Digest of Articles - QST Jul 94 (Long - 49k)

Digest of Articles - QST Jul 94 (Long - 49k)

Post by W. E. Van Hor » Wed, 10 Aug 1994 19:14:31

DIGEST OF ARTICLES - QST July, 1994

Following are digests of articles printed in the July, 1994 issue of
QST.  Such digests are being prepared for each issue of QST, and posted
periodically.

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 SWR Detector Adapter                                           76
TA2:A Pocket Size, Talking Morse Code Practice Computer              111
TA3:The Null Steerer Revisited                                       157
TA4:144-MHz Sporadic E                                               200
TA5:Key Components of Modern Receiver Design - Part 3                266

PRODUCT REVIEW (PR)

PR1:ETO Alpha 89 Linear Power Amplifier                              319
PR2:Radio Shack DSP Communication Noise Reduction System             359
PR3:Willco Electronics ICM-1024 Memory Replacement Board             395

HINTS & KINKS (HK)

HK1:Improved Receive Performance for the Kenwood TS-450S/AT          436
        Transceiver
HK2:Silent Full Break-In Transceiver TR Switching for the Alpha 87A  464
HK3:Try Diversity Reception and Transmission                         494
HK4:Reduced Frequency Drift During CW Operation With the             523
        Ten-Tec Scout

TECHNICAL CORRESPONDENCE (TC)

TC1:Subject: MOVs                                                    555
TC2:North Shadow                                                     605

FEEDBACK (FB)

FB1:"A Calibrated Noise Source for Amateur Radio" QST May 94         643
FB2:"Small, High-Efficiency Loop Antennas", QST Jun 86               656
FB3:"Amateur Use of Telescoping Masts" QST May 94                    669

NEW HAM COMPANION (NHC)

NHC1:The Doctor is IN                                                681
NHC2:Understanding Signal Strength                                   695
NHC3:A Modest Multiband Antenna                                      725
NHC4:A Gain Antenna for 28 MHz                                       754
NHC5:Amateur Radio 101                                               776
NHC6:Such a Deal!                                                    789
NHC7:Over-the-Keyboard Desk Top                                      808

RADIO TIPS (RT)

RT1:The Trusty Slingshot                                             835

GENERAL INTEREST ARTICLES (GI)

GI1:Activating a Rare Island on CW: ZD9SXW                           847
GI2:Pacemakers, Interference and Amateur Radio                       872
GI3:Ham Radio in the Pacific at the End of WW II                     905
GI4:Wired for Wireless: Ted Rappaport, N9NB, and His Vision          924
GI5:LARC's Mode-S DXpedition                                         933
------------------------------------------------------------------------

TECHNICAL ARTICLES (TA)

Title>TA1:An SWR Detector Audio Adapter
Author>Spencer, Ben C. - G4YNM
Source>QST Jul 94, pp. 24-25
Abstract>Construction of a two-channel audible indicator that generates
tones proportional to unknown d.c. voltages; designed primarily for
use by blind hams to indicate forward and reverse power in SWR meters.

Digest>This construction project is the building of a dual voltage-
controlled audio oscillator, the output of which is two audible tones
with frequencies proportional to two d.c. voltages.  It is designed
primarily for use by blind hams to indicate the outputs of an SWR
detector, one channel for forward- and the other for reverse-power.  It
could be adapted to many other applications to indicate the approximate
measure of d.c. voltages, in whatever use.

A circuit diagram and parts list is included.  The circuit is simple;
it requires only three inexpensive ICs and a handful of electronic
components.  The two unknown voltages are amplified by half of a
dual op-amp IC, the amplified voltages feed voltage-controlled
oscillators which are the halves of a dual chip, and each audio output
is amplified by an op-amp that is the other side of the dual op-amp chip
previously described.  The audio outputs go to the two sides of a stereo
headphone jack.  Power requirements are a nominal 5-volts which can be
supplied by batteries, or other source.

The assembled circuit is so small that it will fit inside most SWR
detectors.  A single-sided PC-board is available from FAR Circuits,
18N640 Field Ct, Dundee, IL 60118-9269 for the price of $4.00, including
domestic shipping.  A PC-board template package is available from the
ARRL Technical Department for an SASE.  Address the request for the
Spencer Audible SWR Adapter template to Technical Department Secretary,
ARRL 225 Main St., Newington, CT 06111.
                               _________

Title>TA2:A Pocket-Size, Talking Morse Code Practice Computer
Author>Staton, Ken - KD6LHB
Source>QST Jul 94, pp. 26-28
Abstract>Building a portable code practice generator to produce random
audible morse signals.

Digest>This is a construction article for a random code generator that
produces morse code made up of random letters or letter groups at
controllable speed.  The finished unit is small, light weight, and can
be taken anywhere to provide code practice anytime a few free minutes
are available.

