Thursday, October 25, 2012

Getting ready for CQWW phone

Once again we are at the end of October, synonymous for many hams around the globe with CQWW SSB, a festival of contacts on the air for 48 hours.

For the fifth year running, I will be taking part in the multi-single team at ED5T with my friends Victor EA5KV, Elías EB5KT, Jose EA5GS, and Juan Carlos EA5UF.

In order for all of this to happen, there has been a lot of preparatory work going on behind the scenes, and apart from the above mentioned, we have counted on the multiple skills of Juan EA5GIE and the helping hands of Belar EA5YI.

This year, we decided to concentrate our pre-contest efforts on an area where we could do with making some improvement and which, if successful, will give a boost to our score. I'm talking about antenna improvements on 80 metres.

Our mainstay antenna at ED5T for many years has been a bazooka, held up in an inverted V from tower 1. In last years CQWW, the antenna failed on us in the middle of the night and was replaced by a half wave dipole which appears to work just as well. In the past, and in an effort to try to improve over the bazooka, we tried a single full size vertical, a two element full size vertical, and a vertically polarized delta loop. None of those antennas worked better than the bazooka.

Based on that experience, we decided to build a rotatable dipole, on the basis that a) the ends would be higher off the ground and in theory perform better and b) we would be able to rotate it to be broadside to wherever we want it.

The design chosen was a helical winding on fibreglass and aluminium tips for tuning. The antenna is 24 metres long. Part of the reason for choosing this design was that we already had a lot of the material available. The drawback is that since it is physically smaller than a full size, it will not be as efficient, and also will have limited bandwith. Also, the use of fibreglass makes proper guying obligatory due to it being extremely flexible.

The antenna was assembled and tested on the ground and looked good. However installing the antenna was not easy and when finally up, the resonance had risen 200KHz. It took another day and a lot of hands to get it to a more reasonable point and to get it back up in the air. In this photo you can see Juan and Victor finalising assembly.

As you can see, it was already dark by the time we finished. Again....

How does it work? Ahhhh, can't tell you that! You'll have to wait until after the contest to find out! :)

Tomorrow, setup of all the gear, including beverages in the forest courtesy of "Magic" Andreu, EC5AA. And at 0000 utc saturday..... CQ CONTEST!

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