QEX 2002-05

68 Pages·2017·5.21 MB·English

$5
INCLUDING:
Forum for Communications Experimenters
May/June 2002
KJ6PO’s 10-MHz Frequency Standard
ARRLThe national association for
AMATEUR RADIO
225 Main Street
Newington, CT USA 06111-1494

About the Cover
KJ6PO’s wiring board
INCLUDING: floats above the chassis
that normally contains
QEX (ISSN: 0886-8093) is published bimonthly it. The article begins
in January, March, May, July, September, and
November by the American Radio Relay League, on p 13.
225 Main Street, Newington CT 06111-1494.
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nonmembers $36. Other rates are listed below.
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POSTMASTER: Send address changes to:
QEX, 225 Main St, Newington, CT 06111-1494
Issue No 212
Mark J. Wilson, K1RO Features
Publisher
Doug Smith, KF6DX
Editor
Robert Schetgen, KU7G 3 An Advanced VHF Wattmeter
Managing Editor
By Bob Kopski, K3NHI
Lori Weinberg, KB1EIB
Assistant Editor
Peter Bertini, K1ZJH 9 A Quiet Antenna Tuner
Zack Lau, W1VT
Ray Mack, WD5IFS
By Tony Lymer, GM0DHD
Contributing Editors
Production Department
Steve Ford, WB8IMY 13 A Laboratory-Grade 10-MHz Frequency Standard
Publications Manager
Michelle Bloom, WB1ENT By Randy Evans, KJ6PO
Production Supervisor
Sue Fagan
Graphic Design Supervisor 22 On Measuring R
s
David Pingree, N1NAS
Technical Illustrator By Warren B. Bruene, W5OLY
Joe Shea
Production Assistant 26 A Homebrew Regenerative Superheterodyne Receiver
Advertising Information Contact:
By Bill Young, WD5HOH
John Bee, N1GNV, Advertising Manager
860-594-0207 direct
860-594-0200 ARRL
860-594-0259 fax 36 HF Receiver Dynamic Range: How Much Do We Need?
Circulation Department By Peter E. Chadwick, G3RZP
Debra Jahnke, Manager
Kathy Capodicasa, N1GZO, Deputy Manager
Cathy Stepina, QEX Circulation 42 Periscopes for Microwaves: 10 GHz without Feed-Line
Offices
Loss
225 Main St, Newington, CT 06111-1494 USA
Telephone: [phone] By Paul Wade, W1GHZ
Telex: 650215-5052 MCI
Fax: [phone] (24 hour direct line)
e-mail: [email protected] 52 A Low-Loss VHF/UHF Bias Tee
Subscription rate for 6 issues: By Tom Cefalo Jr, W1EX
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Elsewhere by Airmail: ARRL member $59, 57 RF By Zack Lau, W1VT 64 Next Issue in QEX
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Members are asked to include their membership 60, 64 Out of the Box
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In order to ensure prompt delivery, we ask that May/June 2002 QEX Advertising Index
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. Active Electronics: 12 Nemal Electronics International, Inc.: 8
American Radio Relay League: 61, Palomar: 51
Copyright ©2002 by the American Radio Relay
League Inc. For permission to quote or reprint Cov II, Cov III Teri Software: 12
material from QEX or any ARRL publication, send Atomic Time, Inc.: 21 Tucson Amateur Packet Radio Corp: 41
a written request including the issue date (or book Down East Microwave Inc.: 21 TX RX Systems Inc.: 25
title), article, page numbers and a description of
where you intend to use the reprinted material. HAL Communications Corp.: Cov IV Universal Radio, Inc.: 61
Send the request to the office of the Publications Roy Lewallen, W7EL: 51
Manager ([email protected])
May/June 2002 1
Empirical Outlook
THE AMERICAN RADIO
RELAY LEAGUE
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 Freedom of Speech: An Awesome via the FCC’s Electronic Comment Fil-
the establishment of networks to provide Responsibility ing System (www.fcc.gov/e-file/ecfs.
communications in the event of disasters or other
Many of us place a very high value on html). A complete copy of the ARRL
emergencies, for the advancement of radio art
and of the public welfare, for the representation what we view as our inherent human Petition is available on our Web site at
of the radio amateur in legislative matters, and rights to freedom of speech and of the www.arrl.org/announce/regula-
for the maintenance of fraternalism and a high press. While the framers of the US Con- tory/refarm/.
standard of conduct.
