Gerard's Elex Homebrew

99
Item nr.

Elex Homebrew Dipmeter

A dip meter is used for all kinds of frequency measurements.

**Data for Elex Homebrew**
Production	The Netherlands, 1988.
Bands	100kHz to 40Mhz in seven bands.
Semi- conductors	2x BF451 (osc.), BFR91 (measurement), 2x BB212 (varicaps), 78L10 (voltage stabilizer).
Cabinet	White plastic. Size 12x18.5x4 cm. Weight 450 gr.
Power	Batt 2x9V.
Documents	Schema.

The Design

The dip meter contains an RF oscillator with the coil external so that it can be coupled inductively to other circuits. What you can do is: place it in the vicinity of a tuning circuit (which need not be operative!), tune the frequency, and observe at what frequency occurs a small dip in the meter reading. The tuned frequency is the resonance frequency of the unknown circuit. By combining an unknown coil with a (known) capacitor, the dip meter is used for measuring coil inductance. Keep the unit close to a playing radio until it whistles and you know the frequency your radio is receiving.

Coil value Band range

10mH 0.1 - 0.25MHz

2.2mH 0.2 - 0.47MHz

470uH 0,45 - 1.08MHz

100uH 1 - 2.4MHz

22uH 2 - 4.9MHz

4.7uH 4.3 - 11MHz

1uH 9 - 22.5MHz

0.22uH 15-40MHz

The coils are quite simple RF chokes, mounted on eighties-styled speaker connectors. Because of the control range of the varicap, the "width" of one band ranges over a factor of about 2.5. By making each coil about one fifth of the previous coil, the start and end of each band is a little more than the double of the previous band, so the bands overlap a little.

Coil value	Band range
10mH	0.1 - 0.25MHz
2.2mH	0.2 - 0.47MHz
470uH	0,45 - 1.08MHz
100uH	1 - 2.4MHz
22uH	2 - 4.9MHz
4.7uH	4.3 - 11MHz
1uH	9 - 22.5MHz
0.22uH	15-40MHz

Obtained	9/1998 from Piet Hoen.
Condition	8.
Disposed	Scrapped 4/2020.

This Object

The meter was built by Piet Hoen long ago, but he gave it to me because he thought I would be able to carry out more complicated things with it. This happened to be true, but I don't use it very much either. One can make the dial as simple or as complicated as you like. Piet went through all bands with a radio and marked the observed frequencies on a piece of paper.

The circuit board inside the unit is quite small. Most of the space inside the box is empty, some is taken by the batteries and the meter.

Part of Gerard's Radio Corner.
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