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Author Topic: KJ7U Screwdriver Antenna  (Read 1373 times)
KB9RHA
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Posts: 15




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« on: December 31, 2003, 08:04:49 PM »

I just received my new KJ7U Screwdriver antenna and am anxious to install it. I am considering homebrewing my own control unit for it utilizing a BASIC Atom microcontroller and interfacing it to my IC-706. There is one thing, I'd like to modify the antenna. Smiley It's just my nature that I have to try and make something better than it already is.

There is a magnetic switch installed that counts every 1/4 turn of the motor, however, there are no upper and lower limit switches. I emailed KJ7U and was told they are only a source of trouble. It's not that I don't believe him, but I'd still like to look into it. The other thing I'd like to do is replace the existing motor with a stepper motor.

My question is, has anyone successfully disassembled this antenna and was able to reassemble it? Any input would be greatly appreciated.

One other thing, any suggesstions on how to mount the antenna to a 2000 Honda Civic? Cheesy

73,
Christopher Zeman, KB9RHA
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K0BG
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Posts: 10248


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« Reply #1 on: January 01, 2004, 12:35:56 PM »

Adding limit switches to a screwdriver antenna is problematic for several reasons. Contrary to popular belief, there is RF impressed on the motor control wires. This can and does cause RFI problems if the wires are not properly bypassed. Adding additional wiring for limit switches would exacerbate the problem.

As for stepper motors, I suspect this has been done, but I haven't read about anyone doing it. Most of the stepper motors I've seen are too large for the average mast.

Instead of going to the trouble modifying a commercial one, build one yourself. The ARRL's Antenna Compendium #7 has two articles on building your own screwdriver.

Alan, KØBG
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