ARRL is an incorporated association without stitution may have had certain ideas of Yours truly will moderate a Digital
capital stock chartered under the laws of the what constituted speech, our Supreme Voice Forum at the Dayton Ham-
state of Connecticut, and is an exempt organiza- Court has decided our rights extend to vention this year on Sunday, May 19.
tion under Section 501(c)(3) of the Internal
Revenue Code of 1986. Its affairs are governed many different forms of expression. For details of that and other inter-
by a Board of Directors, whose voting members One idea behind ensuring freedom esting Hamvention activities, visit
are elected every two years by the general of speech is to encourage people to www.hamvention.org. Be there—
membership. The officers are elected or
appointed by the Directors. The League is discuss government openly and to get you haven’t lived until you’ve been to
noncommercial, and no one who could gain involved in governing themselves. Dayton!
financially from the shaping of its affairs is Along with that goes an inherent
eligible for membership on its Board. In This Issue
“Of, by, and for the radio amateur, ”ARRL right to be heard: due process. When
numbers within its ranks the vast majority of it comes to radio regulations, you Bob Kopski, K3NHI, brings us his
active amateurs in the nation and has a proud have many chances to exercise your improvements on a wattmeter design
history of achievement as the standard-bearer in
free-speech and due-process rights that first appeared in the June, 2001
amateur affairs.
A bona fide interest in Amateur Radio is the and another chance is apparently QST. Tony Lymer, GM0DHD, has some
only essential qualification of membership; an about to present itself as I write this. notes about how to tune your antenna
Amateur Radio license is not a prerequisite,
In a Petition for Rulemaking filed without creating too much QRM.
although full voting membership is granted only
to licensed amateurs in the US. March 22, the ARRL asks the FCC to Randy Evans, KJ6PO, describes a
Membership inquiries and general corres- revise its Amateur Radio Service precise 10-MHz reference source.
pondence should be addressed to the
rules according to the modified Nov- Warren Bruene, W5OLY, took us se-
administrative headquarters at 225 Main Street,
Newington, CT 06111 USA. ice-band “refarming” plan approved riously when we stated that theory
by the League’s Board of Directors in needed to be supported by measure-
Telephone: [phone] January. ARRL adoption of the plan ment. Warren writes about some new
Telex: 650215-5052 MCI
MCIMAIL (electronic mail system) ID: 215-5052 followed the recommendations of the tries at measuring the source imped-
FAX: [phone] (24-hour direct line) ARRL Novice Spectrum Study Com- ance of an HF tuned power amplifier.
mittee, who surveyed the amateur Bill Young, WD5HOH, delivers a
Officers
community last year on the subject. combination of two popular technolo-
President: JIM D. HAYNIE, W5JBP We view this move as critical toward gies in his regenerative superhetero-
3226 Newcastle Dr, Dallas, TX 75220-1640
alleviating crowded conditions on 40 dyne receiver project.
Executive Vice President: DAVID SUMNER,
K1ZZ and 80 m and to efficient use of some Peter Chadwick, G3RZP, initiates
of our HF spectrum. Reassignment of some informed discussion of receiver
The purpose of QEX is to:
the 80, 40 and 15-m Novice CW bands dynamic range by asking, “How much
1) provide a medium for the exchange of ideas
and information among Amateur Radio is in the request. do we need?” He then uses real oper-
experimenters, If approved, the plan would expand ating conditions to answer the ques-
2) document advanced technical work in the
the phone segments on 80 and 40 m by tion, illustrating some limitations of
Amateur Radio field, and
3) support efforts to advance the state of the 25 kHz for Advanced and Extra license- traditional dynamic-range specifica-
Amateur Radio art. holders and by 50 kHz for Generals. On tions along the way.
