I hate to admit it, but lately, I’ve been getting a lot of my ideas for blog posts from Reddit posts to /r/amateurradio. The first post asked whether or not you should fold over the braid when making a flowerpot antenna. I had never heard of a flowerpot antenna, so I did some searching.
The flowerpot antenna is so-called, I think, because the base of it is often inserted into a flowerpot to make it a stealth antenna. It is basically a half-wavelength length of coax inside a PVC pipe to obscure its actual purpose. At the bottom of the antenna, the coax is wrapped around the PVC to make an RF choke. The first post to come up in my search describes a 2-meter flowerpot antenna designed by VK2ZOI.
The reddit post actually asked about a 10-meter version of the antenna. I found a design on VK1NAM’s blog. The 10-meter antenna is, of course, a lot longer than the 2-meter antenna, so instead of a length of PVC pipe, this design uses a telescoping mast to support the antenna.
If you have some RG-58 lying around, or perhaps find some at a ham swap meet, this looks like a fun antenna to play with.
Not technical? Read this.
While searching for information on the flowerpot antenna, I happened to run acrosss Understanding Antennas For The Non-Technical Ham. This book was written by Jim Abercrombie, N4JA (SK) and is now freely available on the web. It lives up to its name, offering descriptions for commonly-used HF antennas in language about as non-technical as it can be. It’s worth every penny. :)
Books by Jerry Sevick, W2FMI
Jerry Sevick, W2FMI, was renowned for his work on short vertical antennas and transmission line transformers. Over the years, he wrote many articles and books on baluns and ununs, and many hams consider his book, Building and Using Baluns and Ununs: Practical Designs for the Experimenter, to be the bible on the topic. He received the Dayton Hamvention Technical Excellence Award in 2005 and became an SK in 2009.
This morning, I came across a reddit post asking for information on a short vertical antenna. Since I happen to have a copy of W2FMI’s The Short Vertical Antenna and Ground Radial, I did a search for where to buy a copy. Amazon had some used copies, but at ridiculous prices, so I continued my search.
Fortunately, I found it in the Digital Library of Amateur Radio and Communications, which is part of the Internet Archive. And, it’s available for free!
Sevick’s two other books, Building and Using Baluns and Ununs: Practical Designs for the Experimenter and Transmission Line Transformers can be borrowed from the Internet Archive’s library.
Have fun and make some antennas!
The flowerpot antenna is a coaxial dipole, also called a sleeve dipole. The outside of the shield is one element, terminated by the choke. The inner conductor, stripped of the shield, is the other element.
Vertical dipoles of this design are common in commercial installations, though they aren’t made of coax. They have low wind loading, are easy to mount, and are omnidirectional. They have better radiation towards the horizon than a ground plane antenna.
Overall, a good antenna design that is well-understood.
https://en.wikipedia.org/wiki/Coaxial_antenna
Understanding Antennas For The Non-Technical Ham looks interesting, but it is a shame it is in such an awful font (Times New Roman Bold). I’m tempted to take the whole thing and learn how to create an ePub book that is actually readable.
I agree 100% about the font. I may email N4UJW and ask if I might do a re-layout.
I made one for 6m band and it is pretty good antenna for sure. A bit tricky to tune for best SWR but once you get it, in tune just use lots of tape and zipties to get everythng in position.
Coaxial sleeve dipoles are nice antennas. Easy to build for sure.