Even before entering the mystical realms of UHF design, radio frequency (RF) circuits come with a whole range of fun design aspects as well. A case in point can be found in transmission line transformers, which are commonly used in RF power amplifiers, with the Guanella transformer (balun) being one example. Allowing balanced and unbalanced (hence ‘balun’) systems to interface without issues, they’re both very simple and very complex.

Transmission line transformers are similar to regular transformers, except that the former relies on transmission line action to transfer energy rather than magnetic flux and provides no DC isolation. The Guanella balun transformer was originally described by Gustav Guanella in 1944. Beyond the 1:1 balun other configurations are also possible, which [Dr. Arar] describes in a follow-up article, and which are also covered in the [FesZ] video, alongside the explanation of another use of Guanella transformers: as an impedance transformer. This shows just how flexible transformers are once you can wrap your mind around the theory.

https://www.youtube.com/watch?v=QAYaetJ1dvM

https://m.youtube.com/shorts/OzaO2ZvvJxM?si=0nFJilizS2o-zhTw&fbclid=IwAR2AannlYXI85Tz-uLOIvLKMcgs1HnyUXeZ17P07hhys9MSmJpPWZrbg3uQ

This video shows one method I use to wind toroidal inductors and transformers. The real trick is often how to hold the toroid core while doing the winding of the wire. The plastic toroid fixture shown is available from http://www.qrpme.com. I also give a few details on how to strip the enamel insulation, and then test the inductor when it is complete. There are many, many useful websites that contain toroid data, including composition, type, size, materials, winding factors, calculators, and more.

In this video I help you understand how Common-Mode Chokes work, showing some that you can easily build for yourself.
I also show you how to evaluate the performance of a Common-Mode Choke using a very simple test jig.
00:05 Introduction Common-Mode Chokes: How do they Work?
00:16 What is the idea behind a Common-Mode Choke?
02:03 CHOKE DESIGN #1: Simply Increasing the Inductance of the outer skin of our Coax
02:27 METHOD #1: Wrap the coax around a ferrite toroid or rod
03:08 THE EXPERIMENT: One Turn at a Time
04:17 OVERALL PREFORMANCE
04:55 METHOD #2: Slide Lots of Ferrite Beads on your Coax
07:08 CHOKE DESIGN #2: Using the Parallel Resonance of your coil of coax
11:24 EVALUATING THE PERFORMANCE OF A COMMON-MODE CHOKE
14:13 Final Comments and Toodle-oots!

How to Identify an Unknown Ferrite Core
https://www.youtube.com/watch?v=Q95Vwk3kZok

Do you have a ferrite core, but don’t know what it is? Follow along with Mike Arasim, Product Manager for Power and Inductive Applications at Fair-Rite Products as he identifies two unknown Fair-Rite EMI suppression beads using basic, inexpensive, readily available equipment in a very not temperature controlled environment.

Test equipment used: Keysight 1733C LCR Meter. Flir DM93 Digital Multimeter. Mitutoyo Absolute Digimatic 6” Caliper. 10 turns of 26awg solid wire.

https://www.fair-rite.com/toroid-calculator/

Edit: turns out this was a faulty cat5 plug.
Cleaning up a 4 way video balun/filter module in the process of fault-finding my camera system.

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