It is actually a special-purpose computer using an 8031 microcontroller
as its central processing unit (CPU).  The software is self-contained,
on a read-only memory chip (ROM).  The only external control is a single
push-button; the operator pushes it and the unit speaks a character in
return.  The characters form a verbal menu as follows: G,R,S,T,5,1,2,X.
Releasing the switch during or immediately after the voiced character
selects that option.  The options are:
        G = 5-character groups
        R = random characters
        S = sequential characters
        T = toggle speech on/off
        5 = Farnsworth 5-wpm (character rate: 16-wpm)
        1 = Farnsworth 13-wpm (character rate: 18-wpm)
        2 = Farnsworth 20-wpm (character rate: 23-wpm)
        X = Exit with no change of mode
To shut off the unit completely, one removes the headphone plug from its
jack.  The code practice computer generates random letters and, when in
the speech mode, speaks the letter immediately after it is sent.

Construction is straightforward.  It uses four logic chips, including
the CPU, a digital-to-analog converter, and E-Prom read-only memory, and
a generic logic chip.  In addition, it includes two analog chips: a dual
audio amplifier and a voltage-regulator.  Power is provided by an
integral 9-volt battery.

Partial or complete kits are available from the Staton Company,
Box 2601, El Granada, CA 94018.  The complete kit, excluding only
battery and enclosure, is $67.00, including shipping in North America.
A PC-board template package is available from the ARRL Technical
Department Secretary, 225 Main St., Newington, CT 06111.  Ask for the
Staton Code-Practice Computer template.
                               _________

Title>TA3:The Null Steerer Revisited
Author>Michaels, Charles J. - W7XC
Source>QST Jul 94, pp. 29-33
Abstract>Using phased primary and secondary antennas to null
interference during reception.

Digest>Null steering is a method of using a secondary antenna spaced
some distance from the main station antenna and combining the signals
received from the two phased in such a way as to suppress an interfering
signal.  The interference can be QRM or broadband noise from different
kinds of electrical sources.  The technique works best in suppressing
interference from local sources.  It is less effective on QRM from
greater distances.  For skywave signals, it is almost entirely
ineffective.

Mr. Michaels has developed an effective unit which is compact and easy
to build.  He finds that it wirjs very well, especially on the 40-, 80-,
and 160-meter bands.  He reports that he can put a 50-dB. null on a
nearby KW CW signal and that his Null Steerer is more valuable than all
the QRM and QRN suppressing features of his modern transceiver.

The unit uses internal phasing lines made of coils wound on toroidal
forms and resisters, along with an adjustable gain amplifier to balance
the amplitude of the cancelling signal.

The author built a 5-band model containing a 5-position, 5-pole rotary
switch for band switching.  It covers all 9 bands from 160- to
10-meters.  The 10-, 12-, 15-, and 17-meter bands are covered by one
filter, the next covers 20- and 30-meters, and the other filters cover
40-, 80-, and 160-meters respectively.  He also points out that a single
band model, simpler and less expensive, can be built.

Schematic diagrams and parts lists are included for the amplifier alone,
as well as for the overall system.  The amplifier is an untuned, broad
band unit using two monolithic microwave integrated circuits (MMICs)
that provides a nominal gain of up to 40-dB.  A PC-board for the
amplifier, only, is available from FAR Circuits, 18N640 Field Court,
Dundee, IL 60118-9269 for a price of $5.50, including domestic shipping.
Also a PCB template package is available from the ARRL Technical
Department Secretary.  Ask for the Michaels Null Steerer template.
                               _________

Title>TA4:144-MHz. Sporadic-E
Author>Pocock, Emil - W3EP
Source>QST Jul 94, pp. 37-41
Abstract>A statistical study of Sporadic-E propagation openings on
2-meters analyzed by season, time of day, and region.

Digest>Emil Pocock, the conductor of the monthly column THE WORLD ABOVE
50-MHz, has made a study of sporadic-E propagation as it appears on the
144-MHz. band.  Sporadic-E contacts occur most commonly on 6-meters, but
are often reported on 10- and 2-meters, as well.  They are most common
in May through August of each year, but occasionally occur in all
months.

It is clear that the effect occurs because of temporary ionized clouds
that appear in the E-layer about 100-km. (60-miles) above the earth and
reflect VHF signals extremely efficiently.  Contacts, when they occur,
are frequently very strong and relatively noise-free.

To obtain data from US amateur operations, the author gathered published
reports of 2-meter occurrences found in QST and in six VHF newsletters
from 1976 through 1993, and also consulted some 24 logs of stations
operated by hams very active on VHF.  The records included reports of
thousands of sporadic-E contacts, most over distances between 1000- and
2500-kilometers (600- to 1500-miles).

Additionally, European sources provided much useful data.  The English
publication, VHF-UHF DXer, published records covering openings in the
May-August seasons from 1977 to 1992.  Relevant data were also collected
from non-amateur sources.  Included were records concerning sporadic-E
propagation on 50- and 88-MHz. from a Texas source.

After compiling the data and eliminating records of contacts that might
not have been via sporadic-E, he ended with 209 specific openings on 161
different dates.  The article is an analysis of those data points.

