 160m doublet and HF beam

We also had time for a BBQ and some excellent curries provided by Fred G3SVK. It was nice to see Camb Hams members Geoff G0DDX and Linda G0TPX, and LEFARS members Derek M0XDC, Dave M0MBD and Dave M0VID. RSGB regional man Peter G0DZB also joined us for the afternoon, making the most of the good weather for a ride on his motorbike, and Bill G0IQK popped in on the Sunday afternoon.

Dave M0YOL worked some data modes using his portable setup. All in all, a good weekend was had by all.

The first 50 MHz contest of the year

Members of the SNBCG took part in the first 50 MHz contest of the year at the Kelvedon Hatch club call M0SNB. The contest ran from for 3 hrs on Sunday morning (10 till 1) the weather was forecast to be 23C and sunny. We opted to operate outdoors using a 5e beam on a 10m pump up mast. The radio was an Icom 7600 and Expert 1.3 K-FA provided 400w power was provided by a Honda EU20 generator.

The band seemed very busy, with lots of stations taking part, and I think the good weather helped encourage more portable operating. Over the course of the next 3 hrs we worked 63 Q with our best DX into EI at 585 KM. Conditions seemed average, but we did have some very rapid QSO on some of the longer paths, sounded very much like aircraft flutter.

A very enjoyable contest in the sun, thanks to everyone we worked.

You can find the claimed scores online.

You can view the RSGB VHF contest calendar online

You can read more about the Kelvedon Hatch Secret Nuclear Bunker and the SNBCG here.

SSB AFS Contest

With snow on the ground and the sun in the sky it must be time to do some winter contesting. This weekend members took part in the RSGB affiliated society SSB contest, this takes part on 7 and 3.5 MHz from 2 till 6 PM.

With a small amount of snow on the ground, and ambient temperatures around +1C we opted for the inside operating position. The station comprised of an Icom 7600, Expert 1.3KFA solid state linear and a doublet antenna at 30m on the bunker tower.

Band conditions on 7 MHz only supported “long skip” with some good signals from Scotland and Ireland, although after a short while even these distances proved difficult. The maximum usable frequency had moved down to 4 MHz, and so a switch to 3.5 MHz was required.

A look on the Hack Green SDR confirmed 3.5 MHz was very busy, and we soon realised it was hard to find a run frequency. We also noticed a large amount of rasping electrical noise on 3.5 MHz, and so decided to investigate further. At times the signal meter was reading S9 or s9+10dB and so hearing weaker signals was proving impossible.

We changed the mains supply over from fixed to generator, and the noise floor dropped by 3 to 5 S points, interestingly it would seem the noise was coming from the mains, and so this would require some further investigation and most likely a mains filter project for Chris G8OCV.

The generator proved to be a little problematic, for some reason it was running a little lean, and so the engine was sounding rather more stressed than usual. This caused the generator to “brown out” a few times as it coughed, wheezed and spluttered in its attempt to generate circa 2KW at 240v. As they often say if something could go wrong, then it most probably would while your out in the field.

Hopefully the generator will be a simple fix, probably just needing a clean to the carburetor and no doubt another job to be added to the “to do list” before our next event.

While we had some fun, drank some tea and generally worked a few people I think its safe to say our score wont be breaking any records. As always we learnt a bit, had fun and generally tried to stay warm.

RSGB Christmas Cumulative Contest

The RSGB have a series of Christmas Cumulative contests covering 50/70/144 and 433 MHz. The contest is a chance to put down that turkey sandwich and head out to play some radio in the winter sun. The contest run for 2 hrs, and activity is over 4 days. You can read the rules online, and activity is typically quite high.

This year I joined George M1GEO at our contest site the Secret Nuclear Bunker

The setup included.

Icom 7100, 9e Portable Tona and RF power was provided by a Linear Amp 300w solid state amplifier. The mast was a Racal PU 12 at 5m as the band was wide open with tropo propagation, this provided some interested DX. Mains power was provided by a silent running 2KW Honda generator.

We managed to work 51 stations, with our best DX into Spain, EA1FDI in IN53 at 1143 KM.

The QSO map showed some great openings to the South and East.

The temperature dropped quickly once the sun set, providing a spectacular sunset and the motivation to pack away quickly. Altogether a great afternoon playing radio, with some great propagation for a change.

Thanks to everyone we worked, and all the best in 2017.

EME and MS Weekend

Members of the Secret Nuclear Bunker Contest Group (SNBCG) assembled at Kelvendon Hatch to try 144 MHz (Earth Moon Earth) EME and MS (Meteor Scatter) over the weekend of the ARRL EME event As a group we have tried with some success MS QSO and this helped lay the foundation for this weekend’s EME event.

