QEX_2006_01_02.pdf

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Forum for Communications Experimenters

January/ February 2006

Issue No. 234

N8LP’s Versatile Meter accurately

measures Power, SWR and Return Loss

from 0.5-54 MHz and 2-2000 W.

ARRL

225 Main Street

Newington, CT USA 06111-1494

The national association for

AMATEUR RADIO

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QEX 1/2006

AMATEUR RADIO

INCLUDING:

About the Cover

Not your average, run-of-the-mill

wattmeter. Read all about it,

beginning on page 3.

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 234

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

Devon Neal

Technical Illustrator

Joe Shea

Production Assistant

Advertising Information Contact:

Janet L. Rocco, W1JLR

Business Services 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

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 The LP-100 Wattmeter

By Larry Phipps, N8LP

14 PSpice for the Masses

By Randy Evans, KJ6PO

22 Quantifying SETI

By Dr H. Paul Shuch, N6TX

31 The Harmanized R4C–A High-Performance Analog HF

Receiver

By Phil Harman, VK6APH, and Steve Ireland, VK6VZ

41 8877 “Lite”–A 50-MHz 20-Pound Travel Amplifier

By Dick Hanson, K5AND

Columns

21 Upcoming Conferences

47 Antenna Options

By L. B. Cebik W4RNL

54 Tech Notes

By Doug Smith, KF6DX

57 Letters

61 Next Issue in QEX

Jan/Feb 2006 QEX Advertising Index

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.

American Radio Relay League: Cov II,

62 , 64, Cov III, Cov IV

ARA West: 63

Atomic Time: 56

Down East Microwave, Inc.: 21

Elkins Marine Training International: 63

Expanded Spectrum Systems: 63

jwm Engineering: 13

Mackay Communications: 40

National RF: 64

Nemal Electronics International, Inc.: 64

Noble Publishing Corp.: 64

RF Parts: 63

Teri Software: 13

Tucson Amateur Packet Radio Corp.: 62

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 )

Jan/Feb 2006 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.

Know Your Readers

The original writer is not he who

refrains from imitating others, but he

who can be imitated by none. [François-

René Chateaubriand (1768-1848) in

Le Génie du Christianisme, 1802 ]

As a technical writer, you strive to ex-

plain some science or technology to read-

ers who know less about it than you do,

in a way they can understand. That defi-

nition might seem obvious, but it’s worth

keeping in mind every day, every hour

you write. Quite often, you must convey

rather complex information in simple

terms. At other times, more elaborate ex-

planations become necessary. Knowing

when they are necessary is crucial to

good technical writing. The business of

straightforwardly explaining technical

concepts involves trade-offs—some dis-

tinct and some indistinct—among clar-

ity, readability and detail. It’s tempting

to state that those trade-offs need never

occur; at the keyboard, though, you soon

discover it’s not easy every time.

Part of what readers understand

about your topic before they start read-

ing is unknown to you, but some prereq-

uisite knowledge is assumed. If you were

writing an installation and operation

manual for a VCR, for example, you’d

assume that readers know that the thing

puts motion pictures and sound on a tele-

vision receiver. You might also assume

that readers expect to connect it to the

receiver and to a source of power, al-

though not precisely how to do that.

What you cannot assume is their aware-

ness that bad mistakes during installa-

tion can electrocute them .

Given that you know more about your

topic than do your readers, you’re a

teacher. Some pupils may wonder why a

video cable must be shielded and some

may already know why. A good teacher

tries to impart everything necessary for

basic understanding to a class and also

accommodates more advanced students

by giving some insight into what lies be-

yond the basics.

In This Issue

Larry Phipps, N8LP, describes his high-

performance digital wattmeter. Larry gives

a thorough presentation of operating prin-

ciples and performance, from the directional

coupler and detectors to the display.

Randy Evans, KJ6PO, enlightens us

about a PSpice program that you can get

without money. Investing time to learn

how to use it may pay substantial divi-

dends. It’s nice to know what you’re

doing at every point in the design pro-

cess. At our invitation, H. Paul Shuch,

N6TX, put some words together about

“Quantifying SETI.” Paul discusses cer-

tain technical issues related to the goal

of communicating with extraterrestrial

intelligence.

Our friends from “down under,” Phil

Harman, VK6APH, and Steve Ireland,

VK6VZ, show us what they’ve done with the

venerable Drake R4C receiver to

“harmanize” it. Check it out.

Dick Hanson, K5AND, produces an-

other great amplifier: the “8877 Lite.” At

20 pounds, it will let you stay QRO while

on the go.

In Antenna Options , Contributing

Editor L.B. Cebik, W4RNL, addresses a

critical antenna parameter: gain. In

Tech Notes , I explain the universally

accepted way of combining measure-

ment uncertainties. The ARRL is con-

templating its use to declare the

accuracy of product-review test results.

Happy new year.— 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

Chief Executive Officer: 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.

Managing Editor Robert J. Schetgen, KU7G, SK

For eight years, Bob lived at the center of the work storm here at QEX . We, his

mourning friends and colleagues, dedicate this issue to him, the brilliant editor who

contributed so vastly to our success.

A life member, Bob came to ARRL in 1983 as Technical Information Specialist. His

other titles included Hints & Kinks Editor, Senior Assistant Technical Editor and

ARRL Handbook Editor. He edited many other popular ARRL books, such as QRP

Classics , Hints & Kinks , Vertical Antenna Classics , and Packet: Speed, More Speed and

Applications .

Bob became a ham in 1963. He grew up in Southern California, attending Cal Poly

University at Pomona. He always greeted you with a smile and a friendly word, even

during his illness. He knew his job and performed it well. Bob is survived by his wife

Ellen, a daughter and a sister, and a legacy and influence in journalism that will live

on. May God bless him.

2 Jan/Feb 2006

The LP-100 Wattmeter

A high-performance, microprocessor-controlled digital

SWR/wattmeter with wide dynamic range

By Larry Phipps, N8LP

ongoing design exercise. The

main meter chassis has re-

mained fairly unchanged through sev-

eral iterations of the project, but the

directional coupler has undergone

some radical changes, with several

new designs still undergoing testing

and modification. I will describe the

first iteration of the project fully in this

article. At the conclusion of the article,

I will discuss some of the changes to

the coupler, and will refer the reader

to my Web site ( www.telepostinc.

com ) for the latest details.

Here are the basic specifications/

features of the meter…

• Coverage from 0.5 to 54 MHz for

rated specs with the specified cou-

pler designs

• Auto-ranging scales covering 0-2,

20, 200 and 2000 W

• Modular design to allow for differ-

ent couplers

• Scale for dBm measurements,

~ –15.0 dBm to +63.0 dBm in

0.1 dB steps

• Power display resolution of 0.01,

0.1 or 1 W depending on scale.

• Power accuracy better than ±.5 dB

to <10 mW, typically 5% after cali-

bration

• Displays actual power delivered to

the load (Fwd minus Ref)

• SWR display resolution of 0.01

• Overall SWR accuracy typically

within ±0.1 of actual down to 100

• Return Loss (RL) display of 0 to

49.9 dB

• State-of-the-art PLED display with

screen saver

• Fast responding logarithmic bar-

graphs for power, SWR and RL

• Peak-hold numerical power readout

with fast and slow time constants

• SWR Alarm system with set points

for 1.5, 2.0, 2.5 and 3.0

• Separate calibration screen

• Serial port for external software

control

49100 Pine Hill Dr

Plymouth, MI 48170

larry@telepostinc.com

Jan/Feb 2004 3

T he LP-100 project is really an

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