When graphs were plotted of contacts made over the 14-year period, and
compared with a plot of solar flux, it appeared that sporadic-E
occurrences peak during the rising portion and falling portion of the
sunspot cycle, more frequently than at either the peak or the trough.
Consequently, there seems to be a 5- or 6-year cycle, although it has
only been observed for one of those "cycles", hence must be considered a
preliminary hypothesis to be tested in the future.

In more than 90-percent of all 2-meter openings in the USA, the centers
of the path between the stations have been located within one of four
areas.  He has classified these as Areas A, B, C, and D.  A is Colorado
and New Mexico; B is Kansas, Missouri, and Oklahoma; C extends from Ohio
and Indiana to the Florida panhandle and the Alabama-Mississippi Gulf
coast; D covers from West ***ia to South Carolina, between the coast
and the Appalachians.  No doubt the most important factor determining
this distribution is the population of active amateurs.  But, in
addition, there is probably a real effect that tends to promote the
conditions in the upper atmosphere over those areas that make it
favorable for E-layer ionization.

One conclusion that the author reached is that, without doubt, there are
a great number of sporadic-E openings that occur without being
discovered.  Active hams would do well to pay attention to conditions on
the FM broadcast band or the VHF television band, looking for
indications of distant stations appearing in enhanced strength, and
otherwise monitoring band conditions, especially during the "off season"
when most operators are discouraged from even listening.  They may
receive some very pleasant surprises!
                               _________

Title>TA5:Key Components of Modern Receiver Design - Part 3
Author>Rohde, Dr. Ulrich L. - KA2WEU
Source>QST Jul 94, pp. 42-45
Abstract>Comparison tests between current amateur receiver performance
and that of receivers built, or modified, in accordance with principles
described in earlier installments.

Digest>In this final installment, Dr. Rohde summarizes his discussion of
modern optimum circuit elements for modern HF receivers by describing
the performance of late models of popular amateur transceivers, and how
far from optimum it is.  His point is that, with little or no increase
in component cost, substantial improvements could be made, and no doubt
will be.

He describes a visit to Munich, Germany, where he put a short antenna
out the window of his 19th floor hotel room and listened to a Kenwood
TS-450S on the 40-meter band soon after sunset.  In scanning the entire
band he heard nothing but noise, the S-Meter never dropped below S-9,
and he did not recognize a single amateur signal.  When he switched to
20-meters, he found several "ghost" broadcast stations, that is signals
that apparently carry two different voice modulations.  When he switched
in 20-dB. of attenuation, the ghosts disappeared completely.  This poor
performance on both bands was the result of second-order intermodulation
distortion (IMD).

In Part 2, he indicated that replacing the switching diodes in the
front-end filter section with PIN diodes would make substantial
improvement.  To prove the point, he obtained a Yaesu FT-890, a Kenwood
TS-50, and an ICOM IC-765, all with PIN diode modifications.  With that
modification, and certain other ones outlined in the previous
installments, he found that all three receivers showed drastically
improved performance under crowded band conditions.

Finally, he made measurements on a current state-of-the-art,
professional transceiver which sells in the $18,000 range.  With this,
he established the best performance that can now be obtained when cost
is no object.  The comparison showed that making inexpensive
modifications to the current top-line transceivers can improve their
strong signal and AGC performance nearly to the level of the most
expensive equipment available.

In a side-bar with the article, Mark Wilson - AA2Z, the Editor of QST,
announced that, from now on, QST Product Reviews will include the
results of second-order IMD testing along with third-order.  No longer
will these deficiencies be swept under the rug!
------------------------------------------------------------------------

PRODUCT REVIEW (PR)
        Conductor: Mark Wilson - AA2Z
                   Editor, QST
                               _________

Title>PR1:ETP Alpha 89 Linear Power Amplifier
Author>Sumner, David - K1ZZ
Source>QST Jul 94, p. 76-77
Abstract>Evaluation of a top quality, conservatively designed amplifier.

Digest>The ETO Alpha 89 is one of the few commercial amplifiers that is
rated for full legal power output under all operating modes and
conditions on the HF bands.  It is big, heavy, and conservatively
designed.

The amplifier is not highly automated, and cannot be operated remotely
by computer control.  It still requires the operator to turn knobs in
tuning it to frequency!  However, it does the next best thing.  It has
an elaborate operation analysis and warning system that automatically
flashes lights to indicate any maladjustment and automatically shuts
down the power completely if it is so bad as to risk damage to the
equipment.  Variables that are monitored and which will set off alarms
include: total output (alarm over 1500-watts), grid current (yellow
above 85-ma. and red above 100 ma.), SWR (yellow above 1.5:1; red, with
total shutdown, above 2:1).

Mains power requirement is from 190- to 250-volts a.c., up to 20-amps.
The transformer is tapped for 200-, 220-, or 240-volts.  There is no
provision for operating it with lower line voltage.  The power tubes are
a pair of 3CX800A7 operated in parallel, grounded grid.  A front panel
switch, labelled SSB/CW, changes bias to operate Class B, for SSB, or
Class C, for CW.  Those who are not concerned about excess power
dissipation can operate on the SSB position in all modes.

