Radiation Resistance at Sunrise
Sunrise finds me once more on the road, running with my 3" 10-80 meter gearmotor antenna with its very efficient combination whip/caphat.
Its a given that for the most part we cannot run with antennas over 13' 6" in height (maximum height for highway tractors and their trailers in Canada), exactly the height of the antenna off the ground mounted on my mobile.
It goes without saying that the radiation resistance of your antenna will only be as good as how large or tall a whip your running on your favorite HF antenna.
Also pay attention to the the fact that the various antennas as seen throughout this gallery mounted on my mobile, are all center loaded (more or less) and are the most efficient type of HF antenna you can have mounted on your mobile.
With the coil located in the center of the antenna, the next thing you can do to increase the radiation resistance of the antenna, and limited by the height you can make the antenna, is too add a caphat to the very top of the whip, which will increase the capacitance and therefore the radiation resistance.
Remember that the radiation resistance of a vertical antenna can be improved on by adding to the electrical length of the antenna, and we can accomplish this by utilizing a caphat.
Of course it goes without saying that you also want to spend time on bonding the various panels of your mobile together, especially the horizontal panels.
This also has an effect on the radiation efficiency of your antenna system.
I had a great morning out playing radio on this day, although it was hard to keep my mind on working the bands, what with the wonderful soft lighting along with the clouds floating overhead reflecting the light from underneath, causing the sky to light up with a soft warm light that was painting the landscape with a wonderful pallete of color requiring me to put down the microphone and pick up my camera.
As is the norm for me on any given day at sunrise, I loved every moment of it, and plan on doing it all over again tomorrow and the next day and the day after that.
Click on the photo for a closer look.....
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