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QRP/20w 4:1 Balun Instructions

Even the “QRP” kit will handle 50+ watts when used as a 1:1 balun. It makes a great dipole center. Here’s how to build it.

1.) Solder the Ground Jumper Pad

Create a solder bridge across the “GND” jumper pad.

2.) Attach Wire Stubs

Cut the length of poly stealth wire in half and strip about 1/8″ of insulation from one end of each piece. Insert into the PCB as shown.

Insert the stripped wire ends into the corresponding pads.

Solder into place.

3.) Wind the Toroid

Uncoil the magnet wire and start winding as shown, making 8 turns around the toroid.

Create a tap at 8 turns.

Continue winding 8 more turns in the same direction, parallel with the first set of 8 turns.

Trim the folded wire ends to about an inch long after you’re done winding.

4.) Attach the Toroid to the PCB

Strip enamel from the wire stubs if you don’t have a very hot soldering iron. If your iron gets up to 400 C / 750 F, you should be able to simply burn the enamel off of the wire with hot solder.

Insert the wire stubs into the toroid as shown. The single wire ends go to “GND” and “OUT”, and the twisted pair tap wire goes to “IN”.

Position the toroid near the board and solder into place. Hold the soldering iron on the pad for 5-10 seconds until the enamel burns off and solder flows throughout the joint. Trim the wires flush

5.) Attach the PCB to the BNC

Position the PCB flush with the tips of the connector and solder the center pin.

Reposition as necessary while heating the solder, then solder at least two of the ground lugs to the PCB. Flux helps. It takes a good amount of heat to get the solder to flow onto them (they are big heat-sinks).

6.) Install Hang Cord (optional)

Tie a short piece of cord (not included) to create a hang-point for the antenna.

7.) Install Heat Shrink Tubing

Place the 3/4″ (QRP) or 1″ (20w) heat shrink tubing over the matching unit and shrink into place.

Add some wire, and get on the air!