QEX_2005_05.pdf

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Forum for Communications Experimenters

May/June 2005

Issue No. 230

KD6OZH’s Multi-Output Power Supply

ARRL

225 Main Street

Newington, CT USA 06111-1494

The national association for

AMATEUR RADIO

Technical Topics Scrapbooks

Prefix Guide

Technical Topics Scrapbook

1995-1999

This is the third compilation of 'Technical

Topics' articles, produced by popular demand.

'Technical Topics' is by far the most successful

regular column in the RSGB's journal RadCom

and we are pleased to be able to present the

article's pages in this handy book, together

with a new index. If you have an interest in

radio and electronics, you will find this book a

fascinating read.

ARRL Order No. RT95 $29.95

Sale $25.95 Save $4

Prefix Guide

The new edition still includes all the

elements that have made the book so

popular over the years such as the

DXCC deleted entities, Russian & CIS

entities etc. With this edition the book

has had many new elements included

for the first time. The popular DXCC

checklist has been added along with

details of various award programs

IOTA, CQ WAZ, DXCC, WAS and

others.

This book is an excellent tool for the

beginner and the experienced hand

alike. Designed with a "lay flat" wire

binding for ease of use the new "Prefix

Guide" is a must for every shack

ARRL Order No. 9046 $19.95

Sale $16.95 Save $3

Technical Topics Scrapbook

1990-1994

This 2nd compilation includes all the words,

pictures and line drawings from the most

popular column in the RSGB’s magazine

RadCom. Pat Hawker’s blend of clippings from

other publications and contributed material is

linked by his own unique commentary,

enriched by a lifetime of being interested in the

technical aspects of radio, both professionally

and as a radio amateur.

ARRL Order No. 7423 $25.95

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Practical Wire Antennas

Wire antennas offer one of the most cost-

effective ways to put out a good signal on the

HF bands, and this practical guide to their

construction has something to interest every

amateur on a budget. Full details of feeding

and matching are included, making each

antenna easy to set up and use successfully.

Theory has been kept to a minimum - instead,

the author has shared his years of experience

in this field, offering ‘down to earth’ advice that

will be appreciated by beginners and

enthusiasts alike. No-one who builds and uses

wire antennas can afford to be without this

handy guide.

ARRL Order No. R878 $17.00

CLOSEOUT $9.95 Save $7

Technical Topics Scrapbook

1985-1989

A collection of all of the very popular Technical

Topics articles by Pat Hawker, G3VA,

published in Radio Communication magazine

during the years 1985 to 1989. Pat has

produced a wealth of ideas, modifications, and

tips for the radio amateur for many years, and

this book contains a sample of his contribution

to amateur radio in the most popular RadCom

column of all time. This book could well provide

that vital 'spark' for your next project!

ARRL Order No. RT85 $19.95

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Other Titles

Antenna Experimenter's Guide

ARRL Order No. 6087 $34.95 Sale $29.95 Save $5

Radio & Electronics Cookbook

ARRL Order No. RREC $34.95 Sale $29.95 Save $5

The Antenna File

ARRL Order No. 8558 $34.95 Sale $29.95 Save $5

RSGB Technical Compendium

ARRL Order No. RTCP $34.95 Sale $29.95 Save $5

Antenna Toolkit 2

ARRL Order No. 8547 $49.95 Sale $42.95 Save $7

Your Guide To Propagation

ARRL Order No. 7296 $19.95 Sale $16.95 Save $3

The RSGB Guide To EMC

ARRL Order No. 7350 $34.95 Sale $29.95 Save $5

RSGB IOTA Directory

ARRL Order No. 9314

$19.95 Sale $16.95 Save $3

HF Antenna Collection

ARRL Order No. 3770 $34.95 Sale $29.95 Save $5

VHF/UHF Handbook

ARRL Order No. 6559 $34.95 Sale $29.95 Save $5

The Low Frequency Experimenter's Handbook

ARRL Order No. RLFS $34.95 Sale $29.95 Save $5

HF Antennas For All Locations

ARRL Order No. 4300 $34.95 Sale $29.95 Save $5

Low Power Scrapbook

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International Microwave Handbook

ARRL Order No. 8739 $39.95 Sale $34.95 Save $5

Practical Projects

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International Antenna Collection

ARRL Order No. 9156 $19.95 Sale $16.95 Save $3

International Antenna Collection 2

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Continued on Inside Back Cover

INCLUDING:

About the Cover

An inside view of John Stephensen’s

versatile power supply.

