How to Make a Very Efficient Double-Tuned, Four-Band, MW Crystal Radio Set using two Version ‘b’ Single-Tuned, Four-Band, MW Crystal Radios

Quick Summary A double-tuned four band crystal radio set (DT4BCS) can be created by coupling together two Version ‘b’ single tuned crystal radio sets (VbST4BCS). See Article #22. Selectivity and sensitivity are essentially constant over the entire AM broadcast band because of the use of ‘Venodyne’ constant bandwidth antenna coupling, resonant impedance control and band…

How to measure the electric-to-acoustic transduction power loss of magnetic and ceramic earphone elements, with measurements of some headphone receiver elements

Quick Summary This Article describes a device and procedure for measuring the sensitivity of earphone elements. Its purpose is to provide a quantitative method for comparing elements. Elements may be easily sorted for application to listening to weak signals, as in crystal radio sets. Actual measurements of an assortment of elements is provided. Measurements The…

A Zero Loss, Unilateral ‘Ideal’ Audio Transformer Simulator

A Zero Loss, Unilateral ‘Ideal’ Audio Transformer Simulator, plus… This device makes is very easy to determine the optimum audio transformer source and load resistances for any crystal set diode/headphone combination. No test equipment necessary Quick Summary This device works as an audio transformer when connected between the output of a diode detector and headphones,…

Quantitative insights into Diode Detector Operation derived from Simulation in SPICE, and some Interesting new Equations relating diode parameters to weak signal sensitivity

Quick Summary Several new equations are presented showing various relations between diode detector rectified current, input AC and output DC power, insertion power loss and the ‘Linear-to-Square-Law Crossover Point’ (LSLCP). The LSLCP is an operating point where the diode detector is operating half way between its linear and square law modes. It can also be…

New ways to Increase Diode Detector Sensitivity to Weak Signals, and a way to determine if a diode detector is operating above or below its Linear-to-Square-Law Crossover Point

Quick Summary The very low signal sensitivity of a crystal radio set can be improved by cooling the diode. This possibility arises when the rectified DC current is below about twice the Saturation Current of the diode. Also see Article #28 for more info on increasing weak-signal sensitivity. Definitions of terms to be used: Plsc(i)…

Get 3 dB more Output for Greater Volume on Strong Stations plus

Quick summary Over the years many experimenters have realized that one could get “free” power from a crystal radio set and operate an amplifier with it. This has been successfully done by coupling an additional tuned circuit and detector to the antenna and tuning it to a strong station. The rectified DC from the station…

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