QEX 2006-09.pdf

ARRL

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The national association for

AMATEUR RADIO

ARRL’s

RF Amplifier

Classics

includes two-dozen projects

and articles from the pages of

QST

and

QEX

published

between 1980

and 2003.

There are amps

for HF, MF,

VHF and

microwave.

These are high quality works

from respected authors

such as Gary Breed, K9AY;

Jerry Pittenger, K8RA;

Bill Sabin, WØIYH;

Al Ward, W5LUA;

Dave Meacham,

W6EMD and others.

Use this book and…

■ Shorten your discovery work

■ Find practical designs and

construction details for

classic tube and solid-state

amplifiers at power levels

from 5 W to 1.5 kW

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■ Produce loud and clean

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Quick access to utilities,

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MORE EQUIPMENT,

ACCESSORIES AND

ANTENNAS FOR

LOW POWER

RADIO OPERATING!

magazine

■ Contesting software , including

N1MM Logger

■ CW Decoder

■ WinDRM digital voice software

■ HF digital software for PSK31,

MFSK16, MT63, RTTY and more

■ WSJT software for meteor scatter

and moonbounce

and more!

You’ll also find programs for APRS ,

Winlink 2000 , packet radio and

satellite tracking . Plus, handy

software tools for calculating

transmission line loss, creating

custom DSP audio filters, and more.

Bonus files include ARRL

screensavers, audio samples, video

files, and PowerPoint presentations.

Minimum System Requirements: A 400 MHz

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Windows ® XP or Windows 2000. A sound card is

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sound-card-based digital communication software.

Includes the free Adobe ® Reader ® and Microsoft ®

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The ARRL

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Build a tiny station that you can

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QEX

magazines. Here are more

projects and articles for low

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■ Construction practices

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QEX 9/2006

Book excerpts and a selection

of articles from the pages of

QST

published in the

1990s, More QRP Power is an

anthology of articles from recent

issues of

ARRL’s

The national association for

AMATEUR RADIO

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 238

About the Cover

Bertram Zauhar, VE2ZAZ, describes the

construction and operation of a high-

accuracy frequency standard based on

a GPS receiver board. The cover

photos show his project connected to

an HP frequency counter, along

with a view inside the

project box.

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

860-594-0203 direct

860-594-0200 ARRL

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Circulation Department

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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:

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

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Elsewhere by Airmail: ARRL member $59,

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Members are asked to include their membership

control number or a label from their QST when

applying.

Features

3 Get 1.5 kW from a New RF MOSFET: A Legal Limit HF

Linear, Tokyo Style

By Toshiaki Ohsawa, JE1BLI, and Nobuki Wakabayashi, JA1DJW

14 A Simplified GPS-Derived Frequency Standard

By Bertrand Zauhar, VE2ZAZ

22 Installing Vertically Polarized Yagis in the T-Mount

Configuration

By Rick Littlefield, K1BQT

25 An IF Signal Generator

By John Pivnichny, N2DCH

28 Magnetic Coupling in Transmission Lines and

Transformers

By Gerrit Barrere, KJ7KV

37 Easy Microwave Filters Using Waveguides and Cavities

By Paolo Antoniazzi, IW2ACD, and Marco Arecco, IK2WAQ

43 Q Calculations of L-C Circuits and Transmission Lines:

A Unified Approach

By Jacques Audet, VE2AZX

52 Some Thoughts About the Quality Factor of a Coil

By Pierre Desjardins, VE2PID

54 What’s Your CQ? (Curiosity Quotient)

By Eric P. Nichols, KL7AJ

Columns

54 Upcoming Conferences

55 Antenna Options

By L. B. Cebik, W4RNL

62 Letters

63 Next Issue in QEX

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Sep/Oct 2006 QEX Advertising Index

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Tucson Amateur Packet Radio Corp.: 21,

Sep/Oct 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:

PD7720. AT&T was

right there, too, with their DSP1. Both were

presented at the IEEE International Solid-

State Circuits Conference in 1980. Texas

Instruments introduced the TMS32010 in

1983, which proved to be a huge success.