The reviewer found the operation to be "smooth and solid".  The worst
case spectral display showed the third-order distortion product 42-dB.
below peak output, and the fifth-order is 45-dB. down, while operating
at 1.5 KW PEP at 14.0 MHz.

The manufacturer's suggested list price is $3495.  The apparatus, less
tubes, carries a 4-year warranty.  The tubes are warranted by the
manufacturer separately.
                               _________

Title>PR2:Radio Shack DSP Communication Noise Reduction System
Author>Kearman, Jim - KR1S
Source>QST Jul 94, pp. 78-79
Abstract>An inexpensive DSP unit.  Does well in eliminating heterodynes,
but is not very useful for noise-reduction nor general use in CW and SSB.

Digest>Radio Shack is offering a digital signal processor for receivers
at a list price of $80.  This is substantially lower than that of the
popular amateur-radio grade DSP filters, but its performance also falls
short of the popular ham models.

Unlike others on the market, this unit comes with a built-in audio
amplifier and loudspeaker.  It operates from a 12-volt d.c. supply and
draws up to 1.0 amp of supply current.

The unit acts as a variable bandwidth audio filter and also contains a tone
cancelling algorithm that, quite effectively, removes one or more
heterodynes from phone signals received.  But the filter bandwidths and
lack of adjustability of center frequency make them almost useless in CW
operation, and only marginally useful for SSB.

Although there are three filter modes that are stated to provide noise
reduction, Radio Shack has admitted that it does not contain a
noise-reduction algorithm!  The noise reduction that occurs in use is
only that which is inherent in the reduced bandwidth provided by the
filter.

The unit does do a good job of removing the multiple heterodynes
resulting from the proliferation of shortwave broadcasting stations on
the 40-meter band during evening hours.  It would be very useful for
shortwave listeners, and it seems obvious that this is the market that
was being targeted when Radio Shack established the operating
specifications for the product.
                               _________

Title>PR33:Willco Electronics ICM-1024 Memory Replacement Board
Author>Kearman, Jim - KR1S
Source>QST Jul 94, p. 79
Abstract>A replacement board that owners can install themselves when the
self-contained battery in ICOM models R-71, IC-745, or IC-751/751A
fails.

Digest>The ICOM R-71 receiver, the IC-745 or IC-751/751A transceivers
use a complex operating system held in volatile memory.  It is
maintained by a self-contained battery, but when that battery fails, the
entire unit stops operating.  Until now, the only solution has been to
return the unit to ICOM to be equipped with a new battery!

Willco Electronics, owned by Jack Albert - WA9FVP, provides a plug-in
circuit board that any ham can install on their own.  It is only
necessary to remove the bottom cover and replace the original memory
board with the ICM-1024.

In installing it in an IC-751/751A, it is also necessary to add a wire
jumper and remove a resistor on the new board before making the change.

The ICM-1024 board also contains a lithium battery to support the
on-board memory.  Owners can change this battery themselves.  Doing so
requires re-initializing the settings of the board, but it typically is
done only once about every five years.

The replacement board also greatly expands the number of memories
available in the transceiver.  When bought new, there were only 32 in
the transceiver.  The new board provides up to 1024 memories for anyone
who can think of how to use that many!

The ICM-1024 is available from the manufacturer at PO Box 788, New
Lenox, IL 60451.  Its list price is $150.00.
------------------------------------------------------------------------

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

Title>HK1:Improved Receive Performance for the Kenwood TS-450S/AT
        Transceiver
Author>DeCoons, David W. - KE2SL
Source>QST Jul 94, p. 80
Abstract>Describes a modification to utilize the antenna tuner in
receiving as well as transmitting.

Digest>In many cases in which an antenna tuner is used for transmitting,
receive performance might also benefit from its use.  Using it,
discrimination against adjacent-channel interference and the
second-order IMD dynamic range will be improved, as has been explained
by Dr. Rohde in his receiver articles in this and the two preceding
issues of QST.  But most transceivers with built-in antenna tuners use
the tuner only while transmitting.

Mr. DeCoons determined a method of modifying his TS-450S/AT so that the
tuner is always in the circuit.  In this article, he give step-by-step
instructions of how to do it.  In his description, he uses component
numbers, connection numbers, and the like, that are of meaning only to
those with a TS-450 manual in front of them.

He reports that he has noticed improvement of as much as 1 to 2 S-units
using the tuner.  He invites any reader who encounters any problems, or
has comments about this modification, to write to him.  His address is:
144 Page Ave., Lyndhurst, NJ 07071.
                               _________

Title>HK2:Silent Full Break-In Transceiver TR Switching for the
        Alpha 87a
Author>Jeutter, Dean C. - K3GGN
Source>QST Jul 94, pp. 80-81
Abstract>A simple, silent circuit to replace the noisy keying relay in
the Kenwood TS-850S transceiver.

Digest>The author uses his TS-850S transceiver to drive an Alpha 87A
amplifier, often using CW with full break-in.  He found the noise of the
transceiver's TR relay to be very annoying.  To quiet the sound, he
replaced the switching relay with an electronic circuit.  In this letter
he describes the circuit and the success he has had with it.

