Archive for the ‘Schematics’ Category:

2020-01-01 VA3IUL Website RF Projects

I spent too much time looking at the schematics and projects at this website.  Lots of interesting things to download.https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Homebrew_RF_Circuit_Design_Ideas.htm

2018-09-02 Mims Mistakes In Audio Amplifier

From FB group Building Transistor Radios, 2018-09-02 I already see one mistake. On p.27, Audio Mixer. The R6 is only 1k. The voltage divider R5 and R6 will give a voltage less than 0.6 at Q1’s base, which means Q1 will not be forward biased enough and the circuit won’t work or else sound distorted.

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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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2018-03-28 Wideband RF Amp In Royal 500s

From FB group Ferrite Loopstick Antenna Experimenters Some experimenters in another group looked at schematics and saw that some radios with a RF amplifier between the loopstick and the converter used a third section on the variable capacitor to tune the RF amplifier. This is good, but it makes the variable capacitor more expensive and

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2017-08-15 1950s Astor 7 Transistor Radio

2017-08-07 Protoboards And Bypass Capacitors

From FB post One important thing that people forget to do is consider what might happen with a circuit that has anything that draws power from the protoboard. If you’re working with a few low power devices such as small LEDs and switches, then there is usually not a problem. But if you have a

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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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2000-01-01 watsonspics.blogspot.com

This is a link to my pictures I posted. watsonspics Pictures, for the most part, of schematics I’ve drawn, using ExpressPCB, free software. There is little or no text. A few may have been drawn by others. Those from Quantsuff (quantsuff.com) have a QS in the name. I’ve received permission from QS to use them.

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