Getting Technical

Articles on technical subjects that don't fit elsewhere

How does a Radio Work?

The simplest radio to demonstrate and understand is a "Crystal Radio". A crystal radio has no amplifiers and only one tuned filter.


Fig. 1: Schematic of  1920s style Crystal Set with High Impedance headphones (moving iron or moving coil).
The 2000 Ohms earphone acts as resistor to set the capacitor discharge time constant.



Fig. 2: Schematic of  1930s style Crystal Set with High Impedance Piezoelectric or "crystal" earphone.
The ceramic earpiece is equivalent to a 2nF to 20nF capacitor (depending on Model)

Internet Streaming

First we need some background to understand the inherent limitations of the Internet and the fundamental difference between Internet information and true Broadcast.

Though local wired computer networks and ISP fibre/cable etc can do "broadcast" connections from a server to you, the Public Internet and WiFi actually have to open a unique stream for each user. If there are are 10,000 viewers then 10,000 times as much connectivity and bandwidth is used. Even at the Broadcaster's server. Though if the Broadcaster puts a server at each of your own ISP's local "nodes" (or Exchanges for DSL on phone lines) the bandwidth per server is reduced. This is very expensive.

With true broadcast on cable, fibre, local cat5e wiring, Satellite, Terrestrial (Analogue or Digital) and MMDS it makes no difference at all to cost or bandwidth if there are 10 viewers or 10 million viewers.

PIC supported by JAL

As of 13th September 2011 JAL supports

Valves or Tubes

Introduction to Valves

A vacuum tube, electron tube (in North America), or thermionic valve (elsewhere, especially in Britain) and Röhre in German (Adjective/Plural? Röhren as in Röhrenradio = Valve  Radio),  usually simply called "tube" or "valve", is a device that uses wires, grids and plates to change current flowing between the heated cathode (source) and collecting Anode. 

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Vacuum Fluorescent Displays (VFD)

Vacuum Fluorescent Display (VFD)

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Magic Eyes

Commonly available Magic Eye valves (Tubes)

Also search for: Magisches Auge on eBay "worldwide". Also note German speakers "Röhrenradio" = "Vintage Radio"

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Neon Indicators, Nixies and Dekatrons

Neon Indicators

  1. Neon gas filling at low pressure. (90V to 180V strike, 55V to 80V sustain). No filament.

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Michael Watterson's picture

Vintage Indicators

Special Indicators (Vintage)

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Switching power supplies

Articles (mostly Wikipedia)

    Inductor types:

Greyshaw Instruments CR50 Bridge

What is it?

It's a Test Instrument that measures Resistor or Capacitor values to about 10% accuracy.

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