I’m sitting on the grass in the back yard and it’s chilly, but the sunlight feels really good on my back. I can hear some birds up in the trees, I’m waiting to see if they’ll come down and eat some birdseed. I started thinking about a way to watch them up there. What I
(Read More…)
MP3 Player To FM Radio Link (Mono) This circuit allows you to play your MP3 or any stereo audio source into a mono signal for reception on an FM radio. It has no antenna and has a range of a dozen or so meters. It operates off a 6 volt rechargeable Ni-MH battery pack but
(Read More…)
For years the HF bands were filled with RF interference that would appear at a frequency for a minute and then jump to another frequency. The direction the pulses were coming from was the Soviet Union. There was no way to stop the interference; the Soviets were ignoring complaints. This YouTube video tells about it
(Read More…)
This is a low power oscillator using an air core coil and silver mica capacitors for stability. Parts values are subject to the frequency needed. There is no modulation. For FM the 10 pF capacitor would be lower and include a reverse biased diode as a varicap in parallel. The audio should be across this
(Read More…)
Good article on passive intermodulation, AKA the Rusty Bolt Effect. https://www.electronics-notes.com/articles/radio/passive-intermodulation-pim/what-is-pim-basics-primer.php
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.
(Read More…)
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
(Read More…)
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
(Read More…)
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
(Read More…)
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
(Read More…)
