Archive for the ‘Transmitter’ Category:

2018-09-28 LM386 Used As Modulator of Final RF Output

From FB group Building Transistor Radios 2018-09-28 I see nothing wrong with using the ‘386 to directly drive the power output stage. It’s cheaper than a transformer. But I was thinking about how the current was flowing in the ‘386’s output transistors. Normally an electrolytic capacitor blocks any DC from flowing out of pin 5.

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2018-01-08 RF Oscillator For AM Band

For FB group Building Transistor Radios When I started building regen receivers, the first thing I found I needed was a simple  signal generator.  I have a function generator, but every time I want a different frequency, I had to readjust the controls.  So I built a few RF oscillators to put close to the

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2017-12-03 AM Oscillator Instead Of Aux Input

From FB group Vintage Transistor Radios  For the last few months, ever since I started experimenting with oscillators on the AM broadcast band, my attitude towards auxiliary audio inputs has changed.  Earlier I thought  that it would be convenient to have an aux input.  But I was leery of making changes to the collectibles radio

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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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2017-01-15 Tuned Circuit Tester

I’m building a tuned circuit tester, which is a Franklin Oscillator without the parallel tuned circuit.  I based it on the schematic I found at this URL.  The first amp is a JFET in common drain or source follower configuration, which then drives the 2nd stage, a PNP transistor in common base configuration, so there

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2016-09-29 FM Quality Stereo Tx

When I googled I found a ‘stereo input’ FM transmitter. Most of the FM ‘bugs’ on the web and YouTube have a microphone.  The circuit I linked to has left and right inputs, but mixes them to make a monophonic (not stereo) signal.  After looking at the schematic I noticed a mistake, so I thought

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