HB_2003_2.pdf

HOMEBREWER

Magazine

Fall 2003

CONTENTS

A quarterly publication of

the American QRP Club

Features

Editor: George Heron, N2APB

n2apb@amqrp.org

3 Micro908 Antenna Analyzer II ........................ G. Heron, N2APB and J. Everhart, N2CX

11 RF Power Meter Cookbook II ......................... Joe Everhart, N2CX

16 Aaron's Clock, No Hands Required ................ Mark Spencer, WA8SME

19 Manhattan Project = Sidekick Rx + Tx ............ Jeff Grudin, AC6KW

24 Multi-band Coil for the PAC-12 Antenna ........ James Bennett, KA5DVS/6

26 Build the PicWx APRS Weather Station ......... Dave Ek, NK0E

30 Universal Power Supply ................................. Dave Ottenberg, WA2DJN

31 Melt Solder DDS Controller ............................ Steve Weber, KD1JV

35 Manhattan-Style Building Techniques - II ...... Cuck Adams, K7QO

Printer: Boston Form,

Cohasset, MA

The American QRP Club

Jim Cates, WA6GER

Chairman

email: wa6ger@amqrp.org

Doug Hendricks, KI6DS

President, Sales

email: ki6ds@amqrp.org

George Heron, N2APB

Sec’y, HB Editor, Webmaster

email: n2apb@amqrp.org

Joe Everhart, N2CX

Technical Manager

email: n2cx@amqrp.org

Paul Maciel, AK1P

Treasurer, Order Processing

email: ak1p@amqrp.org

Columns

38 TTAM: Test Topics And More ......................... Joe Everhart, N2CX

42 QRP Operating: “Well-Oiled Dummy Load” ..... Richard Fisher, KI6SN

45 Radio To Go: “Antennas To Go” ...................... James Bennett, KA5DVS/6

48 QRP in the Great Outdoors ............................... Ron Polityka, WB3AAL

50 Tuning Up: “Sniff, Sniff, Sniff” ......................... Richard Arland, K7SZ

53 QRP Contesting ................................................ Ken Newman, N2CQ

Odds ‘n Ends

2 From the Editor: “Bimodal” ................................ George Heron, N2APB

52 Four State News ................................................ Dave Bixler, W0CH

55 Kits from the NJQRP, NorCal, 4SQRP and AZsQRPions

56 Subscribing to HOMEBREWER

www.AmQRP.org

Online home of the AmQRP Club

containing ...

Advertisers

Elecraft ............................................................... Rear Cover

SuperAntennas .................................................. Inside Rear Cover

Red Hot Radio ................................................... Inside Front Cover

KangaUS ............................................................ Page 21

FAR Circuits ...................................................... Page 21

ElmerRadio ......................................................... Page 21

FingerDimple ...................................................... Page 44

News

Kits

Projects

Reference

QRP Forums

HB Extra!

QRP Contests

Links

... and more!

Our Cover ...

The Micro908 Antenna Analyzer is fea-

tured on our cover showing one of the many

uses for this project. Using the complex

impedance readings provided by the An-

tenna Analyzer, one can graphically repre-

sent the antenna’s characteristics on a Smith

Chart to determine corresponding lengths

of feedline needed for an optimized trans-

mitting system. Other computations can

be done manually to determine L/C com-

ponent values. Future software updates will

provide onboard computations for later

uploading and plotting data to the PC.

HOMEBREWER Online ...

HOMEBREWER Mag is online at:

www.amqrp.org/hbextra

Subscription details at:

www.amqrp.org/homebrewer

Subscriber status at:

www.amqrp.org/homebrewer/

substatus.html

Fall 2003

HOMEBREWER

From the Editor

“Bimodal”

I was walking around the vendor and project tables

at this year’s Pacificon QRP Forum in October, en-

tranced by the abundance of novel homebrew projects

and clever kits from the vendors, when the back-

ground of overlapping discussions started coming

into focus. Like moving out of a foggy mist into an

area of perfect clarity, I heard one QRPer after an-

other exclaiming the virtues of one project while

almost simultaneoulsy contrasting it against another.

