C5DX - 2018 British School Kids to Gambia!
Sandringham School Amateur Radio Club DXpedition
ANNOUNCEMENT (as posted by G4DJX on QRZ.com):
C5DX licence has been granted and will be activated again between 9th February - 16th February 2018 as part of a school trip to the Gambia.
We are taking 18 students (sixth form) and 3 staff including myself to retrun to Farafenni Senior Secondary High School. This is our 10th year in collaboration and visiting the school. On this occasion we hope to see the next major project near completion - a major extension to their school library to create a dedicated learning space for students to use in and out of school hours. This has been achieved from fund raising at Sandringham School, St. Albans.
I will operate CW and four licenced students from Sandringham School Amateur Radio Club (M0SCY) who are also on the trip will operate SSB - Jessica (M6LPJ), Polly (M6POG), Morgan (M6MXD) and Stan (M6SQO). It will be their first DXpedition and they will be learning how to operate from a semi-rare country so please bear this in mind and be patient with them as they learn the craft of DX operating. Remember the DX code of conduct.
We will be running 400W using a K3, KPA500 and KAT500 into a multi-band dipole
(the new Aerial-51 Model 807 ultra-light OCF Dipole)
kindly donated by Aerial-51. SpiderBeam have also part sponsored this DXpedition with a 12m SpiderPole and associated equipment.
A VERY BIG THANK YOU to both Aerial-51 and SpiderBeam for this generosity.
SSB will most likely be on HF, whilst I will operate HF and also experiment with some LF bands depending on conditions and antennas. We will operate split - +1 for CW and +5 for SSB. Watch out for the spots and we look forward to working you all soon.
We will endeavour to upload logs to LoTW whilst there and possibly ClubLog. Pictures may be loaded here with updates if we get time to refresh - so call back to see what is happening.
LOOK FORWARD TO WORKING YOU ALL.
Alan Gray, G4DJX
Where there's a will, there's a way . . .
On their 2016 DX-pedition to Gambia, Alan took an Aerial-51 Model 404-UL along as his main antenna. For their 2018 expedition, they also want to operate 80m, run 500 Watts and preferably not need an antenna matchbox. The only mast would be a 12m Spiderpole.
Alan wrote to Spiderbeam and asked for help.
We had already developed two new versions of an 80m OCFD, one for 500w (807-L) and another for just 200w (807-UL). The 807-UL was light enough for the job but didn't handle enough power. With 600g (21 oz.) without coax, the 807-L was too heavy for the 12m Spiderpole.
Necessity is the mother of invention; I set about to trim excess weight off of the 807-L.
The first thing to go was the Epoxy-Potted Enclosure. This cut the weight by 30%. By also throwing out the SO-239 coax jack as well as the PL-259 coax plug, I saved another 36 grams.
To be sure they did not try to use too heavy of coax for the 12m Spiderpole, I connected 10 meters (33 ft.) of RG-313 directly to the balun; I wound the 1:1 Guanella balun onto one end of the coax and then soldered it directly to the 4:1 Ruthroff balun. The remaining coax was just long enough to run down the full length of the pole .
The result was the antenna pictured above. It fully meets the requested requirements!
The 12m Spiderpole will be shortened to just 10m height, giving it the strength at the top to support the 807-UL "Special". The pole will mount on a balcony on the top floor of the hotel, placing the feedpoint at about 20m (66 ft.) height - plenty for 80m.
The 'RMU' in the picture was necessary to raise the frequency of minimum SWR into the SSB portion of the 80m band. If they had been willing to use a matchbox, that would not have been necessary. We would have just made the long leg 25cm (10") longer.
Shortening the overall length of the antenna is a NO-NO.
This would throw out resonance on the higher harmonic bands.
WE WISH ALAN AND THE KIDS THE BEST OF LUCK!
The Aerial-51 Team
Rick, DJ0IP & Sebi, DO5PNS