Ham Radio 40 / 20 / 15 Meter Half Wave Fan Dipole Antenna

The Experiment: In this experiment were going make a Ham Radio 40m 20m 15m Half Wave Fan dipole. One’s that working will add the 80m section.

80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-photo

Table of Contents
1. Part List
2. Prototype
3. Notes
4. Conclusion
5. Reference Links


Part List:

1. Center Tee Connector
2. 14 Gauge Wire
3. Two 4-1/2″ plastic Spacers
4. Two 1/2″ PVC end isolators
5. Two – 96.74uhuh Loading coils
6. One – Spool #18 Magnetic wire
7. One – 8 foot 1-1/4 underground S40 rigid PVC conduit

^Top


Prototype:

Build the 40-20-15 meter Fan Dipole
Step 1. Cut two 36′ section of #14 wire.
Step 2. Cute two 16′ section of #14 wire.
Step 3. Strip 2″ off one end of 20/40 meter #14 wire sections (Note twist the wire tight).
Step 4. Solder on the Ring/Spade terminal.
80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-connection
Step 5. Attach the 20/40 meter #14 wire section to the center tee.
80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-center-tee-connection
Step 6. Cute two 4-1/2″ spacers.
Step 7. Drill wire feed throw holes in spacer. (See Drawing)
ham-radio-80-meter-loaded-40-20-15-meter-half-wave-fan-dipole
Step 8. Tread the #14 20/40m wire section through the wire spacers. (See Drawing)
Step 9. Position inner spacer 2″ from the center Tee. (See first Antenna photo)
Note:  wrap some electrical tape on each side of the spacer to keep it in place.
Step 10. Position second spacer 16′ out from the center Tee on the 20m wire.
Step 11. Solder a Ring terminal on the end of the 20m wire to keep it in place.
Closer-up view of how the 40m wire thread’s through the center spacer.
80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-center-spacer2
20m tuning stub will attach to the Ring terminal.
80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-center-spacer2
View of the center spacer in the air 40m wire on top/center, 20m wire on the bottom.
Step 12. Install the end isolator on the 40m wire.
80-meter-coil-loaded-40-20-15-meter-half-wave-fan-dipole-end-isolator
Then raise the antenna at least 20′ off the ground and go through the normal tuning procedure.

Adding the 80 meter section


Step 1. Cut two 4.75in S40 rigid gray PVC coil cores
Step 2. Follow the diagram and wind 68 turn on the coil core
Step 3. Connect the 80m loading coil to each end of the 40m section
Step 4. Connect 5 feet of AWG #14 wire to the open end of each coil
Step 5. Connect a 2feet of AWG #14 wire though the 80m coil to the 40m terminal
Step 6. Tune the 40m section first then the 80m section

Note: See diagram in Step 7 above.All measurements are approximates. Coil inductance shoul be somewhere between 96.00 – 110uh.
^Top


Notes:

The Position of the middle spacer is not critical, I just positioned it almost in the center of the 40 meter section.

At 20 feet up, the 20m antenna will tune down to a 1.0-1 swr, on 40m it won’t but if the center of the antenna is raised to 30″ the swr will be less then 1.2-1 swr on 40m.

The nice thing about this fan dipole is that the middle spacer keeps the 20m section nice and tight. The key to this is the way the 40m wire is threaded through the middle spacer.

I have been using the 80/40/20 meter version for many year and it has been a one of the best antennas in the air.
^Top


Conclusion:

The 20/40/15 meter fan dipole works really well. It receives well on 20/40/15 meter.

^Top

Reference Links:

1. Dipole Antenna Calculator
2. Inch Fraction Calculator
3. LC Resonance Calculator
4. Coil Inductance Calculator
5. Helical Coil Calculator
6. Coil Designer
^Top

Advertisements