QEX 2006-07.pdf

ARRL

225 Main Street

Newington, CT USA 06111-1494

The national association for

AMATEUR RADIO

ARRL Periodicals

on CD-ROM are

fully-searchable collections of popular

ARRL journals. Every word and photo

published throughout the year is

included!

SEARCH the full text of every article by entering titles,

call signs, names — almost any word. SEE every word,

photo (including color images), drawing and table in

technical and general-interest features, columns and

product reviews, plus all advertisements. PRINT what

you see, or copy it into other applications.

System Requirements:

Microsoft Windows ™ . 1999, 2000, 2001, 2002, 2003, 2004 and 2005 editions support

Windows and Macintosh systems, using the industry standard Adobe Acrobat Reader ®

(included).

Communications Quarterly CD-ROM

This CD-ROM collection covers volumes of Communications Quarterly published

from 1990-1999. Gain access to advanced technical topics in articles which cover

transmitter, receiver and transceiver projects, theory, antennas, troubleshooting and

much more. High quality black-and-white page scans can be read on your computer

screen or printed. Quickly search for articles by title and author, select specific year

and issue, and browse individual articles and columns.

Requires Microsoft Windows ™ .

QST View

Every page of QST— all the ads, articles, columns and covers— has

been scanned as a black-and-white image that can be viewed or printed.

BONUS! Latest, enhanced viewer— AView —included with any

QST View purchase. AView is compatible with all sets of QST View .

ARRL CD-ROM Collections

QST View CD-ROM

#7008 Years 1915-29 ..................... $39.95

#6710 Years 1930-39 ..................... $39.95

#6648 Years 1940-49 ..................... $39.95

#6435 Years 1950-59 ..................... $39.95

#6443 Years 1960-64 ..................... $39.95

#6451 Years 1965-69 ..................... $39.95

#5781 Years 1970-74 ..................... $39.95

#5773 Years 1975-79 ..................... $39.95

#5765 Years 1980-84 ..................... $39.95

#5757 Years 1985-89 ..................... $39.95

#5749 Years 1990-94 ..................... $39.95

#8497 Years 1995-99 ..................... $39.95

#9418 Years 2000-2004 ................. $39.95

#QSTV (all 13 sets) ... Only $399 (Save $120)

ARRL Periodicals CD -ROM

(includes QST, QEX, NCJ)

#9574 Year 2005 ............................ $19.95

#9396 Year 2004 ............................ $19.95

#9124 Year 2003 ............................ $19.95

#8802 Year 2002 ............................ $19.95

#8632 Year 2001 ............................ $19.95

#8209 Year 2000 ............................ $19.95

#7881 Year 1999 ............................ $19.95

#7377 Year 1998 ............................ $19.95

#6729 Year 1997 ............................ $19.95

#6109 Year 1996 ............................ $19.95

#5579 Year 1995 ............................ $19.95

Communications Quarterly CD -ROM

#8780 (1990-1999) ........................ $39.95

Ham Radio Magazine CD-ROM*

#8381 Years 1968-76 ..................... $59.95

#8403 Years 1977-83 ..................... $59.95

#8411 Years 1984- 90 ..................... $59.95

#HRCD (all three sets) ................. $149.85

QEX Collection CD-ROM

#7660 (1981-1998) ........................ $39.95

NCJ Collection CD-ROM

#7733 (1973-1998) ........................ $39.95

www.arrl.org/shop

1-888-277-5289 (US)

Shipping & Handling charges apply : US orders add $6 for one CD, plus $2 for each additional CD ($12 max.).

International orders add $5.00 to US rate ($17.00 max.). Or, contact ARRL to locate a dealer. Sales Tax is required

for orders shipped to CA, CT, VA, and Canada.

QEX 7/2006

NEW EDITION!

NEW!

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 237

About the Cover

This NASA synthetic aperture radar

antenna was modeled using the

methods presented in “Adventures in

Curve-Fitting.” The graphical user

interface display is the

software that implements a

nonlinear tuning algorithm.

Harold Kramer, WJ1B

Publisher

Doug Smith, KF6DX

Editor

Larry Wolfgang, WR1B

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

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 I-V Curve Tracing With A PC

By Dr George R. Steber, WB9LVI

10 Transverter RF/IF Switching Using GaAs MMICs

By Steve Kavanagh, VE3SMA

13 Octave for System Modeling

By Maynard Wright, W6PAP

19 An Innovative 2-kW Linear Tube Amplifier

By Saulo Quaggio, PY2KO

30 Adventures in Curve-Fitting

By Dr H. Paul Shuch, N6TX

37 Effective Directivity for Shortwave Reception by DSP

By Jan Simons, PAØSIM

46 Practical RF Soil Testing

By Eric von Valtier, K8LV

50 Crystals

By Andrzej Przedpelski, KCØCWK

Columns

53 Antenna Options

By L. B. Cebik, W4RNL

61 Letters

63 Out of the Box

64 Next Issue in QEX

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.

