The Spiderbeam is a triband yagi made from fiberglass and wire and Sands ARCG have the three band version of the beam that once built will cover 20m 15m and 10m. The black cricket style bag holds twenty 4ft poles and the whole antenna weights in at an unbelievable 6kg or (12lbs). Here we are attempting to add a little excitement and wonderment to the afternoon and what do the members of the public do? turn their chairs around and totally ignore us...... I blame it on the shorts!
Our plans for today were simple, re-measure both the Kevlar and nylon lines. These lines are used to add rigidity to the poles and the correct measurement is crucial to putting the antenna up quickly and allowing for a unified tension across the Spiderbeam, in readiness for the wire antenna to be added. Our first task was to mount the center plate on the mast section we had brought with us.
Contrary to to what you might think looking at these pictures both Chris and I are working and have just finished a little teamwork putting the 4ft sections together. The final sections will be fitted just before the tensioning lines go on. Chris and Ian are just starting to lay the nylon tensioning lines out ready for measuring and adjusting the lines to the correct length.
You may be wondering where I come into this build again?...... Yes, Ian & Chris were wondering that too! Before we could do anything we all engaged in a spot of defankling..... Yep! we were so disgruntled putting the kit away on at a cold a blustery Sunday afternoon after accessing the damage to our beloved Spiderbeam caused by the "Great Storm" of 2009, that all the lines were just thrown into the bag.
Well you missed it..... I helped out with measuring all the lines to the correct length with Ian. Chris and Ian can now start attaching the lines to the Spiderbeam to give it the essential strength and rigidity.
One end of both Kevlar and Nylon line is placed over the center of the mast and the other goes just behind an O ring to stop it slipping.
All our planning and preparation was going really well, but disaster was about strike. You may remember from our last posting that the only way you could get some of the older poles to fit was to sand the collars down a little.
The effect of this was to prove devastating. As tension was applied to one of the fiberglass sets, there was a sickening crunch to be heard as one of the sanded sections broke. The factory set diameter is 35mm and this had been reduced by our sanding action coupled with possible micro fractures caused when the antenna came toppling down during the "Great Storm".
There is a bright side to all this doom and gloom...... despite the old darlings turning their backs to us at the beginning of the build.... A cook from Heysham's Curiosity Cafe
was sent over to find out what we were building, a lady walking her dog couldn't resist asking and a car with four young men in did a double take as they went up one of the side roads and came back for a closer look for 20 minutes or so.
The fault was found before we put the antenna up for the next contest in a few weeks time..... I know the whole group would have been devastated had this happened on contest weekend.
None of the effort and work put into this project has been wasted.
Replacement sections will not cost the earth and we should have everything ready to go for IOTA if not before.
Thanks to all who have put their time in so far: Ian G0VGS Frank G8BME and Chris G4LDS and of course Barrie G1JYB and his farmer, without whom we would have learned about the antenna's problems at a time we could least afford to.