Publisher & Editor-in-Chief
Leo Simpson, B.Bus.
Editor
Greg Swain, B.Sc.(Hons.)
PUBLISHER'S LETTER
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Darren Yates, B.Sc.
Reader Services
Ann Jenkinson
Sharon Macdonald
Marketing Manager
Sharon Lightner
Phone (02) 979 5644
Mobile phone (018) 28 5532
Regular Contributors
Brendan Akhurst
Garry Cratt, VK2YBX
Marque Crozman, VK2ZLZ
John Hill
Jim Lawler, MTETIA
Bryan Maher, M.E., B.Sc.
Philip Watson, MIREE, VK2ZPW
Jim Yalden, VK2YGY
Bob Young
Photography
Stuart Bryce
Editorial Advisory Panel
Phillip Watson, MIREE, VK2ZPW
Norman Marks
Steve Payor, B. Sc., B. E.
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. A.C.N. 003 205 490. All
material copyright ©. No part of
this publication may be reproduced
without the written consent of the
publisher.
Printing: Magazine Printers Pty
Ltd, Alexandria, NSW; Macquarie
Print, Dubbo, NSW.
Distribution: Network Distribution
Company.
Subscription rates: $42 per year
in Australia. For overseas rates, see
the subscription page in this issue.
Liability: Devices or circuits described in Silicon Chip may be
covered by patents. Silicon Chip
disclaims any liability for the infringment of such patents by
manufacturing or selling any such
equipment.
Editorial & advertising offices:
Unit 1a/77-79 Bassett Street, Mona
Vale, NSW 2103. Postal address:
PO Box 139, Collaroy Beach, NSW
2097. Phone (02) 979 5644. Fax
(02) 979 6503.
ISSN 1030-2662
2 Silicon Chip
Back to the superheterodyne
The month, we feature the first part of a 2-part constructional project for
an AM broadcast radio using the standard superhet circuit. This is being
featured for the benefit of TAFE college and secondary school students, beginners in electronics and anyone who wants to learn about or refresh their
knowledge of the most important communications circuit – the superhet.
We have had this project in mind for a while, conscious that this side of
electronics has been neglected for quite some time. Back in the days of valves,
every beginner "cut his teeth" on a crystal set and then went on to build a
small valve radio. In doing so, he would come to grips with the principles
of AM radio and the superheterodyne. In fact, by the time the enthusiast of
those days had mastered the principles of the superhet, he was well on the
way to being well-versed in electronics.
These days the field of electronics is far more diverse and much bigger
than anyone could have dreamed of 30 years ago. And so with the passing
of valves and the takeover of electronics by semiconductors and integrated circuits, the good old AM superhet radio has been shunted out of the
limelight. So much so, that probably a fair proportion of today's enthusiasts
would admit, if pushed to it, that they are not familiar with the superhet.
Well now is the time to correct that deficiency.
Nor should readers think that superhets are somehow old fashioned or
obsolete. The superhet in all its forms is in wider use than ever, in all TV
and radio receivers, hifi tuners, amateur radio and communications gear in
all fields, in radio control and so on. The difference today is that so much
of the circuitry is buried in ubiquitous ICs and so there is little chance to
trace a signal through all stages.
The special feature of the AM Radio Trainer in this issue is that the top
of the printed circuit board is actually screen printed with the circuit diagram and you insert each component onto the board in the exact position
of the circuit symbol. We have designed it this way so that the constructor
will have a more "hands on" feel for the circuit. At the end of it all you will
have a working radio in which the signal path can easily be traced through,
stage by stage. That can't be done in any standard pocket radio because the
components are crammed too close together and there is liable to be damage
if you make the attempt.
The article starts on page 12 of this issue. Go to it.
Leo Simpson
| 