Time and time again, as I moved among the many

tables bustling with shoulder-to-shoulder hams, I

heard these comparisons and contrasting commen-

tary about projects, operating practices and tech-

nologies. Although I didn’t realize it at the time, this

is when my theory of bimodal nature took birth.

elegant analog solutions. See, the condition usu-

ally swings both ways ... bimodal.

We here in HOMEBREWER Magazine, as with

other publications, try to cover the broad range

of our subscribers’ interests. However, unlike

other mags, we strongly target both “center fre-

quencies” of that bimodal distribution. We fea-

ture leading edge digital and microcontroller-based

projects for use in ham radio, yet we also have

basic and beginner RF projects that are based

solely in analog designs. We understand that some-

times an analog or digital sledgehammer can be

just the right solution for the grand design you

might be looking to create. As they say on one of

the cable channels, we present the facts -- simple

and complex, digital and analog, iambic A and iam-

bic B -- and let you make the decision.

Affilialtion with the AmQRP

We’re very pleased to welcome yet another

QRP club in under the AmQRP affiliate umbrella

-- the Arizona sQRPions .

Having a local QRP club join with the growing

ranks of other clubs across the country has a

great impact on its members, and also what the

organization is able to do. The group just needs

the desire to take on a little work along the way

with the guidance of experienced AmQRP lead-

ers and embrace the sponsorship for the benefit

of QRPers everywhere. AmQRP is only inter-

ested in fostering greater unity for QRPers and

proliferating the hobby, which ultimately brings

more solidarity and benefits to all in the com-

munity. We strongly believe in giving back ev-

erything we have to the hobby such that it can

grow and flourish — this is one major way of

doing that. We’ll expand on this “AmQRP

affiliation” concept a bit more in the next

issue.

Elmer 160 Course & the PIC-EL Kit

We are all very fortunate for the emergence of

a “PIC elmering” course being established this

fall by John McDonough, WB8RCR. Recogniz-

ing the latent desire held by many within the

QRP community, John has devised a structured,

online series of instructional lessons that lead one

through a better understanding of the PIC

microcontroller - both from a hardware as well as

software perspective. You can participate by fol-

lowing along in the lessons at www.amqrp.org/

elmer160.

The AmQRP felt so strongly about the impor-

tance of the Elmer 160 Course that it volunteered to

provide ample and timely hosting of lessons on the

main AmQRP website. Perhaps even more benefi-

cial, we activated a design team lead by Craig

Johnson, AA0ZZ, to develop a PIC-based “evalu-

ation card” specially suited for the course material.

The AmQRP kitting team is currently at work pre-

paring the pc board and kit for availability and soon

all students will be able to use it interactively with

the online lessons. See www.amqrp.org/elmer160/

board for full details, including those for ordering.

Enjoy the Issue!

As we head into this holiday season, let us relish

the bimodal nature that we each have as humans and

savor the the benfit it brings to our lives and to the

QRP hobby we all enjoy so much.

73 and Happy Holidays!

George Heron, N2APB

email: n2apb@amqrp.org

Yes

White

Analog

30 wpm

Black

Digital

12 wpm

Bimodal - a statistical distribution having two

peaks - is a concept that can be extended to our

normal QRP activities, contesting, homebrewing and

reading of the mail lists. It occurs to me that we all

have strong preferences and skillsets that guide our

everyday actions and we often reflect these biases

in the way we communicate. Having these biases is

a natural and good thing, as they often allow each of

us to contribute our own particular strengths and

gifts. Biases can, however, limit oneself and others

if they are conveyed with blinders that stiffle cre-

ativity and lower the bar of innovation.

For example, consider the homebrewer who is

looked down upon for varying the intensity of an

LED by using a PIC microcontroller to generate

pulse-width modulated waveform instead of using a

simple potentiometer. Using a PIC might be consid-

ered quite an overkill solution by someone who thinks

only in analog terms -- but think of the possible

extensions of this method, like being able to create

an additional pulsing indication, reversing the cur-

rent to drive a bi-color LED, etc. Conversely, the

“digital guy” might be trying to solve all his design

problems with a digital sledgehammer when he is

totally unawareness or closed-minded to simple and

PIC-EL Kit produced by the AmQRP for the

Elmer 160 Course. Has built-in programmer

for the 16F84A and circuits to provide basic

ham uses. Works with DDS Daughtercard.

