QRP Reel Antenna for 20M

Description

This is a (likely over-engineered) QRP antenna system I've been working on for a while. The goal was to have something that was easy to deploy/pack and was somewhat self-contained. The design does not include a balun, but I haven't found this to be a problem, particularly when operating in the wilderness.

Compact, All-In-One Design:

• Element reel doubles as antenna insulator
• Guy lines are stored on the center hub that nests in the element reel
• Stakes do triple duty as stakes, a handle for the reels, and clips to hold the reels together for travel

Full size photos

Parts List

Printed Parts

• antenna-body.stl (x1)
• antenna-cap.stl (x1)
• hub.stl (x4)
• reel.stl (x2)

Non-Printed Parts

Amazon links provided, but some parts may be easier to source at a local hardware store

• 608 Bearings (x2)
• 1/16in Shock Cord (at least 20ft)
• Stainless Swivels (x2)
• BNC Panel Connector (x1)
• 22GA Wire (~20M)
• 3/16in Zinc Plated Rod (12in)
• 1/2in Hook & Loop Cable Tape (2 12in pieces)
• Small Carabiner (x1 - Optional)

Assembly

Printing

Print the required number of each part using your desired material and settings. The only part that should require any supports is the reel, and it should only be needed in the cavity where the elements will wind. I've found the supports to be fairly easy to remove when printed in either PLA or PETG, with PETG being slightly more difficult.

Hub Assembly

1. Start by pressing a 608 bearing into one hub piece, then press another hub piece onto it making sure the holes on both sides of the hub are aligned. The pieces are designed to be a tight fit, so a vise will likely be needed for this step.
2. Tie one end of the shock cord through the small holes on the hub and wrap until you've got your desired amount. I've found around 10 feet works well, but be sure not to store the shock cord (guy lines) under tension so they keep their elasticity.
3. Tie a swivel on the other end of the guy line. This will be used to clip the guy line to the reel/insulator.
4. Insert the hub into the reel. It should snap in securely due to the nubs printed in the reel. Ensure the hub seats securely and can be removed, then repeat for the other hub.

Stakes

The stakes are made simply by cutting 2 6in lengths of 3/16in rod, clamping the last 1/2in in a vise, and bending to approximately a 90 degree angle.

Antenna

1. Push the panel mount BNC connector through the large hole in the antenna body, and secure it and the shield tab in place using the provided nut.
2. Cut the appropriate length of wire for your antenna. The reel is designed to hold approximately the correct amount for a 20M antenna using 22GA wire.
3. Feed one of the wire elements through the small holes (there are 3 holes to allow for strain relief; route the wire in, out, in), then solder it to the center connector.
4. Repeat step 3 with the other element, but solder it to the shield tab.
5. Cut a small (~4in) length of the 22GA wire and feed it through the top of the antenna cap. Twist it together to create a loop. Attach the carabiner here if desired.
6. Screw the cap onto the body. The cap should come down past the bottom of the body. This is to ensure that any rain that may fall on the cap doesn't drip down the feed line.
7. Run the other end of each element through the small holes in the reel (the reel doubles as the insulator.
8. Wrap the elements around their respective reels.
9. Clip the reels together using the stakes (see pictures).
10. Wrap cable wrap around the reels to hold everything together.

11.Optional: The antenna body is designed so that, after tuning and testing, it can be filled with casting resin to create a very weatherproof housing.

Print Settings

Printer Brand:

Creality

Printer:

Ender 3

Supports:

Yes

Notes:

Supports only needed for the reel

Category: Electronics