He uses a surface-mount dual MOSFET, the Si9955, with a single chip
resistor built on a tiny circuit board (5/8" x 1/2", or 16- x 13-mm.)
that he stuffs inside the TS-850's "Remote" DIN connector!  In the
TS-850S, the TR control signal is either 0-volts in "Receive" or
+12-volts d.c. in "Transmit".  The author uses that voltage as the power
supply to the interface.  When the it goes positive, the drain-to-source
resistance drops to a fraction of one ohm, effectively grounding the TR
input of the Alpha 87A and putting it into "Transmit".  A piece of small
diameter coax is used as the lead to the amplifier TR input.  The action
is silent and instantaneous.

If tiny construction is not necessary, the circuit could be duplicated
using any of many small switching MOSFETS and a conventional 1/4-watt
resistor in a small box.
                               _________

Title>HK3:Try Diversity Reception and Transmission
Author>Weber, Ralph L. - W8TYK
Source>QST Jul 94, p. 81
Abstract>Simulating diversity operation by paralleling two antennas in
both receiving and transmitting.

Digest>Diversity reception is commonly used in military and commercial
communication links in order to combat fading caused when a single
sky-wave signal arrives from slightly different directions and with
different polarization.  As the different paths fluctuate, the phase of
the arriving signals will shift enough to cause alternate constructive
and destructive interference.  Using two or more antennas physically
separated and/or in different polarization, and feeding each into a
separate receiver front end, then combining the audio, often provides
significant improvement of readability at a correspondingly greater
investment in equipment.

Mr. Weber has tried to approximate the same effect both in receiving and
in transmitting by combining two or more antennas into a common
feedline,   He uses a trap vertical and a 160-meter horizontal loop.
Both antennas are matched to 50-ohm coax, so to combine them he
paralleled the connectors to provide a 25-ohm load for his tuner to
match.

He reports: "It works great!"  He is both giving and getting better reports
from stations that he works on a regular basis.
                               _________

Title>HK4:Reduced Frequency Drift During CW Operation with the
        Ten-Tec Scout
Author>Broadwell, Chuck - W5UXH
Source>QST Jul 94, p. 81
Abstract>Sometimes with high-speed CW the Scout does not correct
frequency properly.  How to overcome the problem is described.

Digest>The Ten-Tec Scout does not use a digital synthesizer for
frequency determination.  Instead, it uses an analog VCO, the frequency
of which is automatically measured periodically and small corrections
made to keep it on frequency.  These corrections can only occur during
receiving, and sometimes high-speed CW does not allow enough time for
proper correction; consequently significant drifts or sudden frequency
shifts can occur.

Mr. Broadwell has discovered that, so long as he keys with an external
key, not using the internal keyer, he can "fool" the microprocessor so
that it "thinks" he is receiving and proceeds to make the frequent
adjustments necessary.  He describes, step-by-step, the changes that
must be made to specific wire numbers, and the like.

He reports that the modification has made a great improvement in his
frequency stability.  However, he also points out that one cannot use RIT
after the modification has been made.
------------------------------------------------------------------------

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

Title>Subject: MOVs
Author>Sandoz, Jim - N2MPT
Source>QST Jul 94, pp. 82-83
Abstract>MOVs provide protection against voltage surges.  They must be
used carefully.  Ways to use, and not to use, them are outlined.

Digest>Metal oxide varistors (MOVs) are effective devices for protecting
against high-voltage surges.  But if used wrongly they can, themselves,
be exceedingly dangerous.

An MOV is normally attached across the supply voltage of a circuit to be
protected; its function is to short out instantly any voltage higher than the
rated level that may occur.  But they are designed to protect against
short spikes, and cannot dissipate much power.  If the voltage rises to
a high level and continues, the MOV will quickly burn out and may
explode, splattering molten metal onto adjacent surfaces.

Mr. Sandoz cautions that the voltage threshold of the protective MOV
should always be at least 50-percent higher than the normal level to be
expected.  After the MOV shorts, if the line voltage remains high, the
only protection is in the circuit breaker or fuse in the line.  If one
should make the mistake of putting an MOV with a 130-volt a.c. rating
across a 120-volt line, it would be very likely that a surge of some
time duration would actuate the MOV.  The degree of protection will
depend upon the associated circuitry.  If the circuit being protected is
electronic, it is conceivable that the small-gauge wiring in the device
would limit the line current enough that the fuse would not blow!  The
result would be a nearly certain meltdown or fire with perhaps disastrous
results.

Another misuse that the author worries about occurs when people put MOVs
directly across telephone lines, hoping thereby to protect a modem.  If
a "line cross" should occur (when a power line falls across a telephone
line), several hundred volts may come in on the phone line.  But the
telephone wire is of such fine gauge that perhaps only 0.5 amp of
current will flow to ground through the MOV and the internal house
wiring, not enough to blow a fuse.  But that represents 250-watts if the
voltage is 500-volts and within one minute smoke may be rising from
locations throughout the house.