Jul/Aug 2006 QEX Advertising Index

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 )

American Radio Relay League: Cov II,

12, 52, Cov III, Cov IV

ARA West: 64

Atomic Time: 36

Down East Microwave, Inc.: 64

Elkins Marine Training International: 64

jwm Engineering: 29

National RF: 64

Nemal Electronics International, Inc.: 60

RF Parts: 49

Teri Software: 60

Timewave Technology, Inc: 45

Tucson Amateur Packet Radio Corp.: 63

Jul/Aug 2006 1

THE AMERICAN RADIO

RELAY LEAGUE

Empirical Outlook

Doug Smith, KF6DX

kf6dx@arrl.org

The American Radio Relay League, Inc, is a

noncommercial association of radio amateurs,

organized for the promotion of interest in Amateur

Radio communication and experimentation, for the

establishment of networks to provide communica-

tions in the event of disasters or other

emergencies, for the advancement of the 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 organization

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 three 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:

Models and Measurements:

Mandate for Change

Three years ago, a small group of engi-

neers and scientists who are also avid hams

united to improve the state of transceiver

testing in Amateur Radio. Articles you con-

tributed here and elsewhere formed some of

the background for their subsequent dis-

cussions. The group identified significant

discrepancies in published test data and

methods, including those related to third-

order intercept point, composite noise and

blocking dynamic range. Also identified

were several areas where tests were notably

lacking or missing. The group has begun to

document its findings and suggestions. 1, 2, 3

That series shall continue here, with some

of the following points in focus.

For receivers, chief among the enemies of

performance from within are noise and

“birdies.” We have articles coming that will

deal specifically with those issues, and

more.

The main issue with receiver noise test-

ing is bandwidth dependence. Because a

receiver’s noise floor power sets one end of

dynamic-range measurements, it would be

nice if it were expressed in bandwidth-in-

dependent terms. The ARRL Handbook

mentions normalizing noise to a 1-Hz band-

width, as is done for phase-noise data. Al-

ternatively, a noise figure in dB could be

stated. Measurements that don’t measure

noise figure directly can be converted to that

basis when the noise power and bandwidth

of the measurement are accurately known.

Birdies are signals appearing in or near a

receiver’s passband that are caused by the

fundamentals or harmonics of internal os-

cillators or the unwanted mixing products of

them. They’re largely ignored in formal re-

ceiver testing now, but they’re as important

to potential buyers as other parameters.

They need to be predicted and examined.

Other enemies from within that need

more regular attention are things like fre-

quency accuracy and stability, leakage of

local oscillators and other signals to the an-

tenna, automatic level control and its effect

on transient occupied bandwidth, Part 15

and CE compliance, and reliability, service-

ability and warranty of equipment. All

those things are of interest to buyers and

users alike.

Enemies to performance from without

depend on conditions outside the unit under

test. The bandwidth dependence of receiver

dynamic-range testing should be removed.

Every test must measure what it’s supposed

to measure. Receiver spurious responses

other than IMD2 and IMD3 are not gener-

ally searched but they need to be explored.

That’s especially important for rigs using

direct digital synthesis or digital direct con-

version schemes. Receivers with analog-to-

digital converters close to the antenna don’t

always behave according to traditional mod-

els. Yes, they exhibit second-, third- and

higher-order distortions, but not as tradi-

tional units do. It remains to be seen what

other software-radio-related limitations

must be defined and measured. That will be

the subject of future articles here.

Some performance measurements over

ranges of supply voltages, temperature and

vibration should be standard. Prospective

buyers and users need to know what protec-

tion circuits a rig employs: VSWR power

cutback, antenna tuner range and efficiency,

reverse polarity and overvoltage protection

at the power input, lightning and static dis-

charge protection, and so forth.

Then there are certain ergonomic issues

for which it’s difficult to specify and design

tests; but in this microprocessor-controlled

age, it is possible to test control systems.

One test is the famous “dead-man test,”

wherein you engage all the controls on a rig

in random combinations to try to make the

unit crash. The processed audio quality of

transmitters and receivers, especially when

special digital techniques like noise reduc-

tion are being used, is difficult to report

objectively but we do have methods of con-

verting subjective evaluations.

Measurements must be grounded in es-

tablished scientific principles. They must be

traceable to standards of known precision.

Uncertainties must be declared for all mea-

surements. When systematic measurement

errors are discovered, previously published

data must be corrected.

In short, changes and additions to exist-

ing test methods, along with corrections to

already-published data, are mandated and as

part of our stated mission at QEX , we’ll be

here to document them. The ARRL, for one,

is taking steps in the right directions. See

recent QST Product Review columns for

details

— 73, Doug Smith, KF6DX, kf6dx@arrl.org

ARRL, 225 Main Street, Newington, CT 06111 USA.

Telephone: 860-594-0200

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

Officers

President: JOEL HARRISON, W5ZN

528 Miller Rd, Judsonia, AR 72081

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 experiment-

ers,

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 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 or high-resolution digital images (300 dots per

inch or higher at the printed size). 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.

