Archive for the ‘Reflex’ 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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2019-01-05 Substituting Chokes For A Coil In A Reflex Circuit

From FB group Building Transistor Radios 2018-01-15 Nick wants to use two 10 mH chokes close to each other in place of a coil that’s used in the typical reflex circuit. I’ll include a schematic of the circuit (from somewhere on the net). This is labeled L2. (begin my comment) Nick Bastian The coupling is

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2018 Dec 8 Sinclair Book 22 Tested Circuits Using Micro Alloy Transistors

from FB group Building Transistor Radios 2018 Dec 8 Nick Bastian posted the schematic of a Sinclair Micromatic radio. I found the book by Clive Sinclair about the circuits using micro alloy transistors. Germanium transistors and especially micro alloy transistors are no longer made so it’s better to use silicon BJTs instead. Here is the

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2018-11-07 The 2 Transistor Boy’s Radios

from FB group Building Transistor Radios 2018 Nov 7 I bought some 10 uF, 10 volt MLCC (multilayer ceramic capacitor) capacitors, which do not have the electrolyte so they can’t dry out. They are smaller, too. If they are used for replacements, then radios might last much longer. About the only thing left to go

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2018-07-25 How Stable Are Regen Reflex Radios?

From the FB group Building Transistor Radios Regenerative / reflex designs are not as stable as superheterodyne radios. One problem is the design depends on factors that are not predictable such as gain and feedback, which are not linear. The regenerative reflex depends on the circuit being on the verge of oscillation, which is not

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2018-07-24 “Boy’s Radio” Reflex Schematic

From FB group Building Transistor Radios Willie Barnett I see from the schematic that this is a reflex regen. They did something else that is very seldom seen, the volume control acts not as a normal variable voltage divider, but instead as a variable shunt load across the secondary of the driver transformer. This is

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2018-07-24 “Boy’s Radio” Reflex Schematic

From FB group Building Transistor Radios Willie Barnett I see from the schematic that this is a reflex regen. They did something else that is very seldom seen, the volume control acts not as a normal variable voltage divider, but instead as a variable shunt load across the secondary of the driver transformer. This is

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2018-06-20 Don’t Ask To Share Software!

From FB group Arduino Projects Marcos Tulio Junior I think it is unethical for others to expect the coder to reveal his IP (intellectual property). There is nothing wrong with asking the coder for a link to open source software. But you are out of line when you expect others to do for you what

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2018-03-26 Reflex Receiver, 2 Transistor

For FB group Building Transistor Radios Darrell Darby (Schematic below) What amazes me is the collector load resistor for the earphone stage is 100k. That’s more than ten times higher than usual, and it’s okay because the crystal earplug is very sensitive. I would squeeze a bit more gain out of it by removing the

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