“ANTENNA QUESTIONS!”

What sort of frequency are we talking about? It sounds like you want to tune the antenna to a specific frequency, but is it 1.5 MHz or 1.5 GHz?? There is only about 1000 to 1 difference.

Tell us more about the application.

Sincerely

Bill

High Sierra makes antennas for the amateur radio community that will tune 3.5-50 MHz range. One will need an additional coil to go down to the 1.8MHz range. They have a 12vdc motor which moves the antenna up and down to tune on your desired frequency. I use one on my car and talk around the world going down the road. Their concept might help you with your needs. Here is a link: http://www.hamcq.com/index.php

GERARD18,

Your question is very vague. What is available depends to a great extent on what your parameters are for length, extended and collapsed, how many sections, whether each section should tapered or be straight, etc.

Also, do you require that the telescoping action be done by hand or remotely by electric or other power source?

Also, please explain your "screw shaped ridges". A sketch would be nice. Bit-map images and photos (JPEG) may be uploaded using the camera icon in the toolbar of the reply box. If you wish only to raise one section above another for tuning by changing the effective coil length, then the High Sierra antenna mentioned above (a so-called "screwdriver antenna" design) would work very well for HF frequencies, but is not very efficient, since it is a coil-loaded design.

Please bear in mind that a true telescoping pole, tube, whatever, must, by definition, have all sections collapse inside one. Therefore each section must be smaller than the last, and having both inside and outside threads requires a much thicker wall. A better alternative, for manual operation, is to have a spring loaded pin at the bottom of each section, with a matching hole near the top of the section below it. This allows a positive lock to support the weight of the higher sections. Some poles rely simply on the friction fit between tapered sections, or a locking nut over threads at the top of each section which creates friction by tightening the slotted end.

There are really many choices.

What is the application for your antenna?

Almost every automobile on the road has an automated telescoping radio antenna. Not sure about the screw shaped ridges -- what is the purpose of them?