Archive for the ‘Toroids and Cores’ 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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2018-09-07 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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2018-04-22 Ferrite Loopstick Basics

From FB group Building Transistor Radios Then there is the loopstick. It is deliberately made long and thin to capture the RF magnetic fields. The frequencies that loopsticks are better at capturing are those that require long antennas that would be impractical. So the AM broadcast band is where loopsticks do their best. The loopstick’s

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2017-11-19 Royal 510 PCB hairline crack 

For FB group Vintage Transistor Radios  Speaking of fuzzy garbled audio…  I won another auction for a Zenith “Royal 510” which I’d never heard of.  It turned out to be a Royal 250.  The seller got no bids at all, so with less than a minute left I bid the minimum ten dollars. I got

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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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