Archive for the ‘Receiver’ Category:

2019-02-05 Floating Detector Diodes Are Not A Good Design.

from FB group Building Transistor Radios 2019-02-05 Graeme Heal Aaron Cake has a lot of good circuits and projects. But this one uses the ‘floating detector diode’ with no DC return path, so the circuit will only work if the diode’s leakage current provides the discharge. That means the diode must be germanium, not silicon,

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2019-01-27 Replacing Corroded Battery Contacts

From FB group Building Transistor Radios 2018-01-27 Many of the radios I’ve acquired were so corroded that I had to replace metal parts. I used tin can lids to make replacement battery holder contacts. The steel is springy enough to hold cells in place. Scissors can cut the steel, and it can be drilled and

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2019-01-07 TRF Receiver Experiment

2018-01-04 also FB group Building Transistor Radios I thought that the ‘tinkerers’ who were tinkering with the loop antennas may have been getting a stronger signal because the loop antennas have a large area to capture the RF signals, so I decided to make a single channel AM Band receiver, and I chose KNX 1070

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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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2018-12-31 Zenith Royal 500 Unique Issue

Also to FB group Building Transistor Radios 2018-12-31 I have several Zenith Royal 500 radios with the ‘long range’ eighth transistor added as a RF preamplifier (chassis number begins with 8). See the attached photo. This does not require a third section on the tuning capacitor, as some ‘TRF’ radios have. Zenith added a tuned

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2018-12-09 Selectivity V. Sensitivity

from FB group Building Transistor Radios 2016 Dec 9 Jim Glover An ideal receiver would have a bandpass shaped like a square wave where the bandpass is flat with no attenuation and the attenuation is infinite outside of the passband. In the real world this isn’t possible but any receiver buyer with the money would

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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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2018-11-25 One Transistor FM Receiver Schematic Part 1

From FB group Building Transistor Radios Larry Daniel 2018-11-26 This is the original schematic posted by Larry. GM is a gimmick capacitor made of two short lengths of solid hookup wire, twisted together for a few pF capacitance. List of RF Chokes for the ham bands Larry said he used an RCA SK1008, then corrected

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2018-11-19 Depth of Loop Antenna

from FB group Building Transistor Radios 2018-11-19 I shared my loop antenna – see photo, and it is somewhat 2 dimensional. The arms are 762mm across but the depth of the windings is only about 35 mm. Compare that to the ferrite loopstick at the other extreme, it’s 10 mm diameter but 100 mm long.

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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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