cr vacuum tube detector radio

Posted on Feb 6, 2014

A basic detector radio set that uses a vacuum tube instead of a crystal detector. This radio requires few components, and because it`s inherent simplicity it is easy to build. In spite it`s simplicity this receiver performs well if a high-strung long wire, well-insulated antenna is available, or strong stations are nearby. A short-w

cr vacuum tube detector radio
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ave version works great almost everywhere whenever wave propagation is good. Parts list for this simple vacuum tube detector radio: B1 - 1. 5 Volt Dry Cell C1 - Rotary Capacitor - 500 pF (pico Farad) C2 - Filter Capacitor - 1 nF, used with magnetic phones only D1 - Diode - Diode, Vacuum Tube Detector L1 - Antenna coil - 75 turns 180 uH (micro Henry) R1 - Load resistor - 200 K, used with crystal phones only Coil L1 on Picture 1 is hand wound in a universal style to reduce coil capacitance. It is wound on a 1/4-inch diameter coil form, outfitted with a good (low loss) RF ferrite tuning screw. The antenna coil L1 is 75 turns preferably with 10x0. 05 MM Litz wire, with taps at 15, 30 and 45 turns. These taps marked 2 and 3 on the schematic diagram, and they are useful for improved impedance matching. Coil inductance need to be around 200 uH with a 500-pF C1 capacitor Litz wire is a specially insulated multi-strand RF magnet wire; it has 10 strands, each 0. 05-millimeter diameter. The more conductors a Litz wire has the better. With smaller wire size, it gets progressively harder to remove the enamel from all the tiny strands for soldering. There are several commercial preparations available for just such purpose, they works well if not exactly fast. Litz wire with low temperature insulation can be tinned directly, as the enamel melts off during soldering. Since multi-strand wire increases the wire`s surface area, it helps to...

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