How to Make HF Traps for Ham Radio
Ham radio has just a few truly essential components, one of them being the antenna. If you're a ham working multiple bandwidths but have limited space, you can use HF traps, which are combinations of resonant parallel coils and capacitors. Traps essentially keep circuits apart on the same real estate of the antenna, letting you get more bang for the buck on antennas that are 40 meters and below.
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Things You'll Need
- Lucite sheeting
- Grid-dip meter
- Ceramic capacitor rated at 6,000 volts
- Plastic solvent
- Soldering iron
- Good understanding of electronics principles
- 3-inch plastic disk
- Inductor made with No. 12 wire
- Egg or strain insulator
Instructions
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1
Fit loops of the Number 12 wire to one of the insulators.
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2
Place a capacitor in position on the antenna and connect it to the insulator using short leads.
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3
Solder these in place to temporarily keep them there while you work.
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4
Put the combined piece inside the inductor, which should have about 10 turns.
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5
Solder one end to an insulator-capacitor lead.
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6
Use the grid-dip meter to adjust the resonant frequency at this point.
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7
Use the station to check the g.d.o. frequency and make sure that the coupling between it and the trap is kept loose.
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8
Set the resonant frequency by making quarter turns to try to get to the chosen position.
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9
Assemble the trap now as part of the antenna now that you have set the frequency. You can attach the whole lengths of leads, if you're ready.
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10
Create a protective cover for each trap with two turns of lucite sheeting around the 3-inch disk, holding the disk at the center while you wrap. This creates a protective cylinder, the cover of which should be about 4 inches long. Use the plastic solvent to seal the edge to itself.
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11
Push out the disk once the solvent is dry. This cylinder can now house the trap.
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12
Put the trap in the cylinder and mark the ends where you will pass the antenna wires through.
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13
Drill the holes, push the antenna wires through and then seal around the holes with solvent.
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1
Tips & Warnings
If this procedure is too complicated for your skills, consider asking one of the "Elmers" at the local ham radio club for assistance. Chances are, there are others who have faced the same challenge of getting more bandwidth out of an antenna and have had to make HF traps themselves.
Don't attempt to make HF traps for your ham radio unless you have the electronics knowledge and skills that it requires.