Motorola entered the market with their

MC56000 at around that time, as well. Ana-

log-to-digital converter (ADC) technology

was still in its infancy, though, by today’s

standards.

A landmark article appeared in QST in

1984 describing DSP and what was com-

ing. 1 It’s an excellent tutorial on the basics

and it even makes some predictions that

turned out to be quite accurate.

Complementary metal-oxide semiconduc-

tors (CMOS) were devised by Frank

Wanlass at Fairchild in 1963; however, it

wasn’t until the early 1980s that the 4000

series of logic chips and CMOS micropro-

cessors became popular. Low power drain

— hence low digital circuit noise — made

them practical in radio designs. CMOS

phase-locked loop (PLL) chips, including

the 4046, multiplied frequency synthesis

applications. Led by Signetics and

Motorola, advancement of PLLs on a chip

proceeded rapidly.

Although hams had documented their

experimentation with frequency synthesis

since the 1960s, articles that included PLLs

and microprocessor control didn’t appear in

amateur publications until the 1980s. In

1988, a noted article appeared in ham

radio about direct digital synthesis (DDS). 2

It sent designers scurrying to explore

the technique, although DDS and PLL

had already been combined at Rockwell

Collins by the late 1970s. Qualcomm,

Harris and others introduced integrated

DDS chips that made the technique practi-

cal if not economical at first.

AMTOR, and then PACTOR, arrived in

the 1980s, forcing manufacturers to pay at-

tention to turn-around times between trans-

mit and receive. Those developments also

gave designers impetus to revisit their auto-

matic gain control (AGC) and automatic

level control (ALC) circuits for transient

response.

The 1990s brought steady improvements

in synthesizer phase noise, receiver dy-

namic ranges and frequency stability. DDS-

driven PLLs began to win most synthesizer

design decisions. Computer control became

a standard feature on most transceivers.

Units that exclusively used computer con-

trol, without manual front-panel controls,

appeared. Some thought that would be the

model for all future designs but it turned out

not to be the case.

Near the turn of the millenium, we saw a

split in design philosophies, with the advent

of inexpensive, high-dynamic-range ADCs,

the development of which was initially

driven by digital audio and video applica-

tions. On the one hand, low-IF DSP rigs

became the norm in high-performance de-

signs. On the other hand, increasing ADC

speeds, resolutions and dynamic ranges

eventually made practical today’s direct-

conversion software radios.

In virtually every case, design improve-

ments were spurred by demands for either

better performance or lower cost, or both.

Both goals have been achieved in both

branches but there are still major gaps be-

tween them. Transmitter intermodulation

distortion stands out as one area in which

not much progress has been made.

All told, it’s been an amazing journey.

Some have asked, “What’s the next big

breakthrough?” To answer that question is

to first look at the definition of break-

through: “An act of breaking through an

obstacle or barrier....” 3 So what’s the next

big obstacle? Is it band crowding or inter-

ference? Cost of equipment? The survival of

our Service? What do you think?

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 R. Olsen, N6NR, “Digital Signal Process-

ing For The Experimenter,” QST, Nov

1984, pp 22-27; available on the Web at

www.arrl.org/tis/info/pdf/79135.pdf

2 R. Zavrel, Jr, W7SX, “A Direct Digital Syn-

thesis VFO,” HAM RADIO, Sep 1988, pp

10-17.

3 L. Brown, ed-in-chief, The Shorter Oxford

English Dictionary, 5th ed, Oxford Uni-

versity Press, 2002.

2 Sep/Oct 2006

A Brief Look Back

Over the span of QEX ’s existence, sev-

eral design revolutions have devolved upon

the communications world. Looking back,

it’s difficult to see how we survived with-

out them.

In 1981, the IBM PC had just been intro-

duced. Almost nobody knew who Bill

Gates was. Highly integrated synthesizer

chips were just coming onto the market.

