Digest of Articles - QST Jan 94 (Long - 47k)

Digest of Articles - QST Jan 94 (Long - 47k)

Post by W. E. Van Hor » Thu, 16 Jun 1994 02:15:50

DIGEST OF ARTICLES -- QST January, 1994

Following are digests of articles printed in the January, 1994 issue of
QST.  Such digests are being prepared for each issue of QST, and posted
periodically.  Subsequent issues will be posted one per week until they
"catch up" to the current date in mid-1994, thereafter monthly.

It is hoped that other hams will volunteer to post similar digests of
the other ham technical publications such as QEX, CQ, 73, COMMUNICATIONS
QUARTERLY, RTTY JOURNAL, et al.  Especially desirable would be digests
of publications in other countries, such as the RSGB RADIO COMMUNICA-
TIONS and ham magazines in Europe, Japan, Australia, and other countries
around the world.  We English speakers would especially enjoy them if
they were translated into our language, but they would also be valuable
additions to the world's knowledge if they were posted in the language
of origin.  Who knows?  Some bi-lingual ham somewhere might translate
them into English and re-post them.

Worldwide communications are getting better and better.  The time has
come to make the world's ham press available to all hams throughout the
world!

The major value of digests is to give readers sufficient information to
decide whether to obtain a copy of the full text.  If any U.S. reader
wants a copy of an article in QST, please inquire of other hams in your
own neighborhood.  Many have collections of back issues.  Anyone who is
unsuccessful in finding a fellow ham with a collection should try every
library in the area, especially those at universities and technical
colleges.  If all else fails, a copy can be obtained from the ARRL
Technical Department, 225 Main St., Newington, CT 06111-1494 USA for a
fee of $3.00 per copy.  Remember, it is both cheaper and quicker to
obtain one locally.

Readers in most other countries can obtain copies from their own
national ham organizations, sometimes translated into their own
languages.

-------------------------------CUT HERE---------------------------------

COPYRIGHT NOTICE: Copyright to all the following material from QST
Magazine is held by the American Radio Relay League (ARRL), effective on
the date of issue.  Permission is granted for redistribution of the
following in its entirety, or in part, provided that this copyright
notice is not removed or altered and that proper attribution is made to
ARRL as publisher of QST, to the authors of the original articles, and
to W. E. "Van" Van Horne, W8UOF, author of this compilation.
                              _________

                          TABLE OF CONTENTS

       (line number in parentheses - counting from CUT HERE line)

TECHNICAL ARTICLES (TA)

TA1:An Inexpensive SSTV System                                        69
TA2:The Nearly Perfect Amplifier                                     104
TA3:Computer-Controlled Electronic Test Equipment                    172
TA4:Uncle Albert's Unique Keyer                                      231
TA5:III - Capacitors                                                 268

PRODUCT REVIEW (PR)

PR1:The Yaesu FRG-100 General Coverage Receiver                      296
PR2:The MFJ-8100 Shortwave Regenerative Receiver Kit                 336
PR3:Heil Pro-Set Headset                                             373

HINTS AND KINKS (HK)

HK1:Ferrite Shield-Current Chokes Cure Stray RF on Vertical Antenna  413
        Transmission Lines
HK2:Another Simple Interface for Transceivers With RS-232-C Ports    439
HK3:Cutting Printed Circuit Boards                                   461
HK4:Adding Unsquelched Audio Output to the ICOM IC-228A Receiver     470
HK5:Minimizing TVI From the Yaesu FT-767GX Transceiver               494
HK6:Laundry Detergent Boxes Store QSTE                               514

TECHNICAL CORRESPONDENCE (TC)

TC1:Large Antenna Coils                                              530

NEW HAM COMPANION (NHC)

NHC1:Test Day                                                        594
NHC2:The Doctor is IN                                                603
NHC3:A CHEAP Way to Hunt Transceivers                                619
NHC4:Where's My Mail?                                                644
NHC5:Do You Need an Antenna Tuner?                                   676

RADIO TIPS (RT)

RT1:Those Versatile Hand-Helds                                       714
RT2:Packet Snooping                                                  727
RT3:Log It or Lose It                                                744

GENERAL INTEREST ARTICLES (GI)

GI1:Antenna Radio Postage Stamps                                     760
GI2:Mother Nature's Radio                                            791
GI3:Before Spark                                                     853
------------------------------------------------------------------------

TECHNICAL ARTICLES (TA)

Title>TA1:An Inexpensive SSTV System
Author>Vester, Ben - K3BC
Source>QST Jan 94, pp. 27-29
Abstract>An SSTV receive/transmit system entirely in software.  It
requires only a PC, simple interface, and conventional transceiver.

Digest>In this article the author describes his development of a
complete SSTV transmitting and receiving system done entirely in
software!  The only electronic apparatus required is an amateur
transceiver, a personal computer, and a very simple interface using one
integrated circuit (IC), plus a dozen passive components.

He has made the software available free, and it can be downloaded from
the ARRL Bulletin Board at (203) 666-0578.  The name of the file is
"vester.zip".

