"Random Wire" Antennas
Perhaps the most misleading name in Ham Radio, "Random Wire" antennas are anything but random. They are specifically chosen lengths of wire that are intentionally not resonant on the Amateur bands. This is so that they can be resonant on many/all of the Amateur bands with the help of a tuner, a 9:1 balun and a 1:1 choke for good measure.
There were some very bright Hams (VE3EED, AB3AP who have done all the hard work in calculating the desirable antenna lengths. Check out those two links for more in depth information). The key was understanding that the antenna cannot be resonant on any half wave of any Amateur frequency. That said, here are "right" random wire antenna lengths in feet:
These are a pretty simple antenna to make. Cut your wire to these approved lengths and hook it up to a 9:1 balun and for a ground plane/counterpoise you need a 17 foot length of wire on the other side of the balun (laying on the earth). Connect a 1:1 choke right after the 9:1 and run your feedline to a tuner. You should be able to tune 10m-80m no problem, all with manageable SWR. It might be more than a rig tuner can contend with so count on using a dedicated tuner.
As a general rule, the longer you can make the Random Wire, the better. This of course depends on your operating location. If you are limited on space, a 29' vertical might work. If you've got more room and can use some of the longer lengths, all the better. You will pick up more gain.
A nifty portable hack for longer lengths is to use a steel tape measure. These are relatively cheap and compact. The 100' tape length can get you up to the 84' approved length or the 107' if you add a ~7' of extra wire. Alligator clips on a short piece of wire make it pretty easy to connect the balun to the tape measure. It's best to sand off the paint/coating from the tape at the desired length so the alligator clip makes a good contact.
This makes a simple and slick antenna for QTH or portable operating!
Thanks for checking out this build!
VE5REV 73!