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cat 6 cable for radials on a vertical? Is it a daft idea?


#21

Thanks Walter, that was my thought as well that the “upper part” of the antenna is more critical.

Andrew - yes I know adding resonant radials would be an improvement, my question is about generic non-resonant radials as this is a multi-band vertical ( it has a slider on its loading coil under the 2.5m high whip ) - some more details here: https://komunicapower.com/en/inicio/707-komunica-portable-multi-band-antenna-7-3050mhz-adjustable-pl-259.html
Understood that this is all very ground-specific but if you feel there may be some increase in bandwidth if I add some more, I’ll make up an additional bunch of radials and give it a try. The radials are already raised as they come off my tripod (you can just see the yellow wires in the picture below):

This is at DL/AM-058 Hinteres Hoernele yesterday where it bagged two contacts into the US, two into the UK, one into sweden, one into Greece and two within Germany in just over 10 minutes with 20w SSB. Bandwidth (and hence tuning) is not bad on the tripod but on a car roof, it’s better hence the thought of increasing the 4 radials to eight.

73 Ed.


#22

Hi Ed,
There is every chance of improving the performance as you more closely approach the ideal ground plane. And I think the improvements seen from the very skeleton-like ground plane to double that number of radials will be measurable. I would like to know what you find if you put just two full size quarter wave radials on it. There is a world of experimentation out there with such antennas.

73 Andrew VK1DA/VK2UH


#23

Hi Andrew,

Just a point of clarification, improving the efficiency with better radials will improve the Q of the antenna and reduce it’s bandwidth, but of course the radiated power is increased. Low broad band SWR usually means low efficiency.

73
Ron
VK3AFW


#24

Actually my previous tests have shown that putting just one radial (counterpoise) which is trimmed to length using an analyser per band and then taping those 5 leads together and laying them out in one direction can give a working solution but this is more a counterpoise than a set of radials of course.

Not changing anything until after tomorrows transatlantic S2S event, but I’ll most like try doubling the number of non-resonant length radial in the nect week to 10 days and see what happens there. What Ron says is what I would suspecting may be the case - adding radials can narrow the bandwidth of the antenna (albeit with improved performance on the set frequency).

Ed.


#25

Hi Ed,

Working into the US on that little whip is impressive. Well done.

The whip is of course only half the antenna and with a bigger ground plane like a car the results as you say are better.

I would consider that the radial/ground plane arrangement is half the aerial and if all is well the fields from the currents in the radials cancel each other out and all the radiation comes from the whip. But if not properly done a lot of power can be consumed in the ground under the radials or in the case of a single radial lost both in the ground and straight up.

I know some people advocate using multi-conductor cable and cutting the wires to different lengths for multi-band radials but have never found this to work except on and only on the lowest frequency. My conclusion is that the wires are too close together to operate independently. Separate the radials.

YMMV.

73
Ron
VK3AFW


#26

Hi Ron, with my “set of counterpoises” of different resonant lengths I did tests with them separated or together on 40, 20 & 15m and found no difference. Now multiple raidials on each required band, tuned to length, do need to be separated from one another otherwise they act as a single counterpoise on their band.

I’ll be trying with the loaded whip again today, but will also have the dipole up, so that I can do some comparisons on 20m - I have more space at today’s summit. The dipole will also work better on 40m. The whip covers 40m but it’s getting more loading coil than whip at the low frequencies. I may give it a try on 40m - who knows, it might surprise me.

73 Ed.