The kernels of the program are written in assembler language for speed
and efficiency, but additions and modifications can be made in Basic and
"hooked" onto the kernel using "POKEs".

The computer requirements are a DOS machine using an 80286, or later,
microprocessor, although a '386 or better at 16- or 33-MHz. clock rate
will give definitely better results.  It should have a VGA-compatible
color monitor and a "Super VGA" (SVGA) video adapter card.

The transceiver can be any conventional SSB rig on HF, VHF, or UHF.  If
it is to be used with an AM or phasing-type SSB rig, or with FM
transmitters, audio filtering will probably be required to assure
sufficient spectral purity for good pictures.

The article shows a number of photographs of the author's CRT screen.
The color and resolution are very impressive, indeed.
                               _________

Title>TA2:The Nearly Perfect Amplifier
Author>Measures, Richard - AG6K
Source>QST Jan 94, pp. 30-34
Abstract>Auxiliary and protective circuitry that can be added to any
tube-type amplifier, greatly enhancing reliability and operating life.

Digest>The title to this article might more properly be called "The
Nearly Perfect Protective and Auxiliary Circuits for an Amplifier".  The
author makes a thorough and penetrating analysis of the auxiliary
circuitry of a tube-type RF power amplifier, but does not discuss the RF
aspects, at all!  He does an excellent job of pointing out how
relatively inexpensive additions and modifications can greatly improve
the reliability and life, as well as the performance, of most modern
commercially-built amplifiers.

He considers each aspect of the power tube and power supply, in turn.
First, he addresses the extreme sensitivity of a power tube's operating
life expectancy to tiny changes in filament voltage and strongly
recommends a voltage-regulated power supply.  Second, he makes a
convincing case that EVERY power tube should have a time-delay circuit
to apply reduced voltage to the filament for a warm-up period before
raising it to full rated voltage.

Regarding the grid circuit, he observes that he has never seen an
amplifier damaged by excessive HF grid current, but excessive grid
current caused by VHF or UHF parasitics is a very common cause of tube
destruction.  Nevertheless, many commercial amplifiers are built with
protective circuits to prevent excessive HF grid current but with
totally inadequate parasitic suppression.  He recommends a foolproof
method of protecting the grid, which is insertion of a carbon-film
resistor as a fuse.

Another very common cause of severe damage to amplifiers is from
accidental shorts of the high-voltage to ground.  They can be caused by
insects, fine threads sucked into the blower, or a myriad of other
causes.  At the instant of a short, the full charge in the power-supply
filter capacitors is delivered and a peak current of hundreds of
amperes passes through the plate current meter and, probably, causes an
arc at the point where the short occurred.  He cites one case in which
the meter exploded!.

At the instant of the capacitor discharge caused by a short, the
negative high-voltage will surge to several kilovolts.  The grid-current
meter, normally connected from the negative high-voltage terminal to the
chassis will thus also be subjected to a surge of hundreds of amps.
Simultaneously, if the tube uses an indirectly-heated cathode, the
negative high-voltage surge may cause an arc from the cathode to the
filament, destroying the tube.  All of this damage can be prevented by
the liberal use of protective diodes that cost about 20-cents each!

Next, the author looks at power supplies.  The common use of parallel
resistors and capacitors across each rectifier diode in a high-voltage
rectifier is shown to be self-defeating.  Instead, he recommends
metal-oxide varistors.  The voltage across filter capacitors should be
equalized with resistors across each series capacitor, but care must be
used to choose the proper resistor.  He recommends 3-watt, 100,000-ohm
metal-oxide-film resistors for 450-volt capacitors.

The article concludes with several other recommendations regarding
high-speed receive/transmit relays, VHF parasitic suppressors, and some
other suggestions for specific cases.  The author summarizes by pointing
out that the total cost of everything that he recommends would likely
not exceed $100, and might be considerably less.  The end result would
be a dramatic improvement in operation and safety of almost any
amplifier on the market today.
                               _________

Title>TA3:Computer-Controlled Electronic Test Equipment - Part 2
Author>Portugal, Ron
Source>QST Jan 94, pp. 35-41
Abstract>Construction of a "mother board" to hold instruments to be
built as described in future installments.  Also construction details
for building an L-C meter covering ranges of 1-microhenry to 5-henrys
and 1-picofarad to 10,000-microfarads.

Digest>In this installment, the  author describes the construction of a
"mother board" to hold all of the instruments to be built.  Considering
the total number of cables, leads, jumpers, and miscellaneous wires that
would otherwise decorate the workbench, the use of a mother board that
contains all the interconnecting wires on its etched surface can be seen
to be a great advantage.  The board is 12.5 x 7 inches (318 x 178 mm.)
and contains 9 50-pin headers, each of which will accept a 5 x 6 inch
(127 x 152 mm.) project board.  In addition, there is a single 50-pin
socket to expand the bus onto a second chassis, for future expansion.