All correspondence concerning QEX should be 15 m, Advanced and Extra operators Paul Wade, W1GHZ, returns with
addressed to the American Radio Relay League, would not see any expansion but Gen- another neat microwave antenna sys-
225 Main Street, Newington, CT 06111 USA. erals would pick up an additional 25 tem involving passive reflectors. Tom
Envelopes containing manuscripts and letters for
publication in QEX should be marked Editor, QEX. kHz. No phone-segment changes are Cefalo, Jr, W1EX, contributes a bias-
proposed for the other HF bands. tee design. The tee is handy for sup-
Both theoretical and practical technical articles
are welcomed. Manuscripts should be submitted One important justification for ex- plying power through your coax to
on IBM or Mac format 3.5-inch diskette in word- pansion of phone bands is to make room things like remotely mounted pream-
processor format, if possible. We can redraw any for digital voice and video modes. The plifiers.
figures as long as their content is clear. Photos
Petition also asks that current Novice Apologies to those of you who looked
should be glossy, color or black-and-white prints
of at least the size they are to appear in QEX. and Tech-Plus license-holders be al- hard for the review of the AADE L/C
Further information for authors can be found on lowed to operate on 80, 40, 15 and 10-m Meter model II B in the last issue! It
the Web at www.arrl.org/qex/ or by e-mail to
General-class CW allocations at up to is here this time in Ray Mack,
[email protected].
200 W output power. Such a move WD5IFS’s Out of the Box. In Tech
Any opinions expressed in QEX are those of
would allow more room for popular, Notes, Peter Bertini, K1ZJH, brings us
the authors, not necessarily those of the Editor or
the League. While we strive to ensure all material narrow-band modes such as PSK31. Rudy Severns, N6LF’s follow-on notes
is technically correct, authors are expected to We encourage you to make your- about RF current on flat conductors.
defend their own assertions. Products mentioned
selves heard by filing comments in In RF, Zack Lau, W1VT shows how to
are included for your information only; no
endorsement is implied. Readers are cautioned to favor of the Petition during the open cobble up some nifty tuning knobs in
verify the availability of products before sending comment period. You may file com- a machine shop–73, Doug Smith,
money to vendors. ments on this and other petitions KF6DX; [email protected]. (cid:2)(cid:2)
2 May/June 2002
An Advanced VHF Wattmeter

A few modifications greatly increase
QST
the utility of a popular project
By Bob Kopski, K3NHI
T
his homebrew instrument is the front panel (see Fig 1). There are these goals is a custom face for the
based on the RF power meter now two meters and more controls. analog meter plus some circuitry for
project by Wes Hayward, W7ZOI Almost all these additions are associ- the scaling and level-shifting of inter-
and Bob Larkin, K7PUA that appears ated with the instrument’s low-fre- nal signals. This signal processing re-
in QST, June 2001. The reference article quency signal processing or “support” sults in direct dBm readings on both
presented a simple instrument for the circuitry. Except for the inclusion of a meters—no conversion chart is
homebrewer to measure RF power well convenient 20-dB slide-switch attenu- needed. The DVM also displays the
through VHF. I decided to build it but ator, the original RF section is un- correct polarity sign. There’s neither
with some personalization and en- changed. rocket science nor smoke and mirrors
hancements to better suit my needs and The reference instrument incorpo- here folks: It’s all done simply with op
interests. When I sent a thank-you note rated a built-in analog meter and pro- amps and resistors! The schematic
to the designers for the original article vision to connect an external DVM. It tells all (See Fig 2).
