VE6AB Mobile Ops

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Antennas That Talk

This photograph shot of my mobile gives you a look at the 10-80 meter linear actuated tunesleeve antenna that I built some years ago for my previous mobile.

It goes without saying that gearmotor (screwdriver) antennas are at the top of their game, being able to switch bands while going down the road is a huge plus over monobander antennas that require you to stop and switch out coils for the different bands.

Now one part of the antenna that tends to get overlooked is the whip that resides up top of the coil assembly.
I see a lot of HF gearmotor (screwdriver) antennas mounted on mobiles that are being handicapped by too small a whip assembly. If you don't have a efficient whip assembly, good luck in being heard.
The whip assembly as seen mounted on my 10-80 meter antenna is a made up assembly consisting of a 5 foot fiberglass whip that started life as a Shakespeare 102" whip assembly.
Once I had the whip cut to a 5' length, I covered the entire five foot assembly with 304 stainless steel mesh tubing that terminates at the top with a fitting that allows for a 3' dia caphat to be mounted in place.
Until you utilizes a whip of this type on your favorite HF antenna, and make the comparison to your typical steel whip that most guys use, you have no idea as to what your missing out on, with the performance of the antenna a night and day difference.

Running a caphat is the best way of increasing efficiency in a mobile HF antenna, and remember the caphat goes at the very top of the whip.
The caphat added to the top of the antenna makes the antenna appear electrically larger by adding capacitance to the antenna and the more capacitance you add to the antenna, the higher the radiation resistance, and the higher the efficiency of the antenna.

On this day, It was fun to run with an antenna that is at the top of the hill when it comes to performance.

Expand the photo for a closer look.....

Here is a run down on the design and build of the antenna.....
https://www.jerryclement.ca/HamRadio/HamRadio/i-FTTMPzm