History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Issues/1944 09

P.03 - Contents Banner

The Australasian Radio World

Devoted entirely to Technical Radio

and incorporating

All-Wave All-World DX News

Vol. 9. - SEPTEMBER, 1944 - No. 4

P.03 - Publication Notes

Proprietor - A. G. HULL

Manager - Dudley L. Walter

Secretary - Miss E. M. Vincent

Short-wave Editor - L. J. Keast

For all correspondence: City Office - 243 Elizabeth St., Sydney - Phone MA2325

Office Hours - Week-days: 10 a.m. - 5 p.m., Saturdays: 10 a.m. - 12 noon

Editorial Office - 117 Reservoir Street, Sydney

Subscription Rates - 6 issues 5/3, 12 issues 10/6, 24 issues £1, Post free to any address

Service Departments - Back Numbers, 1/- ea., post free; Reply-by-mail Queries, 1/- each

Printed by Bridge Printery Pty. Ltd., 117 Reservoir Street, Sydney, N.S.W., for the proprietor of the "Australasian Radio World," 117 Reservoir St., Sydney (Footnote P.28)

P.03 - Contents

CONTENTS:

CONSTRUCTIONAL -

The "Ferrier" Super Crystal Receiver . . . . 10

A Non-Microphonic Volume-Expander Circuit . . . . 13

Simple and Effective Valve Tester . . . . 15

TECHNICAL -

N.Z. Radiomen to go to Britain . . . . 5

The Design of Direct-Coupled Amplifiers . . . . 6

Eclipse Staff Holds Amplifier Contest . . . . 11

A Buzzer Makes an Handy Multivibrator . . . . 12

Radio Frequency for Industrial Heating . . . . 16

SHORTWAVE REVIEW -

Notes From My Diary . . . . 23

New Stations . . . . 23

Shortwave Notes and Observations . . . . 24

THE SERVICE PAGES -

Answers . . . . 26

P.03 - Editorial Notes

Editorial

Right in the midst of a lot of discussion about amplifiers there has been dropped a regular "block buster", full details of which we hope to reveal in next month's issue. Following closely on the heels of statements about "amplifiers beyond reproach", and "perfect direct-coupled amplifiers", a completely new and revolutionary circuit has come to hand. This circuit is so unconventional as to appear absurd, but is actually a definite step in the right direction and full of the most amazing possibilities. In a nutshell, it has been found that output impedance problems are solved if the output of a valve is taken by placing a load on the cathode circuit, instead of plate circuit. Tremendous loss of gain is incurred, but in these modern times this is of little importance, compared to the improved fidelity possible. As an example, an output valve required about twenty volts of signal input for ordinary use, but under the new operating conditions will require a signal input of 150 volts. One application of the scheme is for inter-stage coupling, using a cheap audio transformer, which then gives performance comparable with that of a super-duper high-fidelity one. Practical work with the new circuit has proved highly interesting and results are right up to expectations. Working with an audio transformer which cost 6/6 we have been able to get quality reproduction of a high standard, at the same time obtaining the advantage of low resistance in the grid circuit. This is highly desirable, but hard to achieve with resistance-capacity coupled amplifiers. - A. G. HULL.