The author's advice is to avoid do-it-yourself protection and stay with
quality surge-protectors approved by appropriate agencies such as UL.
Finally, although protective devices can often be effective in the face
of surges induced by distant lightning, nothing will protect against a
direct lightning strike on antennas, power lines, or telephone lines
nearby.  The only protection for equipment in that event is to unplug
power lines, telephone lines, and antennas when the equipment is not in
use.                           _________

Title>TC2:North Shadow
Author>McNally, Irvin L. - K6WX
Source>QST Jul 94, p. 83
Abstract>Two ways to determine true north.  One uses the sun at noon,
the other Polaris.

Digest>Amateurs who are setting up antennas to track satellites have
need to determine precisely where north is.  Often they use plumb-bobs
to sight the North Star (Polaris).

The same rotation of the earth that gives the illusion that the sun
moves across the sky from east to west also makes the stars in the
northern sky appear to rotate in circles around a point in the sky
directly in line with the earth's polar axis, the celestial north pole.
Since Polaris is 1-degree away from that, it traces out a 2-degree
diameter circle.

It is directly north only when it crosses its "meridian transits", that
is when it appears to be directly below or directly above the pole in
the sky when seen from the earth.  To make use of Polaris and obtain
accuracy better than one degree, it is necessary to get data from the
NAUTICAL ALMANAC, or SKY AND TELESCOPE magazine, to determine when those
transits occur.

An easier way is, perhaps, to use the shadow of a vertical pole or plumb
bob at noon, local time.  This, however, requires one to take account of
the "Equation of Time", because the sun passes local meridian a few
minutes earlier or later than noon, local sun time, as the seasons
progress.  Mr. McNally has written a program in IBM Basic called
NSHADOW.BAS to determine the local time of the north shadow for any day
of the year.  One needs to enter only the precise local longitude, the
month, day, and one's local time zone.  The program can be downloaded
from the ARRL BBS (203) 666-0578, or on Internet, via ftp, to
oak.oakland.edu in file: /pub/hamradio/arrl/infoserver/qst.
------------------------------------------------------------------------

FEEDBACK (FB)

Title>FB1:"A Calibrated Noise Source for Amateur Radio", QST May 94
Author>Sabin, William - W0IYH
Source>QST Jul 94, p. 83
Abstract>Typographical errors.

Digest>Two typographical errors occur in the article.  On page 29,
equation 6, there should not be a second "=" sign between the numeral 1
and the "+" sign.  On page 40, equation 8, a minus 1 is missing.  It
should read:
        F(DUT) = F(TOT) - (F(NMI)-1))/G(DUT)
                               _________

Title>FB2:"Small High-Efficiency Loop Antennas", QST Jun 86, pp. 33-36
Author>Hart, Ted - W5QJR
Source>QST Jul 94, p. 83
Abstract>Correction of an error in Equation 2.

Digest>This article has recently been cited by John Belrose' article in
QST Nov 93: "An Update on Compact Transmitting Loop Antennas".  William
J. ("Bill") Orr, VE3CRN points out an error in Equation 2 of the 1986
article, which was mislabeled as "Equation 5".  Its correct form is:
        R(L) = 9.96 * 10^-4 * (SQRT(F)) * (S/D)
                               _________

Title>FB3:"Amateur Use of Telescoping Masts", QST May 94, pp. 41-45
Author>Haviland, R. P. - W4MB
Source>QST Jul 94, p.  83
Abstract>Correction of values in Table 1.

Digest>In Table 1, the MAX V LD for sections 2 through 5 are 3395, 2291,
1665, and 1088 lbs., respectively.
------------------------------------------------------------------------

NEW HAM COMPANION (NHC)
                               _________

Title>NHC1:The Doctor is IN
Author>Various
Source>QST Jul 94, p. 66
Abstract>Questions and answers.

Digest>Questions discussed this month include: how to listen to one's
own transmitter; the necessity of assuring correct FSK polarity in
digital modes; interconnections between Internet and Packet radio;
2-meter interference from adjacent-channel paging services; using a
couterpoise to eliminate difficult grounding problems; and use of
miscellaneous gutters, fences, or railings as antennas.
                               _________

Title>NHC2:Understanding Signal Strength
Author>Wilson, George - W1OLP
Source>QST Jul 94, p. 67
Abstract>Explanation of the logarithmic nature of signal strength
perception and measurement.

Digest>This is an explanation of the logarithmic nature of signal
strength and how it relates to power and S-meter indications.  Included
is an illustration showing four scales graduated in S-units, power
multipliers, and two versions of power in watts.

The original S-units were defined as a doubling of received signal
voltage, which represents a quadrupling of power received, thus each
change of one S-unit represents a 4:1 change of power.  After the
S-meter scale reaches S-9, the next graduations are typically
"+ 10-dB.", "+ 20-db.", and "+ 30-db."  In that area of the scale,
each graduation represents a power change of 10:1.

