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 (https://youtu.be/s-_LyhdGapM) or just about any QRP end-fed halfwave antenna, and you could even build pairs to use with a dipole.
– LC Resonance Calculator: https://www.omnicalculator.com/physics/resonant-frequency-LC
– Toroid Winding Calculator: http://www.66pacific.com/calculators/toroid-coil-winding-calculator.aspx
You’ll certainly need some MATERIALS:
– T37-2 Toroids (my usual): https://amzn.to/3hFsYlj
– T50-2 Toroids (a little more efficient and maybe easier to build): https://amzn.to/2QCkGio
– 28 ga Magnet Wire: https://amzn.to/3b9Isf4
– 39pF 100v Ceramic Capacitor (0603 case recommended): https://www.digikey.com/product-detail/en/kemet/C0603C390J1GACAUTO/399-15862-1-ND/7516362
– 62pF 100v Ceramic Capacitor (0603 case recommended): https://www.digikey.com/product-detail/en/kemet/C0603C620J1GAC7867/399-14992-1-ND/7382541
NOTE: Consider a few other capacitors in the 22pF – 100pF range, depending on the traps you’d like to build.
– Perforated Prototype Board: https://amzn.to/2YLsFOJ
– 5/8″ Heat Shrink Tubing: https://amzn.to/3lwwGjt
– 1/4″ Heat Shrink Tubing: https://amzn.to/2G9bGzk
And you’ll need some TOOLS:
– Dremel (or similar)high-speed rotary tool: https://amzn.to/3gFEkEL
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: https://amzn.to/2QBRHve
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: https://amzn.to/2GaENlN
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: https://amzn.to/2ENy00w
Please share your builds with me when you’re done, and tell us about how it works out for you in the comments below.