EME is particularly challenging due to the great distances involved and extreme path loss of the signal after its travelled close on 500,000 miles! The equipment and format of the QSO is similar to MS, we used the WSJT-X 1.7 (currently in Alpha) and WSJT provided free from Joe Taylor K1JT website.

The weekend of the ARRL EME event was selected as it provided the best chance of working some of the EME “big guns”. Our equipment was quite modest by comparison, but included a

9 Element LFA antenna designed by Justin G0KSC,

DG8 masthead preamp as designed by Ian GM3SEK with the kit available to order from hupRF.

Linear amp UK Gemini 2 VHF amplifier delivering 300w.

Low loss LBC600 / LMR600 coax.

Icom 9100.

We found we could often decode signals, and even the thrill of decoding signals from the K2VEE in EM79 via the moon was incredible…then it happened.

We answered a CQ call by HB9Q and to our surprise they replied. This was our first and it turned out only EME QSO that weekend.

We continued to have quite a few MS QSO working Italy, Slovenia, Denmark and Norway and also a number of SSB contacts with 30 or so UK stations over the course of the weekend.

It is always nice to try a new mode and to succeed, you must never underestimate how difficult it is to achieve a QSO over that incredible distance. We achieved our goal of making an EME QSO, and regular decoding of signals via the moon. If this has inspired you to have a go I would encourage you to check out K4MSG guide to small station EME. Also have a look at W5UN monster EME array that has bagged him over 11,000 EME QSO !

QST also published an interesting article “A Basic Approach to Moonbounce” that you may find interesting.

Plans are already being made for the next EME event in November…

RSGB IOTA contest

Members of the SNB Contest Group came together to play some radio in the RSGB IOTA Contest. Some stations make the trek to far flung Islands in exotic parts of the world, we opted for the contest site close to Kelvedon Hatch in Essex.

The SNB contest site has the added bonus of a 50m onsite mast, making an ideal platform to hang dipoles. George M1GEO and myself decided to operate or respective calls from the two radio setup, using 3.5, 14, 21 and 28 MHz. George also added his 50/70 MHz beam on the mast, and this provided some interesting contacts using MS and JT65.

With the able assistance of Dave G7UVW, Chris G8OCV, Peter G0IAP we soon had the antenna ready.

Two pump up masts provided the following setup.

Clark 12m: Tri-band Beam A-3S covering 14, 21 and 28 MHz, with a 50/70 MHz beam.

Clark 10m : 15m 4e homebrew monobander.

Bunker: 3.5 MHz dipole at 30m centre

At various times we added some RF power from either the solid state Expert 1.3KFA or the HAL1200_Atlantic amplifier. We had some interaction between the close sited antennas, and at times this dictated the operating modes/times.

Fred G3SVK provided joined us as our CW operator, Fred can often be found in the lower pasts of the bands chasing big DX.

No sign of the great man this weekend, but, we live in hope.

70 MHz Trophy Contest and CW QRP HF

George M1GEO and Dave M0TAZ took part in the RSGB 70 MHz trophy contest this weekend at the Kelvedon hatch Secret Nuclear Bunker contest site. The weather was ideal for alfresco operating, using the Icom IC-7100 and homebrew 6e beam at 10m on the Racal PU12 mast. Using 50W and a 85Ah leisure battery we operated from 11am till 4 am.

Here you can see the PU12 and home-brew 6e 70 MHz beam. Operating from the base of the mast provided quick access to turn the beam. We managed to work 59 QSO with best DX into Scotland at 518 KM. The QSO map is shown here.

Meanwhile Rob M0VFC was operating QRP HF on 3.5, 7 and 14 MHz using a range of dipoles. Unfortunately the HF bands have been a challenge at the best of times during the day, and QRP provided to be interesting. After a few hrs operating Rob had completed 30 QSO, and under the conditions that counts as a sterling effort! Here you can see Rob operating from the boot of his car. No appearance from the great man.

Altogether another great weekend of alfresco operating in the sunshine.

50 MHz Trophy Cup & International Museums Weekend

The weekend of the 18th and 19th of June saw members of the group assemble to operate as M0SNB for the 50 MHz Trophy Cup and GB0SNB for the International Museums Weekend.

Over the course of 24 hours for the 50 MHz Trophy, we made a total of 218 QSOs, with our best DX to UZ5U (2320 km). The map shows our contacts.

Maps and logs from the Museums weekend will be added once the logs arrive from the IWM station manager.

