2015-10-05

Antenna testing.

Today was the first time I tried out my RigExpert antenna analyzer. What a neat instrument.

I am in the process of tuning a multiband dipole for the HF bands. Still not finished, but using the analyzer to see the SWR curve (or Smith chart, or R and X) makes antenna construction so much easier.

The process is not yet finished, but I have, at least seen that I can operate in the full CW bands of 15 and 20m without an antenna tuner, and about 50 kHz of the 80m band as well. The rest is still to be adjusted. When the adjustment is complete I expect to be able to operate on the full 15m and a good part of the 20m band without using a tuner.

The antenna is a bit low in resonance frequency, probably because of the low height of the end points. I think that it will become possible to operate most of the 40m CW band without tuner. The rest of the old bands (80/40/20/15/10) will need the assistance of a simple tuner.

On the other hand, my 10m half wave vertical provided a rather interesting result. Two minimum SWR points on 27.7 and 28.6 MHz. I suspect that one is the real resonance frequency of the antenna, and the other appears due to some accidental matching provided by the cable length used. More test to follow on that. The end result is that the antenna is below SWR 1.5 from 26.9 to 29.7 MHz.

A very universally applicable antenna.

Later some more experiments are in order.

One thing I do want to test is making antennas less obtrusive. A shining half wave aluminium vertical is rather visible when seen on the background of trees, and when it stands on a surplus military mast (yes, green) it looks like it is floating in the air.

I am looking for a paint for metal antennas that will not deteriorate  the performance, at least very little. Any ideas. I will be looking up paint on the net in the next few days, but any input is appreciated.

For now I have a paint mix that should be tested with a simple 2m aluminium dipole, now that my test equipment is coming into operation, albeit slowly.

One more thing I have to look into, is guy wires that are less obtrusive than the white flag lines that are more generally available, along with having high strength and good insulation properties.


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