The power supply, construction of which was described in Part 1, is the
first module to be installed on the mother board.  The rest of this
article is devoted to the construction of an L-C meter.  It provides an
unusually wide measurement range of both variables.  It measures
inductance over a range of 5-million-to-1 (5-henrys to 1-microhenry).
The capacitance range is even greater, 10-million-to-1 (10,000-
microfarads to 1-picofarad).  Readout is on a 4-digit counter.  Accuracy
is determined by the precision of the components used but, since the
measurements are developed in the computer, any errors can be removed by
calibration using any arbitrary number of standard capacitors and
inductors to establish points on the curve.

Capacitance is measured by using the fact that if a capacitor is charged
from a known voltage source through a known resistance, its charging
rate is a measure of the capacitance.  The meter measures the length of
time the unknown capacitor requires to charge from one known voltage
level to another.

Inductors are measured by pairing them with known capacitors to form
oscillator tank circuits.  The frequencies of the resulting oscillations
are measured and the inductance calculated from the resonance equation:
L=1/C*(2*pi*f)^2.

From the preceding description, it can be seen that the raw measurements
of both capacitances and inductances are time durations expressed as
numbers of cycles counted in the signal from an oscillator.  The
oscillator used in capacitance measurement is a high-precision
square-wave generator; in the inductance measurement, the oscillator is
controlled by the L-C tank circuit.  In both cases, the cycles are
counted and the result entered into registers in the computer for
conversion to engineering units.

The author is offering partial kits of parts for both the mother board
plus power supply, and the L-C meter modules.  His price for the former,
including shipping in the continental United States, is $100.  For the
L-C meter, $81.  The only parts not included are a mounting frame for
the mother board and a power switch with LED indicator for the power
supply.
                               _________

Title>TA4:Uncle Albert's Unique Keyer
Author>Ulbing, Sam - N4UAU
Source>QST Jan 94, pp. 42-44
Abstract>Construction of a keyer that displays ASCII characters as they
are formed, and the code speed, on an LCD display.

Digest>This article describes construction of a keyer combined with a
code reader that displays the ASCII characters that are being sent on a
ticker-tape-like LCD display.  It also calculates the code speed and
displays the words-per-minute on the same display.

The keyer can be actuated be either an iambic key or an external bug.
It also includes a 47-character memory and a random-character
code-practice generator that displays what it sends.  It can be actuated
at speeds ranging from 8- to 40-wpm.

The author's main goal in designing the code-reader and display was to
improve the sender's "fist".  The code reader does not lie.  If the
sender runs the letters together and, for example, makes "ti" into "d",
the display shows it.  If s/he forms an unintelligible character, the
display shows an "&" (ampersand).  Most CW operators would consider it a
blessing if all other operators would use such a device!

A complete wiring diagram and parts list is included.  The unit uses a
microcontroller type 87C51, the LCD display module, and a mere handful
of other parts: 3 transistors, 4 diodes, an oscillator crystal, and
about a dozen resistors and capacitors.

The author offers a pre-drilled PC-board and a pre-programmed
microcontroller with construction information and operating
instructions for $38; a more complete parts kit including all electronic
parts excepting only the enclosure and miscellaneous hardware for either
$60 or $67, depending upon LCD size.  He does not offer his software
separately.
                               _________

Title>TA5:III - Capacitors
Author>Bergeron, Bryan - NU1N
Source>QST Jan 94, pp. 45-48
Abstract>Elementary description of capacitors used in radio circuits.

Digest>This is the third article in a series describing and illustrating
electronic parts.  Types of capacitors are described, illustrated in
photographs, and the symbols used in circuit diagrams.  The electrical
characteristics of the various types are discussed in detail.

The types of capacitors discussed at length are: electrolytics, film,
air-variables, ceramics, mica, oil, and paper.  Electrolytics are
sub-classified as aluminum or tantalum; film as polypropylene,
polyester, polycarbonate, polystyrene, polysulfone, or metalized
film.

Electrical characteristics described are capactitance, tolerance, rated
voltage, equivalent series resistance, dissipation factor,
dielectric loss-angle, frequency ratings, operating temperature limits,
leakage current, temperature coefficient, power-handling capability, and
expected operating life.  The schemes used in labeling small capacitors
is explained.
------------------------------------------------------------------------

PRODUCT REVIEWS (PR)
        Conductor: Mark Wilson - AA2Z
                   QST Editor

Title>PR1:The Yaesu FRG-100 General-Coverage Receiver
Author>Newkirk, David - WJ1Z
Source>QST Jan 94, pp. 73-75
Abstract>Review of Yaesu's FRG-100 receiver for the SWL market.
Performance is good enough to rate as a respectable amateur station
receiver.

Digest>The Yaesu FRG-100 is a receiver designed for the Short Wave
Listener market but performs well enough to do a respectable job as an
amateur station receiver.  In fact, it offers one performance feature
that most current amateur transceivers do not provide.  In CW operation,
one can select the sideband being received.  This, combined with RIT and
variable pitch control allows one to use zero-beat as the ultimate audio
notch filter.

The circuit design is completely new; it is not just the receiver
portion extracted from the design of one of the current Yaesu
transceiver models.  It comes with 52 programmable memories that store
both frequency and mode, digital frequency counter with readout to the
nearest 10 Hz., scanning of either the memory bank or the band,
clock/timer, and switchable i.f. selectivity of 2.4-, 4-, and 6-KHz. as
standard.  Optional features available are: CW crystal filters - 250 and
500 Hz. width, FM reception, and a high-stability crystal synthesizer.

