Ted Macklin (K4MPM) here!
I wanted to share some tips while they're still fresh in my mind about building one of those 4:1 Guanella Current Baluns. If you're thinking about tackling this project, which is awesome, believe me, these pointers will save you some headaches.
Just for a little context, this balun is a real workhorse.
It's an RF choke and transformer all in one, designed to take a higher impedance, like 200 ohms, and bring it down to 50 ohms. That's crucial for getting a better match with your transceiver and really improving your SWR.
From what I've learned, current baluns are definitely the way to go over voltage baluns—they give you better balance, fewer losses, and much better common-mode isolation. For the best results, you'll want a dual-core design using Type 43, 52, or 61 ferrite cores. Steer clear of those single-core voltage baluns! My build, for example, performed great from 1.7 to 173 MHz.
My Top Tips for Your Balun Build:
- Wire Length is Bare Minimum: I cut my wires to 33.5 inches. Trust me, that leaves you with a bare minimum of tails, so measure twice!
- Enamel Coating is a PITA: That enamel coating on the magnet wire? It's a pain to remove. I found that spinning pliers around the wire ends is the best way to clean it off. Do yourself a favor and do this before you start bending anything.
- Get Ready to Source Parts: I ordered the predrilled box with SS hardware, which was about $30.00, but I still had to track down my own "ring" lugs, core separator, fiberglass tape, zip ties, 14GA magnet wire, and PTFE Spaghetti! Just a heads-up so you're not surprised.
- Your Fingers Will Ache: Seriously. Working with that stiff wire and getting it to fit tightly on those squarish cores will make your fingers ache for 24 hours or more. It's part of the fun, though!
- Mark Polarity (and Double Check!): This is probably the most important one. Mark your wires for polarity and then double-check it again before you start attaching any wires. You'll thank me later.
I've got some attached pics from my build that I used as a guide, and they really helped visualize things. If you're diving into this, feel free to give me a shout. I'm always happy to talk shop!
Have funsies!
