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Here is my homemade 1:1 HF Balun, balanced to Un-balanced
Core 4C6 Philips, Diameter = 36mm, height = 15mm, inside = 28mm
CU wire used 3x0.65mm wound read hard in parallel, and 3 of them wound on the core
The distance between the windings makes this balun close to 50 Ohm,
and the 3 cores in parallel gives a lot more outside surface, this lowered to loss.
The balance on the output is super nice looking at 3.5MHz
Here at 10Mhz minor phase drift, nothing really bad.
I measured the balance, using a fast scope, and two loading resistors to input ground.
Here is the schematic of my "Ruthroff's Balun", I used 13 windings
Windings are placed like on the schematic, 1-3-5 going ind on the top
and 2-4-6 comming out of the bottom, it is important that the input windings are placed together
to hold the impedance close to 50-60 Ohms.
Input to output loss, measured using my homemade wattmeter:
Literature about this:
Antennenbuch by Karl Rothammel (DM2ABK) 62.392
Transmission line transformers by Jerry Sevick (W2FMI) ISBN 0-87259-296-0
Here is another schematic of same 1:1 and a 1:4 balun
I am sorry I can not remember what this book is called, All I have is this picture.
This page is updated FEB 2005