It does not include a preamplifier, but its sensitivity on SSB and CW
for 10 dB. signal-to-noise ratio is better than 0.25 microvolts.  With a
500 Hz. CW filter, the noise floor was measured as better than -138 dBm.
on both 80- and 20-meters.  The dynamic range measured better than 113
db. on the same two bands.  The third-order intercept was 1.5 dBm. on
the 20-meter band.

The receiver's first i.f. is at 47 MHz. and its image rejection is
better than 60 dB. over the entire 1.8- to 30-MHz. HF range.  The
reviewer's final summary states: "...the compact FRG-100 packs a
surprising performance wallop at a price that should make its
competition worry."  That price (list) is below $900, including one CW
filter and the FM receiving unit.
                               _________

Title>PR2:The MFJ-8100 Shortwave Regenerative Receiver Kit
Author>Newkirk, David - WJ1Z
Source>QST Jan 94, p. 76
Abstract>Review of a kit for building a regenerative receiver, using
modern components.  The completed unit gives surprisingly good
performance in a very small, lightweight, attractive package.

Digest>Many old-time hams have speculated about the result of someone
using modern components and construction techniques to build a receiver,
the design of which dates from pre-superheterodyne times.  Now they can
find out by building a kit available from MFJ.  The result will be a
receiver of surprisingly good performance built in a small, lightweight,
and very attractive cabinet, powered by a single 9-volt battery.

The circuit would be a classic "TRF" (Tuned Radio Frequency) except that
the r.f. amplifier stage is broadbanded, not tuned.  It uses three JFETs
and an integrated-circuit audio amplifier.  One of the JFETs is an
untuned, grounded-gate r.f. amplifier and the other two are used as a
Butler-oscillator regenerative detector.  The detector's tuned circuit
is switched over five bands from 3.5- to 22-MHz.  The tuning capacitor
has a built-in 6:1 reduction drive which, the reviewer found, "tunes the
receiver well".

The ARRL laboratory put the little receiver through performance tests
similar to those given to the latest state-of-the-art superheterodyne
receivers and found a quite-respectable sensitivity of -105 dBm. at 4-
and 10-MHz.  At 20-MHz., it was -90 dBm.  Of course, with no tuned
circuit ahead of the detector, the selectivity is not very good but
nevertheless, its two-tone, third-order dynamic range measured 70 dB.
with 100-KHz. tone spacing.

This receiver would seem to be a fitting partner with a QRP rig to test
the limits of communications using minimum equipment.  In addition, it
would be a nostalgia trip for many old timers!
                               _________

Title>PR3:Heil Pro-Set Headset
Author>Wilson, Mark J. - AA2Z
Source>QST Jan 94, p. 77
Abstract>A headset with integral microphone designed for professionals.

Digest>The Heil Pro-Set is a stereo headset/microphone combination
assembly designed for professional use.  The headband is thoroughly
padded and adjustable with detents.  The cushions on the ear pieces are
replaceable and comfortable.  The ear pieces are attached to the
headband through a ball joint that allows considerable variation in
angle in order to provide a comfortable fit for people with varying size
and shape heads.  The microphone is attached to the assembly by a
swiveling boom that can also be adjusted in shape.  It is easy to place
the mike at its most comfortable location or to swivel it up and out of
the way when it is not in use.

The cabling from both ear pieces and the microphone pass through a
common cable.  At the plug end, the headphone plug is a conventional
1/4-inch (6-mm.) stereo phone plug.  The microphone plug, however, is a
1/8-inch phone plug.  In use, it is plugged into a mating socket on one
end of a 12-inch (30-cm.) jumper, the other end of which terminates in a
plug selected to fit the user's specific requirement.  Transceivers
differ in the microphone connector and Heil provides a selection of
jumpers to fit.  A purchaser of the headset is given a choice of jumpers
included in the purchase price.  Additional jumpers can be bought
separately.

The reviewer found that the headphones "sound great", they are
comfortable to wear for extended periods, and the microphone produces
audio that is "clean, crisp, and punchy".

The list price, including one jumper, is $135; additional jumpers $13
each.
------------------------------------------------------------------------

HINTS AND KINKS (HK)
        Conductor: David Newkirk - WJ1Z
                   Sr. Asst. Technical Editor
                               _________

Title>HK1:Ferrite Shield-Current Chokes Cure Stray RF on Vertical-
        Antenna Transmission Lines
Author>Palmer, Bruce R. - K0WM
Source>QST Jan 94, p. 78
Abstract>Construction of an antenna feedline ***using ferrite cores
strung on a piece of coax.

Digest>The author had considerable difficulty resulting from r.f.
feedback in his shack when using his Kenwood TS-940S and a kilowatt
amplifier.  He found that a ferrite-bead shield-current ***in the
antenna feedline where it enters his shack solved the problem.