along with some information about also utilized a conversion chart to re- In the process of designing these ba-
mine, Wes encouraged me to do this late meter readings to RF power. I sic circuit functions, it occurred to me
write-up. “Go for it!” were his words. wanted both digital and analog dis- that other simple additions would add a
If you compare this version with the plays built in for both an accurate, lot to the utility of the instrument. Thus,
original, the first thing you’ll see is high-resolution numeric power read- the project grew “on the fly.” One of
that this box has a lot more stuff on out and a trend indicator at the same these extras is a gain-change option that
time. I also wanted to avoid using a includes an external OFFSET control for
25 West End Dr calibration chart if possible. the analog display.
Lansdale, PA 19446 All that’s needed to accomplish This enhancement switches the ana-
May/June 2002 3
log meter reading from 10 dB to 1 dB per sure. I used a standard 3×4×5-inch I suggest you do some simple open
major division. The panel mounted Minibox instead. This has enough and short checks on the completed
OFFSET control allows any readable in- room for the panel, internal circuits subassembly with an ohmmeter before
put power level to be brought into the and two 9-V batteries (see Fig 3). powering it up and connecting the rea-
analog meter’s range. It’s really a “slide- My RF subassembly is shown in Fig 4. sonably expensive AD8307 on the RF
back” function. Thus, this meter can I used the original “dead-bug” technique subassembly.
change from a display calibrated in dBm on PC-board material. You can incorpo- I generally lay out instrument pan-
to a relative-dB reading. At the same rate the 20-dB attenuator, some other els with a drawing program and print
time, the DVM continues to read the operational feature or just simply follow them using an inkjet printer on good-
absolute power level in dBm. It’s the the reference article. In any case, I sug- quality paper. I stick the paper to the
best of both worlds, I think. Since the gest you stick with the original design metal box with rub-on glue stick. Not
analog panel meter responds reason- details immediately surrounding the
ably quickly, it’s like a “souped-up” AD8307 IC. I did and all works well.
trend meter, good for tuning filters and The signal-processing circuitry can be Fig 2 (right)—A schematic of the VHF
such. built in almost any way you prefer, in- power meter. All resistors are 1/ 4W, 5%
Another addition is the incorpora- cluding the original dead-bug or “ugly” carbon components unless otherwise
indicated. All capacitors are ceramic
tion of a separate signal output scaled way. I like to use PC “hole-board” for this
unless otherwise indicated.
to 10 mV/dB. This permits easy, cali- sort of thing (see Fig 5). I’ve included the C1—15 pF
brated swept displays. Thus, one could layout of this assembly for those who’d C2—0.01 μμμμμF
sweep filters, for example, and have a like to try it (see Figs 6 and 7). Here are C3-C6—0.1 μμμμμF
C7—1000 pF
very usable scope display with a a few tips to go with it. C8-C10—10 μμμμμF, 16 V, tantalum
known, convenient log-scale response. The board is cut from RadioShack C11—0.012 μμμμμF
In conjunction with this last feature, (#276-168). This hole-board has a pre- C12—150 pF
I included a switched output-band- etched IC pattern and buses on it. The C13—1 μμμμμF, 35 V, tantalum
D1, D3—1N4148 diode
width filter as shown. This was done addition of some wire jumpers makes it
D2—LED, as preferred
with the speculation that such a fea- a complete custom circuit board ready IC1—AD8307 log amplifier, (Kanga, 3521
ture might be useful with varying for the components. Please note that Spring Lake Dr, Findlay OH 45840)
sweep speeds. I’ve yet to fully exercise two wire jumpers pass under the IC IC2—LM324 quad op amp