Printed circuit boards were manufactured in

much the same way as they are now but we

created artwork by manually laying crepe

tape on Mylar sheets. Capable microproces-

sors were available for embedded designs

but their widespread use in transceivers

would wait several years. Digital signal pro-

cessing (DSP) was impractical except in

high-end applications, although the theory

of it was quite advanced.

The 1980s saw vast improvements in all

those areas. NEC introduced one of the first

complete DSPs: the

Get 1.5 kW from a New RF

MOSFET: A Legal Limit HF

Linear, Tokyo Style

Legal limit output power on all amateur MF and HF bands from

a pair of RF power MOSFETs in push-pull configuration.

Toshiaki Ohsawa, JE1BLI, and Nobuki Wakabayashi, JA1DJW

since Motorola introduced their

T-MOS RF power FETs. Helge

Granberg, K7ES, described a 1.5 kW

amplifier using those transistors for QEX

readers. 1 Since then, devices equivalent to the

Motorola MRF150 as well as other new

devices have been developed by several

semiconductor manufacturers. Among them

there is one interesting device called the

ARF1500 developed by Advanced Power

Technology, Inc of Bend, Oregon, USA

( www.advancedpower.com ). This device has

a 500 V drain-to-source breakdown voltage

rating and 1500 W of power dissipation

capability. After looking at this specification,

we thought a full-legal-limit HF power

amplifier would be possible without any

power combining. After many experiments,

we have succeeded in designing a compact

push-pull broadband amplifier with 1.5 kW

output over 1.8 to 30 MHz.

The ARF1500 package has a unique

construction, very different from

conventional high power RF power

transistors. Instead of the conventional

ceramic package and copper-tungsten

flange, a large rectangular plastic molded

cover and a special base material are used.

The base material is berylia (beryllium oxide

— BeO) ceramic. It is a very good electrical

insulator with very low thermal resistance,

between that of copper and aluminum. It

conducts the dissipated heat away from the

transistor into the heat sink on which it is

mounted. BeO is lethal if inhaled so you

must never scratch the bottom surface.

Some excellent features of the ARF1500

are as follows:

•

(safe operating area) can be expected. This,

along with the high V dd rating, makes it much

more rugged than conventional power

devices.

In addition, the internal structure is

optimized for stable RF and dc performance.

The mounting surface area is much larger

than conventional transistors and this greatly

facilitates heat sinking.

On the other hand, some tough points in

the application are:

•

Low input impedance : With 5000 pF

of input capacitance, the gate input

impedance becomes so low that matching it

over a wide frequency bandwidth is much

more difficult than with lower power

devices.

•

High power : It has a high enough

power-handling capability that a single push-

pull amplifier can build a practical amplifier

with one kilowatt minimum output.

•

Peripheral components selection : The

higher RF current will cause more heat

generation due to the I 2 R losses in the passive

components used around the ARF1500.

Capacitor dielectric loss, magnetic

saturation and heat dissipation of ferrite

cores, etcetera must all be carefully

considered.

•

High voltage : With a breakdown

voltage rating of 500 V, the operating voltage

can be at least two times higher than

conventional RF devices. At the higher

voltage, the drain impedance is much higher

and the performance is less subject to dc

power supply regulation, greatly simplifying

the design of the power supply.

•

Heat-sink design : Due to the high

dissipated power in the devices, the heat sink

and cooling system must be very efficient

to keep the junction temperature of the

ARF1500 below a reasonable limit.

We set a design goal for a single stage

push-pull pair of ARF1500s as follows:

Output power: 1.5 kW.

Frequency range: 1.8 ~ 30 MHz (amateur

High current : The maximum drain

current specification is 60 A, a wide SOA

1 Notes appear on page 13.

Room 906, 2 - 1 Sakae 5-chome

Asaka, Saitama 351-0012

Japan

rfpro2@thp.co.jp

5 - 27 Higashi 1-Chome

Niiza, Saitama 352-0002

Japan

marketg@thp.co.jp

Sep/Oct 2006 3

ohsawa.pmd

08/02/2006, 2:52 PM

M ore than two decades have passed

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