The article begins on p 17.

QEX (ISSN: 0886-8093) is published bimonthly

in January, March, May, July, September, and

November by the American Radio Relay League,

225 Main Street, Newington CT 06111-1494.

Periodicals postage paid at Hartford, CT and at

additional mailing offices.

POSTMASTER: Send address changes to:

QEX, 225 Main St, Newington, CT 06111-1494

Issue No 230

Harold Kramer, WJ1B

Publisher

Doug Smith, KF6DX

Editor

Robert Schetgen, KU7G

Managing Editor

Lori Weinberg, KB1EIB

Assistant Editor

L. B. Cebik, W4RNL

Zack Lau, W1VT

Ray Mack, WD5IFS

Contributing Editors

Production Department

Steve Ford, WB8IMY

Publications Manager

Michelle Bloom, WB1ENT

Production Supervisor

Sue Fagan

Graphic Design Supervisor

Mike Daniels

Technical Illustrator

Joe Shea

Production Assistant

Advertising Information Contact:

Janet L. Rocco, Account Manager

860-594-0203 direct

860-594-0200 ARRL

860-594-0303 fax

Circulation Department

Kathy Capodicasa, Circulation Manager

Cathy Stepina, QEX Circulation

Offices

225 Main St, Newington, CT 06111-1494 USA

Telephone: 860-594-0200

Telex: 650215-5052 MCI

Fax: 860-594-0259 (24 hour direct line)

e-mail: qex@arrl.org

Subscription rate for 6 issues:

In the US: ARRL Member $24,

nonmember $36;

US by First Class Mail:

ARRL member $37, nonmember $49;

Elsewhere by Surface Mail (4-8 week delivery):

ARRL member $31, nonmember $43;

Canada by Airmail: ARRL member $40,

nonmember $52;

Elsewhere by Airmail: ARRL member $59,

nonmember $71.

Members are asked to include their membership

control number or a label from their QST when

applying.

Features

3 A PIC-based HF/VHF Power Meter

By Roger Hayward, KA7EXM

11 A New Design Approach for 40-Meter Yagis

By J. V. Evans, N3HBX

17 A Multi-Output Power Supply for the Experimenter

By John B. Stephensen, KD6OZH

21 Short Low- and Medium-Frequency Antenna

Performance

By Valentino Trainotti, LU1ACM, Senior Member, IEEE

and Luis A. Dorado, Member, IEEE

44 Measuring Cable Loss

By Frank Witt, AI1H

48 Octave Calculations for Amateurs

By Maynard A. Wright, W6PAP

51 Receiver Audio Processing Using a Phase-Locked

Loop

By Robert Kavanagh, VE3OSZ

56 Using the SA605/615 IF Processor IC

By Dan Doberstein

Columns

61 Out of the Box

62 Tech Notes

62 Next issue in QEX

63 Letters

In order to ensure prompt delivery, we ask that

you periodically check the address information

on your mailing label. If you find any inaccura-

cies, please contact the Circulation Department

immediately. Thank you for your assistance.

May/June 2005 QEX Advertising Index

American Radio Relay League: Cov II,

20, 61, Cov III, Cov IV

Atomic Time: 60

Down East Microwave, Inc.: 50

Expanded Spectrum Systems: 20

J-TEC, LLC: 10

National RF: 50

Nemal Electronics International, Inc.: 16

Noble Publishing Corp.: 16

RF Parts: 55

Teri Software: 50

Tucson Amateur Packet Radio Corp.: 47

Watts Unlimited: 20

League Inc. For permission to quote or reprint

material from QEX or any ARRL publication, send

a written request including the issue date (or book

title), article, page numbers and a description of

where you intend to use the reprinted material.

Send the request to the office of the Publications

Manager ( permission@arrl.org )

May/June 2005 1

THE AMERICAN RADIO

RELAY LEAGUE

Empirical Outlook

The American Radio Relay League, Inc, is a

noncommercial association of radio amateurs,

organized for the promotion of interests in Amateur

Radio communication and experimentation, for

the establishment of networks to provide

communications in the event of disasters or other

emergencies, for the advancement of radio art

and of the public welfare, for the representation

of the radio amateur in legislative matters, and

for the maintenance of fraternalism and a high

standard of conduct.

ARRL is an incorporated association without

capital stock chartered under the laws of the

state of Connecticut, and is an exempt organiza-

tion under Section 501(c)(3) of the Internal

Revenue Code of 1986. Its affairs are governed

by a Board of Directors, whose voting members

are elected every two years by the general

membership. The officers are elected or

appointed by the Directors. The League is

noncommercial, and no one who could gain

financially from the shaping of its affairs is

eligible for membership on its Board.

“Of, by, and for the radio amateur, ”ARRL

numbers within its ranks the vast majority of

active amateurs in the nation and has a proud

history of achievement as the standard-bearer in

amateur affairs.

A bona fide interest in Amateur Radio is the

only essential qualification of membership; an

Amateur Radio license is not a prerequisite,

although full voting membership is granted only

to licensed amateurs in the US.

Membership inquiries and general corres-

pondence should be addressed to the

administrative headquarters at 225 Main Street,

Newington, CT 06111 USA.

This Way to the Great Ingress

P. T. Barnum might have thought he

could do it better; but now, ours is the

“greatest show on Earth.” The world’s

biggest hamfest ( Dayton ) hosts the

2005 ARRL National Convention, in

its most outstanding incarnation yet.

Here’s why.

You can meet ARRL staff and vol-

unteers, including as our new COO

and Publisher, Harold Kramer,

WJ1B.There’ll be a special ARRL area,

where you can chat with writers and

editors of our publications, start or re-

new your ARRL membership and get

free gifts.

The Dayton Amateur Radio Asso-

ciation will conduct Amateur Radio

license examinations. Visit www.

arquillalabs.com/license.html or

e-mail Terri Ruwe, AK8T, at ak8t@

arquillalabs.com for more informa-

tion or to make an appointment. The

National Association of Radio and

Telecommunications Engineers will

conduct commercial license exams.

Information and registration are avail-

able at www.narte.org .

Don’t miss the outstanding forums.

Among the technical gems are the Kit

Building Forum, with Joe Eisenberg,

KØNEB, and a Broadband-over-Power-

Line (BPL) Forum with David Yoder.

Stick around for Sunday morning’s

Technology Task Force Forum, too, be-

cause you’ll hear and see Joe Taylor,

K1JT, discuss his JT65 digital protocol

for weak-signal work. One of today’s

most engaging speakers reveals the

rationale behind his invention, which

offers robust performance over disper-

sive paths. We’ll also have an update

on adaptive DSP techniques for beam-

forming, digital voice and other areas

in communications.

Point your Web browser to www.

hamvention.org for other details.

Don’t forget to bring your raincoat—

see you there!

We’re pleased to report many out-

standing technical articles waiting just

offstage here at QEX . Many concern a

perennially popular topic: antennas. Al

Christman, K3LC, sent us a study of ra-

dial ground systems, for which he plans

to write a second part. Former QEX Edi-

tor Rudy Severns, N6LF, promises an

article on measuring properties of the

earth beneath your antenna. Why guess

when you can measure? L. B. Cebik,

W4RNL, will continue enlightening us

about particularly interesting designs

and modeling software. Ron Skelton,

W6WO, will describe an antenna that

puts you on 40 m without consuming all

your acreage.

Plenty of circuit-design articles are

coming your way, too. In the battle

against receiver noise, you’ll find

K1MC, Mal Crawford’s variable-

frequency oscillator design at the front

lines. Rod Brink, KQ6F, will address

noise-related and other performance

issues of his new direct-conversion

architecture. Fred Brown, W6HPH,

will show us how to build his home-

brew noise-figure meter.

The challenges of receiver testing re-

main on the front burner. As technology

rapidly advances, so must our testing

methods advance. Comparisons between

old and new must account for those

advancements. To wit, Ulrich Rohde,

N1UL, will expound the nuances of

modern receiver testing, in general.

Those articles are but a few that you

can expect in the coming months.

Thanks to all writers for your support

of QEX . We’re counting on you!

In This Issue

Roger Hayward, KA7EXM, brings us

an accurate power meter using an

Analog Devices AD8307 logarithmic

amplifier and a PIC 18F452 microcon-

troller. It’s a neat addition to your

shack that’s available in kit form.

J. V. Evans, N3HBX, delivers a new

approach to 40-m Yagi design.

John Stephensen, KD6OZH, returns

with a multiple-output power supply

design. Single-supply circuits may be

elegant, but power-supply techno-

logy increasingly diminishes the need

for them. Our broadcast engineer-

ing friends from Argentina, Tino

Trainotti, LU1ACM, and Luis Dorado,

wrote recently about top-loaded vertical

antennas. We reproduce their work

here with the gracious permission of

Jacqueline Hansson and IEEE.

Frank Witt, AI1H, delivers improved

methods for measuring cable loss.

Maynard Wright, W6PAP, covers a piece

of free software, GNU Octave , that cuts

the time required for certain design cal-

culations. Bob Kavanagh, VE3OSZ, pre-

sents an outboard PLL processor that

helps receivers lacking DSP to dig CW

signals out of the noise. Further along

the processing vein, Dan Doberstein de-

scribes the SA605 and 615 IF processor

ICs and their applications.

In “Tech Notes,” Ron Skelton,

W6WO, takes a look at evaluating

speech quality objectively— 73, Doug

Smith, KF6DX, kf6dx@arrl.org .

Telephone: 860-594-0200

FAX: 860-594-0259 (24-hour direct line)

Officers

President: JIM D. HAYNIE, W5JBP

3226 Newcastle Dr, Dallas, TX 75220-1640

Executive Vice President: DAVID SUMNER,

K1ZZ

The purpose of QEX is to:

1) provide a medium for the exchange of ideas

and information among Amateur Radio

experimenters,

2) document advanced technical work in the

Amateur Radio field, and

3) support efforts to advance the state of the

Amateur Radio art.

All correspondence concerning QEX should be

addressed to the American Radio Relay League,

225 Main Street, Newington, CT 06111 USA.

Envelopes containing manuscripts and letters for

publication in QEX should be marked Editor, QEX.

Both theoretical and practical technical articles

are welcomed. Manuscripts should be submitted

on IBM or Mac format 3.5-inch diskette in word-

processor format, if possible. We can redraw any

figures as long as their content is clear. Photos

should be glossy, color or black-and-white prints

of at least the size they are to appear in QEX.

Further information for authors can be found on

the Web at www.arrl.org/qex/ or by e-mail to

qex@arrl.org .

Any opinions expressed in QEX are those of

the authors, not necessarily those of the Editor or

the League. While we strive to ensure all material

is technically correct, authors are expected to

defend their own assertions. Products mentioned

are included for your information only; no

endorsement is implied. Readers are cautioned to

verify the availability of products before sending

money to vendors.

2 May/June 2005

HF/VHF Power Meter

A PIC-based

Add an LCD display and a versatile PIC-Programmed

CPU to this popular log amp for 80 dB of

calibrated resolution on your bench.

By Roger Hayward, KA7EXM

Introduction

A variety of articles has been pre-

sented recently on simple, accurate,

power measurement using a logarith-

mic amplifier by Analog Devices. The

article by Wes Hayward, W7ZOI, and

Bob Larkin, W7PUA, 1 revealed the

AD8307 log amp, capable of measure-

ments from –80 dBm to +7 dBm and

from 1 to 500 MHz. Measurements can

be taken to levels up to nearly 100 W

with the use of an easy-to-build 40 dB

tap.

As is the case with most power

meters, an accurate calibration step is

required. This is performed by using

either a signal of known level, or by

comparing an unknown signal level

against another calibrated measure-

ment device.

Bob Kopski, K3NHI, presented an

article describing a way to provide the

home-experimenter with a method to

calibrate the meter. He translated the

output of the log amplifier into a 1 mV/

dB range, such that the measurements

could be displayed by a digital volt-

meter (DVM) module without the

need to convert measurement levels

through a lookup chart. 2 In a later

paper, he presented a simple RF sig-

nal source that can be calibrated with

an oscilloscope or RMS voltmeter. 3

This project begins with the same

log amplifier, and adds a PIC proces-

sor, LCD display and user control.

With a small on-board microprocessor,

significant additional features may be

employed:

• Calibration points are stored within

the FLASH memory of the PIC pro-

cessor.

• Power measurement levels are dis-

played on the screen in dBm, and,

optionally, in watts.

• When using a coupler, on-screen off-

set is included within the software.

• A high-accuracy differential mea-

surement mode allows the opera-

tor to measure insertion loss with

resolution better than 0.1 dB.

• Amplifier gain, return loss and even

VSWR can also be measured and

displayed with this differential

mode.

There are two goals in the presen-

tation of this article: First, if you

haven’t built a general-purpose RF

1 Notes appear on page 10.

13405 SW Juanita Pl

Beaverton, OR 97008

ka7exm@arrl.net

May/June 2005 3

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