Archive for the ‘Building projects and kits’ Category:

2020-10-15 Irrigate With Moisture From Air

I’ve seen so many locations in Southern California that are pretty much barren mostly because the country is lacking water. The cost of water in So. Cal. is high because there are so many people that the water they need has to be imported from hundreds of miles away — as far as Northern California.

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2020-07-11 DIY Off Grid Solar System

This is a YouTube video. This guy did a very good job of building an off-grid solar system. It’s transportable, uses four 100 watt panels, two 12V AGM batteries in parallel, can supply 120VAC pure sine wave at 2000 watts and costs under $1,900. This is an excellent video with plenty of details. He calls

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2020-06-10 Dubbing Adapter

This is an adapter to connect a source such as a smartphone stereo headphone output to the input of an MP3 recorder. The view and diagram is looking at the back of the adapter where the plugs are inserted into the jacks. The switch handles are on the far side. The switch on the right

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2020-05-28 Solid State Shortwave RF Preselector

Comment left 2020 May 29 on YouTube video in the title. This video covers MOSFET, dual gate MOSFET, JFET and BJT tuned preamps (preselectors) for his shortwave crystal radio. “The talk about using 18 volts for the cascode got me thinking about tube designs. When the plates need 100+V, and when the heater to cathode

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2020-04-19 Ultrasonic Transceiver Design Idea

Many years ago I saw electronic listening devices for receiving a block of ultrasonic frequencies that bats use and downconvert that block to frequencies that humans can hear. But no one to my knowledge has tried to convert human frequencies up to ultrasonic frequencies so that humans can try to establish a conversation with other

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2020-03-29 AM Osc + Modulation + Buffer

This is from Electronics Illustrated Projects 1968. It shows crystal sockets, but instead a RF coil may be used and its value will be about 220 microhenrys. And C1 and C2 will have to be changed to bring the frequency down to the AM band. The germanium transistors are no longer available so silicon transistors

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2020-01-30 Royal 200 Silicon Conversion, Part 3

Also to FB group Vintage Transistor Radios I finally drew the line and said I’m finished fiddling with this Zenith Royal 200 and put it back together. I got it without knobs or handle, and with all the transistors missing. It’s not pretty, and the speaker cone is warped and sounds bad. This is the

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2018-09-11 Vectronics Aircraft Radio Kit

I got the Vectronics VEC-131K aircraft band radio kit in the mail yesterday and warmed up the soldering iron to assemble it. It came at a decent price, so some of my complaints seem to be cost cutting measures. It comes with a decent assembly instruction manual, but some of the pages including the schematic

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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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2018-08-29 High Temperature And Nylon Screws

From FB group Hobby Electronics, 2018-09-01 I faced this dilemma before. I’ve repaired power supplies where the transistor failed because it was not held tightly to the heat sink because of a nylon screw that got hot. I used a steel screw and a fiber washer, and heat shrink tubing over the threads to insulate.

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