Ham Radio Coat Hanger Antenna

Stuck in quarantine? Want to make an antenna but don't want to risk the hardware store? Look no further!

This is a 1/4 wave ground plane antenna kit I designed around an SO239 connector and things you can find around your house. This antenna was designed to be used in the 2m VHF band, but you can adjust the lengths of the driven/radial elements for use in other frequencies.

Materials you will need:
1x SO-239 Chassis Connector
1x Vertical Stabilizer (.STL included)
1x Horizontal Stabilizer (.STL included)
4x Ring/Fork Terminal
4x #6 x 1/2" Sheet Metal Screw (or similar)
4x 4" to 6" zip tie (or similar)
1x 19.25" Driven element (steel coat hanger or solid copper wire)
4x 21.5" Radial elements (steel coat hanger or solid copper wire)
1x Spray paint (Optional)

Directions: (See Antenna Assembly Drawing PDF)

1. Place the SO-239 connector into the Horizontal Stabilizer

2. Solder the driven element to the center conductor of the SO-239 connector

3. Feed the driven element through the Vertical Stabilzer

4. Use the four #6 Sheet Metal Screws to attach the Horizontal and Vertical Assemblies. Do not tighten all the way. Allow enough space to insert the ring terminals in the next step. (Tip: Briefly heating the screws with a soldering iron or lighter will make it easier for the screws to cut threads in the plastic)

5. Crimp and solder each radial element to a ring terminal and insert each so that they are sandwiched between the SO-239 and the Vertical Stabilizer

6. Tighten the screws from Step 4 until each ring terminal feels secure. Do not over tighten. Ensure each radial makes good electrical contact with the connector. Use a continuity tester if you have one.

7. Bend each radial to match the profile on the Horizontal Stabilizer (~45 deg) and use the four zip ties to secure each radial in place using the slots on each arm of the Horizontal Stabilizer. (If you are using stiff coat hanger, you can pre-bend these before inserting them in Step 5)

8. If you have an antenna tuner/SWR meter, I would recommend checking your antenna before using it. It should be very close already, but you may need to trim it a little bit.

I mounted the antenna to the end of 1/2" PVC conduit pipe with a small piece of inner tube and a hose clamp. The pipe is mounted to a 4x4 on my 3rd floor apartment patio with two more, larger hose clamps. There are a million different ways to do this, but these are things I already had. You may also want to consider spray painting the antenna to resist corrosion and UV degradation.

So far, this antenna has worked pretty well. I'm regularly able to reach repeaters 30-40 miles away with good signal reports. We've had two hail storms in the last two weeks, a ton of high winds, and all the local birds like to hang out on the radials. So far so good!