Ham Radio

Friday, February 15, 2008
Antenna Maintenance
This time of the year here in the U.K certainly puts any outdoor antenna systems under a lot of strain from windy, wet, winter weather.

I decided to do some routine maintenance on my antennas. The first job was carried out on the reasonably recently erected delta loop cut for 20meters.

I took the loop down from the horizontal configuration, which also meant that the mast it was supported by which was also the fixing for my vhf vertical also had to come down.

This allowed access to both antennas, so I began with the loop by shortening the overall length of the loop, which involved cutting 500mm of each length. The shape being triangular meant removing a total of 1500mm (1.5 meters) of wire and then re measuring each side of the loop to ensure that it was still divided into 3 equal sides. Each side now measuring 6.2 meters in length, giving a total wire length of 18.6 meters.

Previously the swr had been at 5.0 on 14.200, the swr with the adjustment was now 2.0 a much more resonant length for this part of the band.
The antenna worked well before in the horizontal position however it did bring in a high noise level. So with this in mind and the adjustments of the length completed, I decided to erect it this time as vertically as the nearby tree that was to be used for support would allow me. I was fortunate to be able to configure the loop vertical, with a slight slope towards the bottom.

To my amazement once I switched the HF rig on (Yaesu FT-767 GX) the previous noise level was non existent and I was able to hear radio 5 audio with 0 signals coming through from DX stations. I commenced some tests and tuned the loop down to 1.0 swr reading using the auto antenna tuner (ATU) that was onboard the 767. The first station I worked was N2AO followed by WX3B, both were good signals in and out with the loop and when I switched to the vertical hustler the noise level was back and the signals were slightly down.

The loop was much better and it was also working very well on 17 meters as well. After a few days in test I am still getting much better results from the loop, however (and thankfully after spending money on the commercial hustler antenna) the vertical occasionally received bigger signal readings from some directions. The loop has definitely been the favourite for all round receive due to the nice sound of audio signals and the distinctive lack of noisy QRN that it doesn’t bring in. I am very happy with the home made loop antennas overall performance.

The small homebrew vhf vertical also got some attention when the mast was down, I cleaned the connections as well as the whip. I also checked over and repositioned the 3 ground plane radials that are fixed to the antenna's base. This had also surprised me once I began some tests, as local signals had become slightly stronger by a couple of S-points.

I made some contacts on 2meters and managed to get a 5/8 report from G1KDU who is approximately 200 miles south of my QTH. The Band has been in good shape with few good openings quite regularly recently, so a bit of maintenance on the antenna again paid off. I went on to 70cms and managed SSB contacts with a couple of reasonably distant located G-stations, that were operating during a contest. Once again I was quite pleased with the simple antenna's performance.

I guess it is quite advantageous to carry out regular maintenance on your antenna to help maintain good performance, especially where they are exposed to the elements like mine.

73 have a good weekend. de 2E0HTS
posted by Simon Davison @ 1:37 pm  
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