To illustrate the enormity of changes of transmitter power that would be
required to move the S-meter of a remote receiver over the full scale,
the author has labeled the other two scales in actual transmitted power.
One scale starts at S-2 with 0.01-watts.  On that basis, to drive it to
S-9 would require 160-watts; 10-dB. over S-9 would require 1.6-KW, and
to 30-dB. over S-9 would need 160-KW.  In another case, if a 50-watt
transmitter is only registering S-1 at the remote receiver, to increase
the signal to S-9 would require 3.3-million watts!
                               _________

Title>NHC3:A Modest Multi-Band Antenna
Author>Brogden, Al - K3KMO
Source>QST Jul 94, p. 68
Abstract>Describes a dipole half-inside, half-outside of the house.

Digest>The author describes a multiband dipole that he put up when he
recently moved into a new home.  He lives in a 3-story apartment
building and has access to the attic.  The building is more than 50-feet
(15-meters) long measured parallel with the gable, and there is a tree
more than 75-feet away, in line with the gable.  He wanted the dipole to
be 135-feet (41.15-meters) long, half on each side of center, so he put
the antenna half inside the attic and half outside the house.

He anchored the antenna in the tree with a rope of a proper length to
put the center insulator just outside the wall of the building, then ran
the rest of the wire through a hole in the attic wall for the full
length of the attic inside the roof.  He wanted to locate the center
insulator immediately outside the wall so that a twin-wire feeder could
easily pass through a window into his apartment close by.  This meant
that he had to fit some 67-feet of wire into the 50-foot long attic,
which he did by bending the last 17-feet at right angles inside the
attic.  The wire ended up about 40-feet (12-meters) above the ground,
half inside and half outside the wooden building.

He uses a Kenwood TS-50 with an antenna tuner and gets excellent results
on all bands from 80-meters to 10-.  He even gets creditable results on
160-meters.
                               _________

Title>NHC4:A Gain Antenna for 28-MHz.
Author>Beezley, Brian - K6STI
Source>QST Jul 94, p. 70
Abstract>Description of a very simple wire antenna that provides gain.

Digest>Described is a simple antenna for 10-meters that provides a
slight gain over a dipole when it is mounted with the top at least
30-feet (9-meters) high.  It is a rectangle made of wire; the width is
73-inches (1.85-meters) and the height of the rectangle is 146-inches
(3.71-meters).  It is fed in the center of the bottom leg with 50-ohm
coax.

At the feedpoint, the coax is split apart and the shield braid connected
to one end of the wire, the center conductor to the other.  Directly
below the feedpoint is a ***formed by winding three turns of the coax
into a coil, 1-foot (30-cm.) in diameter.

Calculated gain over real earth is 2.1-dBd.  No description is made of
how the wire is to be supported.
                               _________

Title>NHC5:Amateur Radio 101
Author>Hughes, Justin - KA1ULT
Source>QST Jul 94, pp. 71-72
Abstract>Operating 2-meters from a college dormitory room.

Digest>Mr. Hughes is a student at North Adams State College in
Massachusetts, living in a dormitory.  In his room, he keeps a 2-meter
station, using an indoor sleeve dipole that allows him to access a
nearby repeater.  With this setup, he is able to keep in contact with
his parents and friends all over western Massachusetts.
                               _________

Title>NHC6:Such a Deal!
Author>Ford, Steve - WB8IMY
Source>QST Jul 94, pp. 73-74
Abstract>Advice on maximizing sales in fleamarkets.

Digest>Hamfest fleamarkets are a fixture in ham radio and are sources of
pleasure and profit for a great many amateurs.  In this article, Mr.
Ford gives some advice for how sellers can maximize their sales and,
presumably, their profits.  He advises vendors to arrive early; to set up
displays before the crowd arrives; that equipment should be clean and
well displayed; sell ham or computer equipment only; have a chair to sit
in but don't sit in it much; be prepared for bad weather; try to have
a.c. power available for demonstration; try to get someone to help "mind
the store" so that you can get some breaks; be sure to have change in
small bills; and don't accept checks except from local buyers.  Finally,
be sure to obey the local laws regarding taxation.
                               _________

Title>NHC7:Over the Keyboard Desktop
Author>Leyson, Herbert E. - AA7XP
Source>QST Jul 94, p. 75
Abstract>Building a desktop for a ham operating position.

Digest>Mr. Leyson describes and illustrates with a drawing and
photograph a clever arrangement for the working surface of his radio
operating table/desk.  He operates digital modes and requires a keyboard
at his operating position, but also needs a flat writing surface.  He
realized that the optimum height for a keyboard is several inches lower
than that for a writing surface.