He built the ***using 50 Type FB73-2401 ferrite beads, 15-inches
(38-cm.) of RG-303 coax, and two coax connectors.  He used PL-259 plugs
with inserts designed for RG-58 cable, which is larger in diameter than
the RG-303.  To make a good fit, he put a 1-inch (2.5-cm.) length of
heat-shrink tubing over the cable at the point where the connector was
to be attached.

To assemble the choke, he installed a connector on one end of the coax,
threaded on the 50 beads, and put a length of heatshrink tubing over the
entire string of beads to hold them in place.  Then he finished the job
by installing another PL-259 on the other end.
                               _________

Title>HK2:Another Simple Interface for Transceivers with RS-232-C Ports
Author>Shelhamer, Mark - WA3YNO
Source>QST Jan 94, p. 78
Abstract>Interface converting RS-232-C voltage levels to TTL, and vice
versa, using readily available components.

Digest>In Hints and Kinks, QST Jan 92, WB4ETY described a simple level
converter for connecting TTL-level serial ports to RS-232-C ports.  The
level conversion is often required because TTL-level voltages are 0 and
+5, whereas RS-232-C levels are bipolar.  However, some computer
RS-232-C interfaces will work with TTL level signals, and no level
conversion is needed for signals going from the transceiver to the
computer.  However, the RS-232-C levels from the computer back to the
transceiver must be clipped, or voltage-limited, to avoid damage.

For such cases, Mr. Shelhamer presents a circuit diagram using a single
74LS08 low-power Schottkey chip to make the interconnections.  The
circuit is not as simple as WB4ETY's, but it utilizes a chip that is
much more readily available than the Maxim MAX232 that he used.
                               _________

Title>HK3:Cutting Printed Circuit Boards
Author>Gibson, Roger - K4KLK
Source>QST Jan 94, p. 79
Abstract>An office-type paper cutter does an excellent job cutting PC
board material, but the blade dulls rapidly and becomes useless for
cutting paper.
                               _________

Title>HK4:Adding Unsquelched Audio Output to the ICOM IC-228A Receiver
Author>McLellan, Scott W. - ND3P
Source>QST Jan 94, p. 79
Abstract>Adding a separate unsquelched audio output for packet so the
operator can continue to listen to the squelched output.

Digest>The author uses his ICOM 2-meter rig for both packet and voice.
Because of the time delay in opening squelch, he operates the rig with
its squelch wide open.  To avoid annoying noise when no signal is
present, he added an extra audio output line that is not squelched for
use on packet so that he can leave the normal squelch setting in use but
still have instant packet operation.

To carry the unsquelched audio signal to the TNC, he disconnected the
lead that previously used pin number 4 on the microphone jack.  He
obtained the unsquelched audio signal by tapping into the audio
amplifier chain in the receiver portion at a point indicated in the
schematic illustrated in the article.

The signal that was previously carried on pin 4, which he disconnected,
was "T.SQL BUSY", which was never used in his modes of operation.
                               _________

Title>HK5:Minimizing TVI From the Yaesu FT-757GX Transceiver
Author>Lee, Mitchell - KB6FPW
Source>QST Jan 94, p. 79
Abstract>Stopping leakage of r.f. out through the power cord.

Digest>Mr. Lee's transceiver generated TVI even when he was using a
dummy antenna.  He found that harmonics were leaking out of the rig
through the 12-volt power cord.  He lists 4 steps that may be
used to stop the leakage: (1) Isolate the d.c. input line to the final
amplifier.  Current is carried by two Teflon-insulated wires from the
power connector to the amplifier board.  Slip as many ferrite and
powdered-iron toroids and sleeves as possible over both. (2) While the
wires are still disconnected, add by-pass capacitors at the Jones plug.
(3) Check for TVI using the dummy antenna.  If some is still occurring,
go to step 4; otherwise the job is finished. (4) Shield the power cable
using large diameter braid.  Connect a banana plug to the braid at the
transceiver end and plug it into the adjacent ground lug.
                               _________

Title>HK6:Laundry-Detergent Boxes Store QST
Author>Steinhorst, Ted - KA2BIG/7
Source>QST Jan 94, p. 79
Abstract>Boxes the right size to hold one year's QSTs.

Digest>The author has discovered that a 9-pound, 13-ounce (4.45 kg.)
size box of the detergent ALL will hold more than a year's worth of QSTs
upright.  To prepare the empty box for this use, he makes a diagonal cut
across the front, whereupon it becomes a fine "poor man's" magazine
holder.
------------------------------------------------------------------------

TECHNICAL CORRESPONDENCE (TC)
        Conductor: Paul Pagel - N1FB
                   Associate Technical Editor

Title>TC1:Large Antenna Coils
Author>Johns, Bob - W3JIP
Source>QST Jan 94, p. 80
Abstract>Describes a method of building large, heavy antenna coils.

Digest>This letter describes, and illustrates with a drawing, a method
of construction of very large and relatively heavy antenna coils.  They
are wound of copper tubing held in place by three spacers located around
the periphery of the coil at 120-degree angular spacing.