Atlanticon 2004 QRP Forum

March 26-27 in Baltimore, Maryland

It’s now time to register for the annual QRP

event-of-the-year, happening for the 6th straight

year on the east coast. Over 160 hams from all

across America make their way to Baltimore in the

springtime to hear a superb set of presentations

from acknowledged QRP experts. Six exciting

speakers and a super fun-and-useful Atlanticon

Kit are all planned for this year’s event. See you

there!

Atlanticon 2004 QRP Forum

“Hosted by the NJQRP”

“Sponsored by the AmQRP”

• Holiday Inn Select in Timonium (410-252-7373)

• Friday evening social, club & vendor table

• World-class QRP presentations all day Saturday

• Hilarious QRP event & building contest Saturday evening

• Get bound proceedings and famous “Atlanticon Kit”

• Door prizes drawn all day long

• Major east coast hamfest same weekend & location

• Registration only $10

• See www.njqrp.org/atlanticon for more details

HOMEBREWER

Fall 2003

Joe Everhart, N2CX and George Heron, N2APB

Micro908

Antenna Analyzer II

Here’s a low cost, portable, microcontroller-based instrument that au-

tomatically determines SWR and reactance characteristics of an HF

antenna system. Advanced features of DDS frequency control, LCD

tuning display, PC data collection and plotting, numerous operating

modes and easy software upgradability make this design attractive for

homebrewers and antenna enthusiasts.

N2APB and N2CX have been complementary halves of a design team

working together in the NJQRP club over the past seven years – sort of like

the “Sonny & Cher” duo as applied to the world of QRP project design.

We’ve been fascinated with opportunities that digital computing technol-

ogy brings to the design of standard analog and RF radio equipment, mea-

surement fixtures and QRP accessories. Four years ago we created a proto-

type of an antenna analyzer – actually the predecessor of the one described

here – using relatively common components to create a very inexpensive

piece of test equipment.

Since then technology has advanced in the microcontroller world as well as

on the RF digital synthesis front. We’ve dusted off the design and aug-

mented the approach with some precision signal generation via a DDS

integrated circuit, used a ubiquitous LCD for the user display interface, and

incorporated a much more flexible and powerful microcontroller unit for the

computationally intense demands lying ahead.

In this paper we describe the design of an antenna analyzer that has two

tremendously exciting aspects to it. One is that it is based on some pretty

current technology – the AD9850 Direct Digital Synthesis chip from

Analog Devices and a quite flexible MCU ( microcontroller unit) from

Fall 2003

HOMEBREWER

Motorola called the HC908AB32. These two technologies give QRPers

considerable measurement and user interface power.

Secondly, the hardware platform on which the antenna analyzer software

runs is a multi-use, reconfigurable and field-programmable instrument called

the Micro908 . For the first time QRP homebrewers have available an

inexpensive-yet-powerful computing platform tailored to serve the spe-

cific needs in the ham shack. The concept and modules have been developed

over the last several years as chronicled in QRP Quarterly magazine as the

“Digital QRP Breadboard”, and now is available as a kit from the AmQRP

Club.

Both of these important aspects – the Antenna Analyzer software and the

Micro908 platform on which it runs – will be discussed in this paper. So as

Sonny & Cher said back then, “I’ve Got You Babe” and let’s dig into it all!

Overview

The Micro908 Antenna Analyzer is a small and inexpensive measurement

device designed to determine antenna performance across the amateur bands

through use of automatically collected SWR and complex impedance read-

ings. The figure below shows the block diagram of the Antenna Analyzer.

phones may also be used to listen to the tone.

The audio output feature is useful in yet another way for limited viewing

scenarios. The unit may be configured to audibly annunciate the displayed

measurement results via Morse code through the speaker or headphones.

The Micro908 Antenna Analyzer is designed to be field-usable and opera-

tor friendly. The handheld form factor lends itself to convenient operation

while away from the bench by means of pushbutton controls along the left

top side of the unit. The operator is able to easily select the various modes

and options with the left hand while making frequency and volume adjust-

ments with the right hand. Various interface connectors are placed along the

top side of the unit, including the RF connector, serial port connector, and

several other connectors (for aux, keyboard, paddles) that find use on the

Micro908 in other applications. The remaining interfacing connectors are

located along the right side panel of the unit – headphones, audio input (for

using the Micro908 as an audio filter), external power jack and the power

switch. The unit can be battery operated and the enclosure was selected to

hold eight AA cells.

