George M1GEO and myself 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 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 PM.
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 Altogether another great weekend of alfresco operating in the sunshine.
The 50/70 MHz interlaced beam is interesting as it uses a single feed line, and respectable gain for a 2m boom length.
Racal 12m PU12 mast. Push up 12m mast
Mast head preamp 11 to 18 dB gain.
Power was provided by 110 Ah leisure battery
Radio Icom 7100 at 50w.
Masthead amplifier for 144 MHz provided by George M1GEO. The design was originally published in the RSGB magazine RADCOM plus issue 1 designed by Ian White GM3SEK. The details are published on his website, detailed as the DG8 low cost, high performance preamp for 144 MHzConditions seemed good to the North, allowing us to work some good DX. On 144 MHz our best DX included GM4JR in IO85 (368 km) , MI0SMK in IO64 (524 km) and GD8EXI in IO74 (429 km)
Maps showing the QSO enclosed.
Thanks to everyone we worked, from a rather chilly Kelvedon Hatch.
Exposed on the side of a 50 meter mast the antenna often requires maintenance. George M1GEO and Chris G8OCV have over the years perfected the best way to mount the antenna, and on this occasion is had lasted close on 2 years. Antenna maintenance in the afternoon sun is much preferable to winter rain, so we too advantage of the weather to pull up the new doublet antenna.
The doublet is 40m per leg, into 300 Ohm ladder line and then a 4:1 Balun.
The centre of the antenna is made from a plastic chopping board from one of the discount value stores, ideal for insulators. The wire is multi strand 13A flex, ideal for antennas and hopefully robust enough to survive the winter weather.
The centre of the antenna is pulled up onto the mast, elevated to 20m and the ends are on one side into a tree and the other a warning siren.
Dave M0TAZ (Left) and Chris G8OCV working 80m SSB
Its quite difficult to locate suitable points for the antenna ends, and elevation without snagging in the local trees is always a challenge. Once setup we managed a couple of QSO on 80m.