The spacers are made of PVC pipe split longitudinally.  The two halves
of the pipe are squeezed on either side of the coil turns and drawn down
tightly with 3 or more sets of nuts and bolts.  A notch is cut in each
half of the pipe at the point where the coil turns are clamped, thereby
firmly holding them in place.

The drawing shows the assembled coil and the pieces of pipe that form
the spreaders connected together using elbows, tees, and sections of
pipe leading to a coupling that is screwed onto the end of the "metal
element" of the antenna.  The drawing is not dimensioned, but the use of
so many pipe fittings in the mechanical support implies that the
antenna, coil, and all, are very large, indeed.
                               _________

Title>TC2:More on Electrical Protection Devices
Author>Hart, Lee A. - N8DUA
Source>QST Jan 94, pp. 80-81
Abstract>Additional means of protecting against reversed-polarity power
supply.

Digest>This letter adds suggestions for protection against reversed-
polarity power supply, supplementing the ideas in Covington's article in
QST Jul 93, pp. 40-41: "Reverse-Polarity Protection for Your Gear".  The
following suggestions are included in the letter:
  (1) Schottkey diodes have only half the voltage drop of silicon
        diodes, but their PIV ratings are limited to 20- to 40-volts.
  (2) Germanium diodes have even lower voltage drop and can have PIV as
        high as 200 volts.
  (3) For high currents, use a PNP germanium power transistor as a
        diode.  Tie the base to the collector to act as the cathode and
        use the emitter as the anode.
  (4) Use a high-power bipolar transistor wired with the input voltage
        to the emitter, the output from the collector, and the base tied
        to ground through a resistor chosen to hold the base current to
        from 2 to 10 percent of the peak output current.  If the input
        voltage will exceed plus/minus 6 volts, add a blocking diode in
        series with the base resistor.  This circuit protects not only
        against reversed polarity, but also against a dead short on the
        output.
  (5) Use a bridge rectifier between input and output.  This not only
        protects against damage due to reversed polarity, but also
        corrects it.
  (6) Use a relay: put a blocking diode in series with the relay coil so
        it will actuate only if the polarity is correct.
------------------------------------------------------------------------

NEW HAM COMPANION (NHC)

        The New Ham Companion is a regular monthly section in QST that
concentrates on articles of primary interest to newcomers to ham radio.
                               _________

Title>NHC1:Test Day
Author>Bowles, Chester S. - AA1EX
Source>QST Jan 94, pp. 62-63
Abstract>A description of what happens during a license exam session;
describes the functions of the Volunteer Examiners; and lists what is
required of the examinees.
                               _________

Title>NHC2:The Doctor is IN
Author>Various
Source>QST Jan 94, p. 64
Abstract>Questions and answers, general.

Digest>In this monthly column, questions discussed this month are: the
correlation, if any, between S-meter readings and RST reports; a method
that sometimes works to enhance the printing on aged glass vacuum tubes
to identify the tube number; the meaning of solar flux, A-index and
K-index; the meaning of QSZ; the slight delay that most transceivers
exhibit between the actuation of the push-to-talk button and when the
rig actually begins to transmit; and the "World-Wide Packet Pals
Directory".
                               _________

Title>NHC3:A CHEAP Way to Hunt Transmitters
Author>Rickerd, Glen - KC6TNF
Source>QST Jan 94, pp. 65-66
Abstract>Direction finding with an HT and a foil-wrapped mailing tube.

Digest>This article outlines a very simple and surprisingly effective
way that any hand-held VHF/UHF rig can be made into a radio direction
finder.  One needs only a mailing tube with sufficient diameter that the
rig can be inserted into it.  Wrap the tube with aluminum foil and
secure it with tape.  Hold it vertically and, while listening to a
signal, lower the HT into the tube until the signal strength begins to
drop.  The HT should be suspended from a cord or carrying strap.  Hold
tube and all against your chest and tune in the signal being sought.
Turn your body slowly around, noting the difference in signal strength.
You will notice a deep null that will be quite sharp at some particular
bearing.  At that bearing, your back is directly facing the direction
from which the signal is being received.  That is all there is to it!

This method works because your body is acting as an attenuator of
signals being propagated directly from your rear.  Putting the HT into
the tube reduces the signal level to the point that the apparent
sensitivity of the null is enhanced.
                               _________

Title>NHC4:Where's My Mail?
Author>Patterson, Dave - WB8ISZ
Source>QST Jan 94, p. 67-69
Abstract>Using the Amateur Packet Radio Network.

Digest>This article describes the Amateur Packet Radio Network, how it
works, and how to use it.  It is made up of dedicated hams who volunteer
their efforts and their equipment to the task of transmitting messages
for no compensation other than the satisfaction of getting the job done.

With very few exceptions, every ham in the "lower 48" states is always
within easy reach of a packet bulletin board system (PBBS) which s/he
can use to tap into the network and send or receive messages to and from
other hams.  All the sender/receiver needs is a 2-meter FM transceiver
(even an H-T), a terminal-node controller (TNC), and a computer.