Another exciting aspect to the Antenna Analyzer project concerns the

nature of the software used to control the microcontroller. There are a

growing number of computer-controller ham radio construction projects

being offered today by clubs, small companies and being described in the

literature. For the most part, however, they do not provide the source code

and design details that are of great interest by a growing number of

homebrewing amateurs capable of dealing with software modifications and

improvements. The Micro908 Antenna Analyzer project supplies fully

documented source code and design methodology for the software used to

control the device. The same is true for the software used for the compan-

ion remote control and display program in the PC.

The Micro908 Antenna Analyzer represents a unique, inexpensive and

fully functional design for the QRP homebrewer community. The Analyzer

is a project of great educational appeal - wideband transmitter design and

software control of its operation. The low-cost, straightforward and modu-

lar design places construction of the Analyzer well within the grasp of a

great many radio amateurs.

Antenna

system

under test

LCD

Fwd

Rev

Mode

Comm

Phones

Keyboard

Aux

12V

Vol

Busy

Reflectometer

A/D

Converter

HC908AB32

MCU

Band

Scan

Config

Spkr

Tune

Sleep

0-30 MHz

DDS

Batteries

DSP

User Interface

Figure 1 – Block Diagram of the Micro908 Antenna Analyzer

A very low power transmitter is swept across selected frequencies by a

microcontroller. The transmitter’s signal is delivered to the antenna system

through a reflectometer consisting of an absorptive SWR bridge and diode-

compensated buffer amplifiers. The data provided by the reflectometer are

digitized and used by the microcontroller to compute SWR and impedance

values. The microcontroller retains the frequency and corresponding re-

sults throughout the measurement period.

During this measurement period, the microcontroller rapidly displays the

individual frequency and SWR values on an LCD. When all data are col-

lected the microcontroller statically displays selected frequencies and the

associated SWR readings.

The frequency and SWR data may also be downloaded to a PC attached to

the Antenna Analyzer via a serial cable. A special software program for the

PC collects the data pairs and graphically represents the antenna perfor-

mance. This plot clearly shows the resonant frequencies of the antenna

system under test. The PC may also be used to remotely control the

Analyzer for manual selection of frequencies of interest.

Thus, with a press of a button the Antenna Analyzer is able to automati-

cally and quickly determine and display the frequency for which the an-

tenna system is best matched, along with the associated complex imped-

ance values at those frequencies.

Manual operation allows the user to control the band/frequency of opera-

tion while viewing the display of SWR results.

The Analyzer also functions as a simple frequency source in manual mode.

This signal may be used in troubleshooting various RF equipment.

The Micro908 Antenna Analyzer has a built-in speaker to allow use of the

unit when conditions do not permit easy viewing of the display. The device

may be configured to sound a tone whose pitch is varied based on the value

of the computed SWR. Thus the operator may manually tune for lowest

pitch and be assured that the specific frequency is the point of lowest

SWR. The feature may also be enabled for automatic scanning, although

one’s sanity will be stressed with this tone sounding all the time. Head-

Antenna Analyzer Features

• Automated, microcontrolled antenna network analyzer

• A powerful 8-bit microcontroller (NJQRP HC908 Daughtercard) con-

trols all aspects of the operation

• A low power DDS signal generator (the NJQRP DDS Daughtercard) is

swept across HF spectrum.

• Precise and self-calibrating reflectometer design measures forward and

reflected signals and impedance data

• Automatic scanning results displayed as frequencies of lowest SWR

and complex impedance

• Configurable frequency scanning limits and step sizes

• Manual control option displays SWR and complex impedance at se-

lected frequencies

• Audible tones provided assists in eyes-free tuning for minimum SWR

• Displayed results annunciated via Morse through internal speaker or

via headphones

• Serial port connects to PC for optional remote control and display/plot

of antenna performance

• Battery-operated for convenient field use, or can use external 12V for

bench operation

• Power-saving “sleep” feature powers down unit after presettable pe-

riod of inactivity

• Full hardware and software source material freely available via GNU

Public License

HOMEBREWER

Fall 2003

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