To accomodate his requirements while preserving a compact furniture
design, he built a working desk with a glass top for the writing surface
mounted 3-3/4" (84-mm.) above the wooden furniture top.  This allows him
to reach under the glass to operate the keyboard while still being able
to see the keys.  His glass top is made of 1/4" (6-mm.) thick tempered
glass, 42" wide (107-cm.) and 16-1/2" deep (42-cm.).  He runs a 1" x 2"
(25 x 50 mm.) wood brace underneath the glass in the long dimension
and also a 1/2" x 1/2" (13 x 13-mm.) strip with a 1/4" x 1/4"
(6 x 6-mm.) notch cut out of one corner along the front edge of the
glass.  He notes that, if half-inch (13-mm.) glass were used, the
additional supports would not be necessary.
------------------------------------------------------------------------

RADIO TIPS (RT)

Title>The Trusty Slingshot
Author>Ford, Steve - WB8IMY
Source>QST Jul 94, p. 70
Abstract>To get ropes over a top branch in a tall tree, use a slingshot.
Put a small fishing sinker on the end of a line, shoot it over the limb,
then use it to pull a rope up and over.
------------------------------------------------------------------------

GENERAL INTEREST ARTICLES (GI)
                               _________

Title>GI1:Activating a Rare Island on CW
Author>Western, Roger - G3SXW
Source>QST Jul 94, pp. 19-23
Abstract>A DXpedition to Tristan da Cunha.

Digest>This is a story of a DXpedition to what is, arguably, the most
isolated populated land on the face of the earth.  But it was not an
uncomfortable or dangerous expedition.

The destination was the island of Tristan da Cunha in the south-central
Atlantic Ocean.   A settled population of British people have lived on
the island for several generations, totaling about 300 people, and they
live comfortably with most modern conveniences.  However, there is no
airstrip and only two ships regularly visit the island per year.  One
stays only 48-hours, but the other brings all yearly supplies each
October and stays for three weeks.  The author booked passage on that
ship; lived with one of the islanders who is, himself, a ham; operated
for the three week stay; and returned with the ship to its home port in
Capetown, South Africa.

During his stay, he was given the call sign ZD9SXW, operated CW, and
operating alone made 23,213 contacts!
                               _________

Title>Pacemakers, Interference, and Amateur Radio
Author>Weber, M.D., Fred - AA2KI
Source>QST Jul 94, pp. 34-36
Abstract>Describes precautions necessary for amateurs who use
pacemakers.

Digest>Dr. Weber prepared this article to answer two questions: (1) Can
hams who use pacemakers safely pursue amateur radio? (2) If they can,
what safety precautions should they take?

Pacemakers are electronic timing devices that are surgically inserted
under the skin and a tiny wire lead passed through a vein into the heart
muscle, itself.  The electronics detect whether or not the patient's
nervous system is generating the proper pulses to cause the heart to
pump regularly.  If it misses one, the pacemaker supplies the
deficiency.  But the voltage levels are small, less than 1.0-volt, and
the leadwire inside the body is a potential antenna, so interference
from external fields is of concern.

The author points out that electronic pacemakers have been used since
1957 and are in very wide use now.  Included among the users are
substantial numbers of hams who have suffered no problems with them.
However, problems have occurred with heavy current and strong magnetic
field devices such as electric welders, electric utility substations,
and the like.  Patients wearing pacemakers must be aware of the
potential hazards and take precautions, but it is unlikely that the
electric or magnetic fields caused by even high power amateur stations
would cause much problem.   However, prudence would dictate that one
should not expose the body to an indoor antenna running high power, for
example, whether or not a pacemaker is in use.
                               _________

Title>GI3:Ham Radio in the Pacific at the End of WW II
Author>Veregge, E. C. "Bud" - W6PBI
Source>QST Jul 94, pp. 46-47
Abstract>Describes ham operations by a US marine ham in North China in
1945.

Digest>Shortly after the end of World War II, the author was in the U.S.
Marine Corps, stationed in northern China.  He was one of 16 hams in the
area who followed military procedures, were officially assigned
callsigns between XU1YA and XU1YZ, and legally began ham activities.
But they were greatly outnumbered by GI hams throughout Asia and the
western Pacific who had access to military radio gear and put it on the
air using callsigns out of their own imagination.

This is the story of how the author set up his station and some of the
QSOs that he had with others around half the world.
                               _________

Title>GI4:Wired for Wireless: Ted Rappaport, N9NB, and His Vision
Author>Cain, James D. - K1TN
Source>QST Jul 94, pp. 48-51
Abstract>Digest>A semi-biographical sketch of N9NB, who is a professor
at ***ia Tech, and the amateur activities of several of his friends
in the area.
                               _________

Title>GI5:LARC's Mode-S DXpedition
Author>Kelly, Jim - KK3K and Bledsoe, Don - WB6LYI
Source>QST Jul 94, pp. 52-53
Abstract>Describes a DXpedition to the Caribbean which included 2.4-GHz.
operation.

Digest>The Lambda Amateur Radio Club (LARC) is an active, worldwide
organization founded 20-years ago for gay and *** hams.  Among their
many activities, they have sponsored three successive yearly OSCAR
DXpeditions to Caribbean islands.

In the 1994 trip, they set up on Anguila from March 4 to 10 and included
equipment for Mode S (435-MHz. uplink, 2.4 GHz. downlink), the first
time from a Caribbean location.  Eight or more members participated.
This is the story of their success, and the enjoyment had by all.
------------------------------------------------------------------------