Upminster Windmill on the air

National Mills on the air weekend is a chance to combine amateur radio with the national windmills open day. Although not directly related to the bunker, the SNBCG decided to activate Upminster windmill as it is our local mill – it was a delight to operate on the green opposite the mill once again! The mill has stood on the green in various guises since 1803, and recently thanks to the National Lottery Heritage Fund its just secured large grant to complete some restoration and the building of a education and visitors centre.

Unfortunately due to the ongoing building work members of the public were not able to visit the mill this year, but that didn’t stop them coming to visit us operating radio in the field.

(Back Left Dave M0YOL, From Left John 9H5G, Peter G0IAP, Chris G8OCV and George M1GEO)

This years event was well attending, with our furthest operator travelling from Malta to guest operate. John 9H5G operating (left station) retired to Malta, but often travels back to the UK. We were delighted to welcome him to the team, and he was soon pressed into service on 7 MHz managing the pile-up.

We operated using 2 x Icom 7100, making use of 5, 7, and 14 MHz on HF and 70 and 144 MHz on VHF. Over the course of the weekend we contacted over 30 mills and 150 others stations from all over Europe.

Thanks to everyone we worked, QSL is via eqsl.cc 73

CQWW WPX SSB Contest 2016

Over the 2016 Easter public holiday weekend, the team at the SNBCG decided to participate in the CQWW WPX SSB contest, using the club callsign MX0SNB. On arrival, our usual camp location close to the bunker’s communication mast had become unusable due to recent wet weather, with the grass boggy to say the least! It soon became apparent one of the vehicles was stuck in the mud, and after much pushing and pulling we decided another location would be required. Luckily the owner of the site offered us another location, higher up on the hill with the added advantage “that once onto the hill your vehicle only need to slide down to the bottom of the hill to exit” – a very useful feature!

Using George M1GEO‘s 14 MHz homebrew beam and Dave M0TAZ‘s 21 MHz beam, we set up our stations on a lovely sunny Friday afternoon.

Power was provided by 2 x Honda EU20 generators coupled together and providing 4 kW of peak-power. Enough to run the two stations with amplifiers and a kettle for making tea!

Dave M0YOL kindly offered his awning, along with copious cups of tea, bacon sandwiches and supplies throughout the event. We had completed the set up before sun down on Friday, allowing us to complete some testing with both of the solid state amplifiers.George M1GEO and Chris G8OCV had recently purchased an SPE Expert 1.3K-FA amplifier and Dave M0TAZ was using the hal1200_atlantic, with both amplifiers are capable of providing over 1kW of RF power, more than enough to meet the UK full legal power of 400W.

George M1GEO and Chris G8OCV have designed and built a 3 element 14 MHz beam, the design uses roach poles and provides a lightweight portable beam. The 21 MHz beam Dave M0TAZ constructed was based on DK7ZB design, and the construction details have been previously discussed in this article on his personal website.

The set up inside the caravan (trailer) awning provided a dry and largely windproof operating position, although at this early in the year the evenings are somewhat chilly! The weather provided a real challenge as the weekend progressed. In such a high and exposed location, with storm ‘Katie’ approaching the south of the UK.

Over the course of the next 48 hours, the rain and the wind increased to storm force with gusts in London of 50 mph, and in our exposed hilltop location gusts in excess of 70 mph were felt rocking the caravan.

This video, comprised to clips from throughout the weekend captures the more sane parts of the experience, with the scary parts unrecorded (because we were all too busy holding things down)!

We lowered the beams and continued as best as possible using a vertical and doublet antenna – well, it started vertical!

Late on Sunday night and in early hours of Monday morning, the storm really hit had, the awning was in danger of parting from the caravan so the decision was taken to quickly move all the equipment into the safety of the caravan. It wasn’t until the following morning, when the storm had passed, that we were able to assess the damage!

Unfortunately the beam is not likely to make any further field days, but George M1GEO and Chris G8OCV do have plans for a mark 2 aluminium version soon.

Dave M0TAZ‘s 21 MHz beam fared a little better with the weather and survived the storm, but unfortunately, the mast will require a new guide rail (a plastic wedge that stops the mast rotating) due to the wind loading put upon the mast in the storm.

Despite the awful weather conditions we did manage to work 744 QSO in 94 DXCC in the main on 14 and 21 MHz.

The following maps show QSO made on 21 MHz (Red pins) and 14 MHz (Yellow pins) showing North America, South America and Asia.

You can view the log and further statistics online using the excellent SH5 contest log analyser software.

GB0SNB/MX0SNB/M0SNB – Kelvedon Hatch Secret Nuclear Bunker

RSGB affiliated amateur radio contest group & special event station in a RGHQ 5.1 Cold War Nuclear Bunker, hidden in the depths of Essex!