Archive for the ‘Inductors’ Category:

2019-03-07 Make a 4 Millihenry RF Choke

From FB group Building Transistor Radios Mar 7 I got some of these toroid cores a few months ago, and I got around to experimenting with them. I wound one with 21 inches (51 cm) of 30 AWG (.25 mm diameter) enameled wire. This covered the core with a single layer of wire. I measured

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2019-03-06 Ferrite Toroid Cores 61 Mix

from FB group Building Transistor Radios 2019 Mar 5 I bought a bunch of ferrite toroid cores: Fair-Rite 5961001101 have 61 ferrite material and they’re about $.50 from Arrow.com. They’re 1/2 inch (12.7mm) OD and 1/4 inch (6.35mm) high. The edges are rounded so they don’t scrape off the insulation of the fine wires. The

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2018-11-26 Two 6 uH RF Chokes

from FB group Building Transistor Radios 2018-11-26 https://archive.org/stream/ETIA1983/ETI%25201983-03%2520March_djvu.txt Two 6 uH RF chokes The photo shows two different RF chokes, each about 6.4 microhenrys. The one on the left is a ferrite bead, made by Fair-Rite, Cat. # 2643000801. These were about 12 cents apiece from Mouser.com. Yes, the wire passes through the small hole

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2018-09-07 Q of an Inductor

from FB group Building Transistor Radios, 2018-09-07 Tom Miller Say a capacitor or inductor has a Q of 100. The losses are about 1/100 of the energy in the component. In a tuned circuit the capacitor Q is usually much higher than this – it has lower losses, so the more important is the Q

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2017-06-02 I Built Another Oscillator For AM BCB

I pulled a pill bottle out of my junk box, it had a single layer of solid enameled wire wound on it, and it measured 85 microhenrys.  So I added the transistor, resistors and the capacitors to get it to oscillate at the low end of the AM BCB, around 540 kHz. The schem is

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2016-09-05 Ferrite Cores At Radio Frequencies

I have always thought that using ferrite toroid cores for radio projects at HFs and above was not necessary, because all of the RF circuit parts lists call for low permeability powdered iron cores. I’ve never given it much thought; about the only thing that crossed my mind was that the powdered iron cores may

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2016-06-05 Toroid Cores 10 mm .4 Inch Green

I was on eBay and saw some small green ferrite toroid cores, ten for 99 cents including shipping.  I figured that since I had bought some larger green cores a few weeks ago and liked them, I couldn’t go wrong buying these since they were less than ten cents apiece. They were sent from an

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2016-06-04 Crystal Radio Coils, Crystal Diodes

I was reading some of Geo John’s projects and came across a crystal radio set that he built using two tuned coils. A crystal radio set refers to the type of detector used, which was once a galena crystal and a ‘catwhisker’ to find a sensitive spot on the crystal. Nowadays, that is no longer

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2016-05-28 The Five For A Dollar Toroid Core Is Back

A few years ago the Joule Thief fans and others built many projects with a very popular toroid core that was sold from Electronic Goldmine, a surplus electronics company, for the affordable price of five for a dollar.  Eventually the supply was all sold and it was no longer available.  The stock # was G6683.

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2016-05-16 Tape Wound Toroid Core From Surplus Sales

Long ago I built DC-DC converters using a toroid made with tape wound core. The cores were about 2 inches O.D. and we used regular 12 AWG solid insulated house wire for the primary windings. Even so, these cores vibrated a lot at several hundred Hz, making a screeching noise. I saw some very small

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