To send a message to another ham, it is only necessary to know the radio
address of the PBBS where the intended recipient picks up his/her mail.
The sender composes a message in the manner described in the article and
sends it by packet to the local PBBS.  The computer at the local PBBS
scans the address, and "decides" from information stored in its memory,
to which PBBS it should be sent to advance it toward its ultimate
destination.  This happens again and again until the message arrives at
the destination PBBS, marked for the recipient to claim.

The author urges all hams to participate in this pleasurable aspect of
amateur operating.  For further information, he recommends obtaining a
copy of YOUR PACKET COMPANION, by Steve Ford, WB8IMY, published by the
ARRL.
                               _________

Title>NHC5:Do You Need an Antenna Tuner?
Author>Ford, Steve - WB8IMY
Source>QST Jan 94, pp. 70-72
Abstract>Description of antenna tuners and their uses.

Digest>This is a brief explanation of what an antenna tuner is, what it
does and, equally importantly, what it does not do.  One should use an
antenna tuner if:
  (1) You want to use open-wire feedline to the antenna.
  (2) If you want to operate the antenna on bands other than the one for
        which it was cut.
  (3) The antenna has a narrow SWR bandwidth.

One should not bother with an antenna tuner if:
  (1) The indicated SWR without a tuner is 1.5:1 or less.  Making the
        SWR seen by the transmitter less than 1.5:1 will yield no
        additional benefits; it is good enough the way it is!
  (2) At VHF/UHF.  Use of an antenna tuner will reduce the SWR "seen"
        by the transmitter but will not affect the SWR on the feedline.
        High SWR on a feedline at VHF/UHF causes very high loss of power.
        The problem must be corrected at its source: the antenna.
  (3) If you are suffering to TVI.  Contrary to common opinion, use of
        an antenna tuner will probably have little effect on
        interference problems.

Various features to look for in antenna tuners are explained, such as
roller- or tapped-inductors, built-in SWR meters, a built-in balun, and
others.  Also the author makes recommendations regarding power ratings
and whether to buy or build a tuner.
------------------------------------------------------------------------

RADIO TIPS (RT)

These are short items, scattered among the articles in the NEW HAM
COMPANION section.
                               _________

Title>RT1:Those Versatile Hand-Helds
Author>Kleinschmidt, Kirk - NT0Z
Source>QST Jan 94, p. 66
Abstract>General description of hand-held VHF/UHF transceivers (HTs).

Digest>The author makes a persuasive case for the fun of using a
hand-held VHF/UHF FM transceiver.  He describes using it to access a
repeater, using it from an automobile, or while walking around a flea
market to keep in touch with friends.  He also suggests using it from
the shack with an outdoor antenna, and with a TNC, in the packet mode.
                               _________

Title>RT2:Packet Snooping
Author>Ford, Steve - WB8IMY
Source>QST Jan 94, p. 69
Abstract>Monitoring packet traffic to learn about local activity.

Digest>Newcomers to packet radio can find out what is going on in their
area by using the command: MCOM ON, which causes the system to display
every packet it hears on a particular frequency.  Some TNCs use a
variation of MONITOR, rather than MCOM, to do the same thing.

From watching this activity, one can learn the call signs of local
PBBSs, personal mailboxes, nodes, and digipeaters.  Then s/he can try
connecting to some of these stations and will soon learn which are
within reach and which are out of range.
                               _________

Title>RT3:Log It or Lose It
Author>Kleinschmidt, Kirk - NT0Z
Source>QST Jan 94, p. 72
Abstract>Using a station log book.

Digest>All hams are encouraged to use a log, even though it is no longer
required by FCC regulations.  A record of QSOs is necessary for awards
and contests; it is also a good place to record changes of equipment,
maintenance procedures performed, or modifications made.  Also for
memory's sake, it is a lot of fun to review old logbooks and recall
pleasant QSOs.
------------------------------------------------------------------------

GENERAL INTEREST ARTICLES (GI)
                               _________

Title>GI1:Amateur Radio Postage Stamps
Author>Welsh, Bill - W6DDB
Source>QST Jan 94, pp. 22-26
Abstract>Summary of postage stamps that have been issued honoring ham
radio.

Digest>Many countries in the world, including the USA, have issued
stamps that honor ham radio, or for other reasons are of special
interest to hams.

This article explains how stamps can be obtained, how they should be
handled, stored, and/or exhibited as a collection, and the fact that
some collectors prefer to collect blocks of stamps or "covers" bearing
the stamps, rather than just the stamps, themselves.  "Covers" are cards
or envelopes to which the stamps are affixed and which, perhaps, have
been sent throught the mail.

As a 2-page "side-bar" with the article, is a list of the stamps that
have been issued by many countries specifically honoring ham radio.  The
author has assembled a larger list of stamps that are of special
interest to hams, although they do not specifically honor ham radio, per
se.  That list may be obtained for an SASE sent to Technical Department
Secretary, ARRL, 225 Main St., Newington, CT 06111; ask for the "Stamp
List".

The article also includes a list of "Sources of Help", including the
addresses of certain stamp dealers who specialize in amateur radio
stamps.
                               _________

Title>GI2:Mother Nature's Radio
Author>Schneider, David - AD4CC
Source>QST Jan 94, pp. 49-51
Abstract>VLF signals from natural causes.

