Background & Research
I knew what I wanted...it had to "telescope" like a periscope since the intent of this antenna mast is for emergency GMRS communications during a disaster. Why have it deployed to 20' (max legal limit) when generally not using? I simply don't need it sticking up in the air all the time and I'm sure the neighbors would appreciate this approach. Telescoping made sense and initially I thought I could just pick one up on the cheap. Not true as real telescoping antenna masts are quite costly. Searching on the Internet produced antennas that cost thousands and kits that cost hundreds. I did however run into two particular sites that provided some great information.
First, I found in Google Books a scanned article from the Oct 1941 (yes, 1941...) issue of Popular Mechanics titled "One Man Telescoping Antenna Mast". Click here to view it. It's not attractive and uses guy-wires but it did get me thinking about building my own. Could I do it without the guy wires?
Then, I found Bob Bruninga's page where he designed his own telescoping mast out of used aluminum irrigation pipe. His design is great and really got me thinking as you can see from these two photos from his site (copied with permission). Check out the creativity he put into this pulley design. Both of our designs take advantage of the 3 to 1 leverage that this pulley design gives you.
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This looked simple enough and I knew I could build something similar to this. Turns out I did not have access to used aluminum irrigation pipe and quickly started thinking about electrical metallic tubing (EMT) from my local ACE hardware here in Alamo, CA. I also had to modify the pulley design to take advantage of the available materials at ACE.
