First homemade antenna

This entry was posted by on Saturday, 11 September, 2010 at

I take business trips about 6 times a year now — never more than 2 or 3 days at a time. But now that I’m a radio ham, I love to take the hobby with me to random hotel rooms. For the last few trips, I’ve carried a little handheld VHF/UHF walkie-talkie, and this allows me to meet new hams within a few miles radius. But now that I’ve been learning morse code, I’m excited to create a real long-distance setup that I can effortlessly tote in my backpack on these hotel trips.

What are the main ingredients? Very simple:

  • a tiny low-power radio, 5 watts or less (called “QRP” in the ham-verse)
  • a set of morse-code paddles and electronic keyer
  • a portable antenna capable of picking up lonnnnnng wavelengths (like 20 or 40 meters)

The first two things aren’t a big problem; I’ve already been practicing morse code on my paddles, and there a zillion tiny radios to choose from that I can buy. But a portable long-distance antenna? That’s a black art. Luckily I found this very cool site that describes a homemade antenna that folds up into a three ring binder for transport! It’s basically a bunch of parts from Radio Shack and Office Depot, strung together cleverly. After a week, I’ve got it all built. You’ve got two 5′ lengths of wire hanging horizontally, meeting together into a middle connector:

…and each wire end is terminated by a crazy hanging transparency covered with zig-zagging copper foil:

…because the zig-zag copper foil tape is on both sides of the transparency, you get a full 20′ length of accordioned copper on each end! Here’s the whole antenna strung across the width of my basement ham shack:

…and then a 15′ twin-lead feedline is run from the centerpoint and plugged into a balun on an antenna tuner (whose job is to automatically match impedance between radio and antenna for a given transmission frequency.)

Yes, of course, it’s insane to do a first test drive in the basement, but I was too lazy to string the thing outside my window late at night. This antenna will really be strung across hotel rooms, hopefully on as high a floor as possible. But even with crappy basement RF reception, I was still able to immediately hear morse code conversations on 20 and 40 meter bands. And for the first time in my life, I was able to hear conversations on 80 meters as well! (My current outdoor antenna only does 20 and 40 meter.) This was also my first experience with an antenna tuner, and I was amazed to watch it ker-chunk and auto-tune whenever I transmitted 5 watts on different frequencies. Nobody was able to hear my transmissions, but hey, it was in a basement. And the thing didn’t smoke or catch on fire. 🙂