Digest>Phenomena that occur in earth's atmosphere and in adjacent outer
space cause a variety of radio signals at very low frequencies.  In
fact, most of them are at frequencies normally considered audio, i.e.
under 20 KHz.  But they are electromagnetic, not acoustic, so can only
be detected by a radio receiver.

Modern hams may be surprised to learn that radio waves at audible
frequencies can propagate for long distances.  But the pioneers of early
radio were very aware of it.  Much traffic was handled at frequencies
below 20 KHz in the 1920's and '30's.

Natural radio noise, or QRN, is caused primarily by lightning and by
emanations from the sun.  Thunderstorm static is well known to everyone,
and is a very broad-band effect, but most of the radio energy is
concentrated at frequencies below 5 KHz. for a very good reason.  The
wavelength of a 5 KHz. radio signal is about 60 km. (36 miles).  This is
the same order of magnitude as the height of the D-layer that defines
the ionosphere, so the space between it and the ground acts as something
like a waveguide.  Using it, "ground wave" signals easily propagate
around the world.

Compiler's Note: During World War 2, the USAAF Weather Service
maintained a long-range storm tracking net (called "Sferics") that
accurately plotted the positions of thunderstorms across thousands of
miles of both the Atlantic and Pacific Oceans.  The nets used simple
radio direction finders operating at 10-KHz., with several stations
based on islands hundreds of miles apart, to get precise triangulation
on the positions of lightning strikes.

The same lightning-induced signals also propagate through distances
even more vast using the earth's magnetosphere.  In this way, very low
frequency radio waves leave the earth and travel through a great loop of
more than 100,000 miles (170,000 kms.) in a beam that is approximately
aimed at a spot in the opposite hemisphere at about the same longitude
and the opposite latitude (the "conjugate point") from where it
originated.

During transit the magnetosphere, the lower frequency components of the
static are delayed relative to the high frequencies. Consequently, when
one listens to the raw signal, that is the acoustic signal that
accurately reflects the frequencies of the radio signal, one first hears
the high frequency; over a second or two, it rapidly drops to a low
frequency.  This is called a "Whistler".  There is so little attenuation
of the signal during its passage through the magnetospere that the same
signal can bounce back and forth several times between the point of
origin and the conjugate point.  The more bounces that the signal takes,
the greater is the time delay between the high- and low-frequency
components.  Accurate recordings of Whistlers give valuable information
regarding the ionosphere and the magnetosphere.

Amateurs can help by recording Whistlers, in cooperation with studies
now being conducted by NASA and by Northern Kentucky University with a
NASA grant.  The author requests that interested hams contact him at:
Northern Kentucky University, Department  of Physics and Geology,
Highland Heights, Kentucky 41076.
                               _________

Title>GI3:Before Spark
Author>McElroy, Gil - VE1PKD
Source>QST Jan 94, pp. 57-59
Abstract>Wireless communications before radio.

Digest>Most people believe that Marconi "invented" radio.  To some
extent, he deserves that credit because he made a practical
communications system out of what was, before his work, an obscure
laboratory phenomenon.  But other experimenters had succeeded in
transmitting intelligible electrical signals over appreciable distances
decades earlier than Marconi's work.  This article describes some of
them.

Samuel F. B. Morse, after he perfected the telegraph, experimented with
wireless telegraph using water to carry the electric current.  In 1842,
he succeeded in transmitting a telegraph signal across a river, a
distance of nearly a mile.

The first person who succeeded in transmitting through air was
apparently Dr. Mahlon Loomis, a dentist.  At the close of the Civil War
in 1865, he flew two kites, carrying wires, from mountain tops 14-miles
(23-kms.) apart.  The wire from one kite was attached to ground through
a telegraph key; the other kite-wire was grounded through a galvanometer
that could measure very small currents.  When he operated the key,
detectable changes of current occurred in the other kite wire.  He was
granted a patent on his system in 1872, but no known attempt was made to
make use of the phenomenon commercially.  Interestingly, the experiment
was duplicated 44 years later in London where, during a hailstorm,
experimenters successfully communicated over a distance of 3-miles
(5-km.)

In a parallel development, the idea of communicating by electrical
induction occurred to numbers of people.  In 1845, John Wilkins of
Britain, proposed communicating across the English Channel by
electro-magnetic induction.  Not until 1891 was a successful
demonstration of such communication made.  That was done by an American,
John Trowbridge.  Using enormous wire coils mounted on a ship, he
demonstrated that he could induce signals in a similar coil on the shore
over a short distance, but even he admitted that he saw no practical
value in the system.

A few years later, several individuals conducted experiments to create
"wireless telphony".  The most successful one was Nathan B.
Stubblefield, who demonstrated two telephones communicating by an
inductive link in Murray, Kentucky in 1902.  His coils were not tuned,
but he stated his intention to develop a method by which several,
separate communications could be conducted using the same coils at the
same time, implicitly anticipating some aspects of radio.  His
experiments convinced the Legislature of the State of Kentucky which, in
1944, resolved that Nathan B. Stubblefield was "the true inventor of
radio".
------------------------------------------------------------------------