Notes

1 U. Rohde, N1UL, “Receiver Measure-

ments, How to Evaluate Receivers,”

Jul/Aug 2005 QEX, pp 3–11.

2 D. Smith, KF6DX, “Tech Notes: Quantify-

ing Measurement Uncertainty,” Jan/ Feb

2006 QEX, pp 54–56.

3 L. Åsbrink, SM5BSZ, “Blocking Dynamic

Range in Receivers,” Mar/Apr 2006 QEX,

pp 35–39.

2 Jul/Aug 2006

I-V Curve Tracing With A PC

Design of an Inexpensive PC Sound Card Curve Tracer

Dr George R. Steber, WB9LVI

to learn more about electronic

components. By curve tracing, we

mean making a graph of current versus

voltage (an I-V curve) to display the basic

characteristic of the electronic device. The

I-V curves of diodes, LEDs, transistors

and other devices are very helpful in

understanding their nonlinear operation. Such

curves are useful in establishing circuit

models as well as determining bias points,

load lines and limitations of the devices. For

many, curve tracing seems to be a lost art and

many experimenters rely only on curves

supplied by the device manufacturer.

Unfortunately, the manufacturers’ I-V

curves are not always handy or the devices

may not be documented at all. Of course,

there are commercial curve tracers that will

do the job but they are outside the realm of

most experimenters. In this article I will

attempt to remedy that situation and describe

for you an economical way of obtaining the

I-V curves of two and three terminal devices

using a PC, a simple circuit, a Windows -

compatible sound card and a bit of software.

To my knowledge, no one has previously

used the sound card inputs of the PC for

curve tracing without resorting to fancy

modulation schemes. There is good reason

for this as most sound card inputs are ac

coupled. That is, there is a capacitor in series

with each input that effectively removes the

dc value of the signal. When tracing a

nonlinear device, like a diode, the actual dc

value must be used or accuracy will suffer.

While the PC sound card has a nice pair of

16 bit analog-to-digital (A/D) converters of

relatively good accuracy they would be of

little value unless this coupling problem was

solved. A novel and completely new method

that retains the dc value when using a sound

card was developed by the author and

disclosed in a recent article. 1 One outstand-

ing feature of the procedure is that it can be

implemented without modifying the sound

card or even opening up the PC case.

For this project I have designed a new

circuit that is much simpler than the one

described previously (see Note 1) and have

also written new software to make it easier

to use. An abbreviated article describing

construction and operation of this new curve

tracer appears in the July 2006 issue of QST . 2

Presented here are the technical details

behind this unusual system, dubbed Curve

Tracer II. In case you don’t have the QST

article handy I will also present some

material on installation and operation of the

curve tracer as well as theoretical details and

additional application material for tracing

transistors and integrated circuits. It’s a

project that should appeal to almost anyone

involved in electronics.

This project requires a PC running the

Windows operating system. You can use one

of the newer 3 GHz PCs or dust off your old

200 MHz PC. Of course, there are no

guarantees that this project will work with

your system. But it has been tested with a

200 MHz Pentium Pro, a 500 MHz Pentium

III, and a 1.1 GHz AMD Athlon processor

running Windows 98SE and Windows XP with

Sound Blaster (SB) Live! , Value Edition .

So, if you have a Pentium or AMD PC

with a Windows -compatible sound card, you

probably have the basis for a very good

Windows -driven curve tracer. All you need

to do is build the simple circuit described,

connect it to your computer sound card and

run the program. You will be able to

accurately plot the I-V characteristics of

many two and three terminal devices such

as resistors, diodes, Zener diodes, LEDs,

transistors, integrated circuits and others.

Data is captured via the sound card stereo

input, processed and plotted on the screen.

The circuitry is very low cost (less than

$2.00) and uses readily available parts. You

can build the circuit on a solderless

breadboard like I did, or design a circuit

board for it. In any case you will need a

digital voltmeter (DVM) for calibration

purposes. To get started it will be helpful to

review some concepts of curve tracing.

DC and AC Curve Tracing

Curve tracing with dc signal levels is

simple in principle, and requires an adjust-

able dc power supply, ammeter, voltmeter and

current limiting resistor, R, as shown in

Figure 1A. In this case only a positive volt-

age is shown, but both polarities are often

used for tracing. One adjusts the supply volt-

age while monitoring the meters and writes

down the meter readings as a table of I and

V values. From the table, data points can be

plotted to obtain a graph, like the one shown

at Figure 1B. While this works well, it has

several drawbacks. One has to manually ad-

just the voltage at reasonable intervals, read

and write down the data, and finally plot it.

You also have to switch power leads if you

want to plot negative voltages. If more than

a few devices need characterization, an au-

tomatic method is preferable. Clearly, if you

have a bag of diodes, LEDs or Zeners that

you just bought at a hamfest and want to test

them, this is not the way to do it.

1 Notes appear on page 9.

9957 N River Road

Mequon, WI 53092

steber@execpc.com

Jul/Aug 2006 3

C urve tracing is an interesting way

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: