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.
Over the weekend of 31 March to 2 April 2017, a small group of us installed a KiwiSDR into the equipment rack at GB0SNB, alongside GB7KH repeater. The KiwiSDR (pictured below) is a cape for a BeagleBone single board computer, similar to the Raspberry Pi. It was kindly provided by David G7UVW, who also helped with the install. A direct link to the WebSDR at GB0SNB is found here: http://sdr.gb0snb.com/.
A new run of high quality CTF165 connects the receiver hardware inside the Shack to the WellBrook Loop antenna mounted on the mast.
This is the first stage in the installation, and the next step is to reduce the electrical noise present at the receiver; unfortunately, this may not be quite so easy in a bunker the size of this!
The receiver is available for public use, and may be found on SDR.hu. A direct link to the WebSDR at GB0SNB is found here: http://sdr.gb0snb.com/.
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.
The RSGB 50/70/144/432MHz Christmas Cumulatives Contest series run from the 26th to the 29th of December each year and are intended as a bit of fun in the contester’s calendar. The contest exchange is the usual RS(T), Serial Number and 6 character locator (e.g. JO01DQ). These contests are really easy to become involved in, and often provide a good excuse to escape the house after Christmas.
This year, Dave M0TAZ, Dave M0YOL and George M1GEO decided to operate alfresco from the Bunker for the final two days (George having put in token entries on the 26th and 27th for 144 MHz from Home). We operated on 50 MHz, 70 MHz and 144 MHz for the full 2 hours on a picnic table, in large overcoats on cold winter afternoons, packing up in the dark!
144 MHz was to be our main band. For that we used an Icom IC7100 transceiver, DG-8 masthead-preamplifier (GM3SEK design/M1GEO construction), and 9-element tonna (10m AGL), powered from a large 60 Ah sealed lead acid battery.
50 MHz and 70 MHz were run as a sub station. Again, using an Icom IC7100 transceiver and an InnovAntennas 6-element dual band (50/70MHz) yagi (7m AGL), with an 85 Ah leisure battery. The battery also provided mains power via a small inverter, which charged the logging laptops.
The table below shows the number of QSOs made per band on each day, as well as the best DX station callsign, locator and distance. In order of fairness, we switched callsigns on the second day, all points awarded to the SNBCG.
Members of the newly formed Secret Nuclear Bunker Contest Group (SNBCG), M0SNB, met for its inaugural Christmas Meal on Saturday 12 December 2015. The event was well attended by 10 members, with some sending their apologies for absence! The group enjoyed a traditional Christmas Dinner, complete with crackers and hats, as well as the unavoidable cracker jokes! The event was expertly organised by Pete, G0IAP.
Members started to arrive early, and began chatting and discussing the new year’s events. There was much to celebrate, given the SNBCG is now affiliated to the RSGB with the callsign M0SNB as well as the long-standing GB0SNB permanent special event callsign.
Last night saw activation for the 160 metre club calls affiliated societies contest. This is a slow and relaxed contest, with an emphasis on beginners (full rules here).
3 members of the group decided to run the contest from the bunker as there is already an antenna suitable for 1.8 MHz on site. We carefully negotiated the car on to the field (in heavy rain), with the wheels slipping everywhere. As some of you may remember, we have had vehicles stuck in the field before, so it was our concern at 8pm at night with the farmer long since resting at home, that we mustn’t become stuck!
The field was boggy, but we managed to get close enough to run a coax to the mast, and set the station up on the car dashboard. Given we didn’t know the state of the antenna, we took a large ATU with enough inductance should it be needed, with the intention of running a long wire if the doublet had failed. The Icom IC7100 was used to provide the maximum 32W for the section of 160m in concern. Power was provided by a Honda EU20i silent generator. We also opted for a small fan-heater to keep the car warm and small table-lamp to provide light. Fortunately the doublet was okay, and we got underway.
Here we see Dave G7UVW operating the IC7100 through a rain-covered window.
Conditions were very down on last year’s event. The band was cursed with environmental noise. It also didn’t help that we had a dodgy piece of feeder coax, which was undiscovered until the last 15 minutes.
Overall, we worked 34 stations, and claimed a score of 564.
This weekend saw members of the bunker group activating the site for the CQWW SSB Contest. Operating from the Dave M0YOL’s caravan awning, we set up two stations, one at each end.
We arrived about midday on Friday 23rd October and got setup. Dave M0TAZ was underway with the construction of his 21 MHz beam while George M1GEO and Dave M0YOL were setting up the caravan. Some time later the 14 MHz beam was built and put on the SCAM12.
Then food! Here, we see the pre-contest dinner inside the awning, with (left to right) Dave M0YOL, Dave M0TAZ and Chris G8OCV.
… and breakfast …
Icom IC7700 HF transceiver
Heathkit SB200 amplifier
Yaesu GX600RC rotator
Kenwood TS990 HF transceiver
HAL 1200 amplifier
14 MHz 3 element homebrew yagi
21 MHz 4 element homebrew yagi
1.8/3.5 MHz doublet; 26 metres
28 MHz vertical dipole; 8 metres
7 MHz ground-plane vertical; ground level
The shack was powered by two Honda EU20i 2kW slient generators with phasing harness, delivering a solid 4kW of mains power. We were a bit worried with the heavy rain on Saturday, so we fashioned an umbrella to help protect the electrics!
During the evenings, it got pretty cold. Here, George M1GEO operates with hood up for insulation, while Dave M0TAZ’s amplifier reports 8C inside the shack.
Band conditions were good (and busy), and many QSOs were made over the weekend. At the start of the contest, some of the lower bands became very packed!
Overall, we worked 1434 in our casual operating weekend. You can see the full log here. Some interesting contacts include Tunisia, many Caribbean Islands, China, Ceuta & Melilla, French Guiana, Liechtenstein, African Italy, Japan, Australia and New Zealand. For more information, look at the full countries breakdown!
A more comprehensive breakdown of QSOs per band can be found here.
Much more analysis and breakdown can be found on the CQWW 2015 SNBCG pages. Analysis by SH5 v.2.39, Dmitriy Gulyaev UA4WLI.
A big thanks to Dave, Dave and Dave (M0YOL, M0TAZ and G7UVW) as well as Chris G8OCV, Pete G0IAP and George M1GEO for making the weekend possible.
This weekend a few of us decided to head down in to the Shack at GB0SNB to do some operating. The HF bands were full of stations in the Worked All Germany and BARTG RTTY contest, as well as JOTA activation stations.
In between working a few on HF, we managed to pull around 20 contacts on 2 metres, and had a nice pileup on 145.400 MHz.