Moose Jaw Amateur Radio Club

Resonant Wire Antennas with Screen Ground Plane

I've been using this system enough now that I feel confident in recommending it. It consists of a resonant 1/4 wave wire antenna paired with an aluminum window screen as the ground plane/counterpoise/mirror. It works so incredibly well and is so incredibly simple that it makes a fun and quick project for a new and seasoned ham alike.

The Wire

The wire is measured and cut for your band of choice. As an example, take 20m. You can do the math or use an app to calculate the 1/4 wave length. I always make them for the middle of the band so in this case, 14.175MHz or 16' 6 1/8" or 5.03m. I used 16 gauge primary wire because it was on hand. I made an end insulator out of Plexiglass to make it easy to string into a tree and give the wire a bit of stress relief. You can adjust the wire length to exact resonance with a Nano VNA or other analyzer. The wire is finished with a ring connector to help mount it to the connector.

The Connector

I made a connector out of a dollar store cutting board and an SO-239 socket. It has a couple wire connections for the driven element and the connection to the screen. You connect them with a wingnut making it easy to swap them out. You can also get a premade dipole connector and it will work just fine too. For for the screen connection it's a simple scrap of wire ~36" or so with an aligator clip soldered on. This allows for a really quick connection to the ground screen.

The Screen

This is where the magic happens. Conventional practice is to use ground radials to make up the "other 1/4" of the 1/2 wave antenna. And, when it comes to ground radials, the current thinking is lots of shorter radials are better than fewer longer radials. The only problem is that all ground radials are a pain, especially for portable use. They get tangled and people can trip on them; it's just not a pleasant experience. Enter the Magic Screen Ground Plane. This was popularized by Michael KB9VBR on YouTube. But after trying it, I can verify that it really works great for both resonant and non-resonant verticals. The aluminum screen has lots and lots and lots of shorter wires in a very compact footprint. It's like laying down a zillion radials at once with no fuss! This screen is 36"x84" aluminum window screen and is very pliable making it easy to handle and roll up for transport. It is available at Canadian Tire or home improvement stores. Just be sure it's aluminum and not plastic.

The Choke

The 1:1 choke is a necessity for keeping out the common mode current that can build up in the antenna. I have found that it lowers SWR too. Without out it I had a 1:2.6 SWR but with it I got the antena down to 1:1.0 in the middle of the band. I connected the 1:1 choke as close to the connector as possible, in this picture with a 12" coax jumper cable. I fed this antenna with 25' of RG8X coax.

The System

With the wire strung up into a tree or a pole, the ground wire connects to the screen that is simply laying on the ground. And, that's it! You don't need a tuner. It's resonant on your chosen frequency and with the obligatory fine adjustments, as this Nano VNA screenshot shows, it's pretty darn good:

It's a very slick system that is convenient and quick to deploy for mobile use like travel or POTA. You can cut other wires for the bands you want to work and swap them out as needed. I made 15m, 17m and 20m for my camping/POTA needs. I've tested this system with resonant and non-resonant antennas alike up to 40m with up to 100 watts of power and it works flawlessly through them all. As a first antenna, this will get you on the air cheaply, quickly and conveniently!