Sunday, March 30, 2014

Swapping Over the Cobwebs

Last Friday evening in a bit of madness during a bout of boredom, I decided to dig out the dismantled G3TXQ cobweb from the attic and set it up outside in the garden. I’d wanted to re test it against the present G3TPW cobweb I'm using, just to go over the pros and cons and possibly replace the G3TPW. 

With the G3TXQ quickly set up on a piece of 6ft scaffold pole and after doing an approximate tune I couldn't believe my luck when wondering over the 21Mhz band that I managed to have a qso with a Russian station who gave me a 599 which made me think maybe it was time to swap the cobwebs over. 

Saturday morning I set to work and I did the full tuning with the MFJ 259 which took an age as the G3TXQ definitely has much finer tuning points, it dips very quickly and the freq range is literally a few hundred kilohertz, a noticeable difference to the much wider freq of the G3TPW. 

Because I was tuning/trimming the antenna with the MFJ 259 at only 6ft above the ground I had to take the risk of setting each of the elements to tune a little lower than the freq I wanted to operate on, the theory being that once raised the SWR would rise slightly from the tuning at ground level.

By Saturday evening I had adjusted all the tuning, secured the ties and finally waterproofed the junction box, I hadn't needed to do this before because this antenna had only been set up in my attic, So by Sunday morning the G3TXQ was ready for mounting

I grabbed the ladder, lowered the 40ft mast and removed the old G3TPW cobweb, I’d forgotten just how heavy the antenna is and it took a while to gently bring it down the ladder back to mother earth.

Placing the two antennas side by side it was interesting to see the physical difference. The G3TXQ is so much lighter; certainly the single wire and smaller aluminium central clamps make all the difference. 

The G3TPW has a much heavier clamp and is beginning to look very worn!

The G3TXQ is a much neater and lighter clamp, a definite improvement.

I also needed to do a few adjustments to the mast, add some more kevlar cord guides and do some general maintenance. Once that had been completed I grabbed the G3TXQ and hoisted it up the ladder and clamped it to the top of the mast, I have to admit it was so much easier than with the G3TPW and just looked a lot tidier! 

The final result and there was a definite improvement in performance.

By the afternoon it was all finished and after a quick SWR check I called a CQ and got another Russian Station (Alex R3ZK in Belgorod) who gave me a another 599, I was very pleased with the final results. 

There’s a few little bits I need to do, (like add the top mast clamp cover which I forgot.....doh!) But everything went pretty well according to plan and I shall now dismantled the G3TPW and store it away in the attic until I have another mad moment!

Final SWR results for the G3TXQ:

20 meters   1:2:1
17 meters   1:1
15 meters   1:1
12 meters   1:1
10 meters   1:1