this feature; but while I was drilling socket. Be sure to install these before the IC3—78L05 5-V regulator
M1—200 mV DVM (PM-128 panel meter
panel holes, I drilled for this too! 14-pin socket goes in. Probably the most
from Circuit Specialists, Hosfelt or as
In hindsight, I realize now I might important assembly guidance I can of- preferred)
also have included a battery-check fer is to carefully study the layout for M2—0-1 mA meter (JAMECO 171897 or as
switch to monitor the two internal 9-V parts placement and count holes! preferred)
R1, R3—61 ΩΩΩΩΩ, selected
batteries via the analog meter, since When your board assembly is done,
R2—248 ΩΩΩΩΩ, selected
it’s there anyway. (The DVM can’t carefully remove the flux, and inspect it R4—53 ΩΩΩΩΩ, selected
measure it’s own 9-V battery supply.) thoroughly with a magnifying lens for R5—470 ΩΩΩΩΩ
Oh well—I’m sure some of you can short circuits. This step helps keep R6—6.8 ΩΩΩΩΩ
think of other things that you might smoke levels under control for me. I R7, R27, R28—5.6 kΩΩΩΩΩ
R8—1 kΩΩΩΩΩ trimmer (Digi-Key 36G13-ND or
like to add for your own interests, as prefer to dress the lead wires through
equivalent)
well. some strain-relieving insulated wire R9—3.6 kΩΩΩΩΩ
loops through unused holes in the board, R10—1 kΩΩΩΩΩ
Construction as shown in Fig 5. I also prefer to twist R11, R20—3.3 kΩΩΩΩΩ
R12—22 kΩΩΩΩΩ
I do not have high ambient RF levels together multiple wires that go to a
R13—820 ΩΩΩΩΩ
and so I do not need a cast metal enclo- particular panel part such as switches. R14—200 ΩΩΩΩΩ trimmer (Digi-Key 36G22-ND
or equivalent)
R15—47 kΩΩΩΩΩ
R16—750 ΩΩΩΩΩ
Fig 1—The advanced
R17, R24—100 ΩΩΩΩΩ trimmer (Digi-Key 36G12-
VHF power meter
ND or equivalent)
includes a digital panel
R18—100 k ΩΩΩΩΩ trimmer (Digi-Key 36G15-ND
meter for accurate, high-
or equivalent)
resolution power
R19—68 kΩΩΩΩΩ
readings plus an analog
R21, R25—3.9 kΩΩΩΩΩ
meter for trend
R22—5 kΩΩΩΩΩ 10-turn potentiometer (Mouser
information. The
594-53411502 or equivalent)
instrument bottoms out
R23—220 ΩΩΩΩΩ
around –76 dBm but
R26—2 kΩΩΩΩΩ trimmer (Digi-Key 36G23-ND or
calibration very good
equivalent)
above –70 dBm.
SW1, SW3—DPDT mini-toggle
SW2—SPDT mini-toggle switch
SW4—DPDT slide switch (Digi-Key SW333-
ND or equivalent)
BNC connector
Phono jack
Box—3×××××4×××××5-inch Minibox
9 V—Eveready 522 or equivalent
9 V—6 AA cells and holder
Battery connectors (2)
PC Board-double sided
Holeboard RadioShack #276-168
14-pin IC socket
4 May/June 2002
May/June 2002 5
all glue sticks work well for this. I do I use TurboCad in both my electronic panel meter, as well. With switch SW1
this process twice. and R/C aeromodeling hobbies; but I in dBm mode, R26 sets the rate of
The first printout—an expendable think other drawing programs should change of the display while R18 makes
template—includes the drill centers be usable as well. You can also download a given power level read correctly.
and other mechanical details. I use it a useable demo version of TurboCad When all is done properly, both digital
as a drill and cutout guide. When all from www.turbocad.com. and analog meters display both the
this heavy-duty work is done, I remove same power level and the same
Calibration and Operation
the paper by soaking in water. Some changes in power level.
drying, deburring and solvent-clean- I suggest you review the discussion Incidentally, these adjustments are
ing of the Minibox readies it for the in the reference article concerning RF usually iterative in nature. Expect to go
second and final panel paper. sources for calibration of your power back and forth a few times between each
The second paper is printed with the meter. Once you have a suitable cal and offset trimmer pair until conver-
nice-looking panel details but without known source, start by calibrating the gence occurs and the respective meter
the construction markings. Once this DVM. Trimmer R14 sets the gain so reads correctly across its full range.
