Electronics

REVIEW OF THE RJ-1 vs B&Z SE-10 BOOSTER

OUR TEST/REVIEW OF THE RJ-1 HEADPHONE/SPEAKER BOOSTER AGAINST THE POPULAR B&Z SE-10 BOOSTER.

 

Heathkit Groundtrack GR-1290 VLF metal detector

All resistors are 1/4 watt, 5% tolerance and all capacitors are in microfarads (uF) unless marked otherwise.
Voltages were taken with a 9 Volt supply and a setting with no sound coming from the speaker.
The controls were set as follows:

Heathkit Cointrack GD-1190

All resistors are 1/4 watt, 5% tolerance and all capacitors are in microfarads (uF) unless marked otherwise.
Voltages were taken with a 9 Volt supply and a setting with no sound coming from the speaker.
The controls were set as follows:

Simple BFO Metal Detector Schematic Diagram

This simple BFO metal detector requires only a few of components and an evening’s work. The two oscillators are simple Colpitts designs using BJT transistors. The reference oscillator’s frequency is approximately 370kHz, slightly tunable with the help of a silicon varactor diode. The outputs of the two oscillators are fed to a mixer made with Q3 and Q4.