Monday, May 18, 2009

Antenna Activities

Over the weekend an RSGB 144MHz contest was on. I thought that this would be an excellent time to find out how my newly constructed Moxon Rectangle performed. For a few hours after the start of the contest I heard nothing at all. But eventually I did hear some fairly weak signals, enough to show that the Moxon has noticeable directivity and a good front to back ratio, exactly as it should have. Unfortunately it also illustrated that VHF under normal conditions offers only line of sight propagation and if there is a mountain range between you and all the other band activity you won't hear anything.

On Sunday, a blizzard of red lines on the 50MHz real-time map spurred me to go up in the attic and add a 6 metre dipole to my four band attic dipole. This was a nice easy job - I only had to prune an inch from the end of each length of wire to get the resonant point where I wanted it, and I observed no effect whatever to the 80, 40, 20 and 10m dipoles sharing the same balun and feeder. I haven't worked anyone on 6m yet but I heard a beacon in Croatia coming in nice and strong, so it's just a case of waiting for the Sporadic-E clouds to be in the right position. I used to have a delta loop for 6m and made Sporadic-E contacts in the past using my K2 and a Ten-Tec transverter with just 7W output, so I'm hoping the K3 with 100W will do even better.

While I was in the attic I decided to get the Moxon Rectangle out of the shack and up there as well. I used the length of RG-58/U left when I took down the 2m Slim Jim, and since I didn't have any way of fixing it I just rested it pointing south east on an old plastic beer crate normally used as a support for cutting wood and similar tasks in the garden. My wife wants the beer crate back so I have ordered a cheap antenna rotator on eBay which will allow me to turn this little beam from inside the shack. I hope this will not prove to be a waste of money. The 2m contest showed that I cannot expect to hear anything during normal conditions on Two so I'm hoping that tropo and Sporadic-E will still be capable of bringing signals over the mountains and allow me to make some interesting VHF contacts in the coming months.
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