paper is glued in place, I overlay it with that an x-dB change in input power As above, trimmer R24 sets the gain
Contact-brand clear film for durability. results in an x-mV change in DVM for the analog meter in the decibel
The final task is to cut away the overlay reading; that is, so that 1 mV = 1 dB. mode. In this case, though, there is no
papers where the metalwork holes are; Trimmer R14 locates this result in the associated offset trimmer. Rather, the
that is easily done with an X-acto knife right place. In other words, R17 makes panel mounted OFFSET pot is used as
and a #11 blade. The result is as you see the DVM read the power level cor- needed in the application of the instru-
it. It looks good, don’t you think? By the rectly while R14 makes changes in ment. In use, it is adjusted to estab-
way, the analog meter scale is drawn power level read correctly. lish a reference reading on the analog
and printed the same way (see Fig 8). This same idea holds for the analog face (usually “0”) for any useable in-
Fig 3 (above)—What’s inside the 3×××××4×××××5-inch Minibox: A 9-V
battery for the DVM, six AA cells power everything else. The
batteries are held in place with hook and loop tape.
Fig 4(right)—The RF subassembly uses dead-bug construction
and includes a 20-dB step attenuator. It is held against case front
inside by three screws. A three-wire cable connects it to the
signal-processing board.
Fig 5—The signal-processing
board is based on a RadioShack
printed hole board. Notice the
centrally located three-pin
connector used to interface
with the RF subassembly.
6 May/June 2002
put power. Thus in this mode, the deci- such components are more readily Conclusion
bel readings of the analog meter are available.
Notice how it’s possible to expand
no longer referenced to a milliwatt Trimmer R7 calibrates the output sig-
upon one basic project and customize
(dBm), but it can accurately display nal to the design value of 10 mV/dB—
it for your own needs and interests. It’s
power changes in decibels OFFSET con- it’s another gain trim. Notice that this funny how some would call that bash-
trol. In effect, it becomes an expanded- signal output rests on a non-offsetable
ing! Now it’s your turn to duplicate or
scale meter. Because this pot must ac- dc value. That is usually of no conse-
customize your own rendition of this
commodate a very wide signal range, quence in application. If you’d prefer to
VHF wattmeter. Maybe there’s a pub-
a multiturn pot is highly recom- ac-couple this output (0.1 μF should do
lished homebrew item you’d like to em-
mended. Mine is a three-turn compo- the trick), or add an offset-control cir-
bellish or simplify. As the man said,
nent, but 10 turns would be better, and cuit, feel free to do so.
“Go for it!”
Fig 6—Component placement diagram for the signal processing board. This view is from the component side with the printed-circuit
traces and lands from the other side shown dotted.
May/June 2002 7
I’d be happy to correspond with QEX
readers. Please include a SASE with
any correspondence for which you’d
like a reply.
Bob is a recently retired Senior De-
sign Engineer with a major defense
contractor. He holds BSEE and BSEP
degrees from Lehigh University.
As a life-long electronics, ham and
aeromodeling hobbyist, he routinely
combines all three pursuits for the fun
of it. His Technician ticket dates to
about 1959, at which time he wanted
to homebrew 6-meter radio-control
equipment for R/C aeromodels. He
still routinely flies on six and has op-
erated fixed and mobile stations on six.
He has published an original six-meter
H-T. His broadly based aeromodeling
interest dates to the early 1950s, but he
has specialized in electrically powered
R/C models for over 25 years. He has
been a Contributing Editor to Model
Aviation magazine for over 19 years
with a monthly column devoted to the
electric flying specialty Additionally,
he has published many construction
articles covering both model aircraft
design and aeromodeling related elec-
tronics. He enjoys it all! (cid:2)(cid:2)
Fig 7—Wiring and jumper diagram for the signal-processing board. This view is from the
component side with the printed-circuit traces and lands from the other side shown
dotted.
Fig 8—The
original 0-1 mA
meter scale has
been replaced
with an
eye-catching
and functional
power-meter
scale. The
replacement
scale was made
using a drawing
program and an
inkjet printer.
8 May/June 2002