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HF Antenna Micro-Traps – DIY Build Project

This is the one you’ve been waiting for – the traps to go with the micro End Fed Halfwave (EFHW) antenna build. Here’s how to make them.

These traps will work with my Ultimate Ultralight EFHW ( or just about any QRP end-fed halfwave antenna, and you could even build pairs to use with a dipole.

– LC Resonance Calculator:
– Toroid Winding Calculator:

You’ll certainly need some MATERIALS:
– T37-2 Toroids (my usual):
– T50-2 Toroids (a little more efficient and maybe easier to build):
– 28 ga Magnet Wire:
– 39pF 100v Ceramic Capacitor (0603 case recommended):
– 62pF 100v Ceramic Capacitor (0603 case recommended):
NOTE: Consider a few other capacitors in the 22pF – 100pF range, depending on the traps you’d like to build.
– Perforated Prototype Board:
– 5/8″ Heat Shrink Tubing:
– 1/4″ Heat Shrink Tubing:

And you’ll need some TOOLS:
– Dremel (or similar)high-speed rotary tool:
NOTE: I have had my Dremel tool for about 25 years now and it hasn’t missed a beat. Based on my personal experience, I would recommend going with the name brand tool.
– Diamond Cutting Wheels:
NOTE: I really like these because you can’t cut yourself with them, but they cut the perf board and BNC connector brass just fine.
– Soldering Iron (any will do) with a fine tip:
NOTE: I’ve been using this one for about a year with no issues. The heat gun is AWESOME for hot air/solder paste construction. The iron works well for traditional soldering.
– Electronics Tweezer Set:

Please share your builds with me when you’re done, and tell us about how it works out for you in the comments below.

de K6ARK