Digest of Articles - QST Feb 94 (Long - 51k)

Digest of Articles - QST Feb 94 (Long - 51k)

Post by W. E. Van Hor » Wed, 06 Jul 1994 20:00:13

DIGEST OF ARTICLES - QST February, 1994

Following are digests of articles printed in the February, 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 Easy-to-Build 25-Watt MF/HF Amplifier                         70
TA2:Revisiting the RF Ammeter                                       112
TA3:Stacking Tribanders: A Super Station - Sorta                    167
TA4:The QSOcorder                                                   250

PRODUCT REVIEW (PR)

PR1:QST Compares: SSB Electronic UEK-2000S and Down East Microwave  304
        SHF-2400 2.4 GHz Satellite Downconverters
PR2:JPS Communications NRF-7 and NF-60 DSP Audio Filters            398

HINTS AND KINKS (HK)

HK1:Connecting Tape-Recorder Audio to the Kenwood TH-27 Hand-Held   483
        Transceiver
HK2:Be Sure to Clean and Exercise Plugs and Connectors              498
HK3:Hear Better With the Heil BM-10 Boomset                         514
HK4:Car-Engine Heater Keeps Rotator Lubricant Flowing               532
HK5:Curing RFI in a Digital Voice Recorder                          546
HK6:Holes Make Soldering Sponge Work Better                         566
HK7:Curing a Glitch in the N)HPK Low-Cost Frequency Counter         580

TECHNICAL CORRESPONDENCE (TC)

TC1:Correlating Solar Flux and Sunspots                             602
TC2:Mininec Bugs: K6STI Plays Exterminator                          624
TC3:More on the Si8901/SD8901                                       652

FEEDBACK (FB)

FB1:"Computer Controlled Electronic Test Equipment - Part 1 -       673
        QST Dec 93
FB2:"An Inexpensive SSTV System" - QST Jan 93                       682

NEW HAM COMPANION (NHC)

NHC1:Working Satellite RS-12 - The Ultimate Satellite Primer        695
NHC2:Building Your Own Station Accessories                          759
NHC3:The Doctor is IN                                               813
NHC4:DXing With 2-Meter Packet Mail                                 828

RADIO TIPS (RT)

RT1:An Abbreviated Packet-Speak Glossary                            866

GENERAL INTEREST ARTICLES (GI)

GI1:California's Burning                                            898
GI2:Camel Trophy '93                                                933
------------------------------------------------------------------------

TECHNICAL ARTICLES (TC)
                               _________

Title>TA1:An Easy-To-Build 25-Watt MF/HF Amplifier
Author>Breed, Gary - K9AY
Source>QST Feb 94, pp. 31-34
Abstract>Building a 25- or 50-watt amplifier from only a single
integrated module plus a few passive components.

Digest>Modern electronic components involving various levels of
integration make electronic construction substantially less complex.
Mr. Breed has achieved almost the ultimate level of construction
simplicity in his r.f. amplifier.  In this article, he explains how to
build a complete 25- or 50-watt power amplifier for use on any band from
1.8 MHz. to 30 MHz. using nothing but two r.f. transformers, a linear
amplifier module, and a few bypass capacitors!

The resulting amplifier is untuned and broadband.  It is band-switched
only to select one of seven low-pass filter networks to suppress
harmonics more than 50-dB. below the fundamental.  A separate filter is
used for each of the 80-, 40-, 30-, and 20-meter bands; 15- and
17-meters share a filter, as does 10- and 12-meters.

The transistors in the module are JFETs and operate in Class A, so they
are extremely linear.  Class A operation has one drawback, however; its
efficiency is low, no more than 40 percent.  This means that 60 percent
of the d.c. power must be dissipated in the transistors as heat and so
an extra-large heat sink is built onto the back of the amplifier
cabinet.  To reduce the power loss when the amplifier is not
transmitting, a send\receive relay applies near-cutoff bias to the
transistors in the "Receive" position.

The low-pass filters are 5-section Chebyshev circuits, each utilizing
two inductors and three capacitors.  The author designed the filters
using a computer program that is in the public domain.  The inductors
are wound with either Number 26 or 22 wire on toroidal cores and
standard capacitor values are used in all cases.

Parts kits, including all electronic and mechanical components excepting
only an enclosure, connectors, and relay, are available from Crestone
Engineering, Box 3702, Littleton, CO 80161.  A 25-watt kit is priced at
$121, and the 50-watt kit at $196, including USA shipping.
                               _________

Title>TA2:Revisiting the R.F. Ammeter
Author>Stanley, John - K4ERO
Source>QST Feb 94, pp. 35-37
Abstract>Types of R.F. Ammeters and amateur uses of them.

Digest>R.F. ammeters were commonly used in the early days of radio and
through the 1930's, but have been displaced in amateur work by
directional wattmeters in most ham stations today.  They are commonly
used in commercial radio stations, however, even now.

Modern r.f. ammeters are almost all of the thermocouple type.  The
current passes through a non-inductive resistor where it generates heat,
and the temperature rise is measured with a thermocouple.  Since the
heat generated is proportional to the square of the current, the scale
of the instrument is a non-linear "square-law" scale on which the
numbers are farther apart at the high end and squeezed together at the
low end.

Thermocouples, for those who are not familiar with them, are
commonly-used devices for measuring temperature in industrial
applications.  An almost absurdly simple device, a thermocouple is made
of two pieces of wire, of equal length but dissimilar metals, welded
together at one end, (the "hot junction").  When the temperature at the
welded end is different from that at the unwelded end, (the "cold
junction"), a voltage will develop at the open end.  The voltage is
small, measured in millivolts, but is a precise measure of the
temperature difference between ends.  The wires can be of any gauge,
hence it can be made a very tiny device.

Attaching a thermocouple to the resistor through which the unknown r.f.
current flows, and measuring the voltage developed, creates an r.f.
ammeter.  It has one great advantage over any other type of r.f. current
instrument: it can be calibrated using d.c. and the calibration remains
the same for a.c. at frequencies from 50 Hz. all the way to VHF.

In a side-bar accompanying the article, the author points out that r.f.
ammeters are available FREE to purchasers of Duracel (R) batteries!  The
packages in which these are now being sold contains a battery tester
which is, in fact, a 3- to 5- ohm resistor attached to a liquid-crystal
temperature detector.  When the two ends of the resistor are squeezed
onto the terminals of a good 1.5-volt battery, the current flow causes
enough temperature rise that the liquid crystal turns color from the one
end almost all the way to the other.

A used battery, with reduced voltage will cause the strip to turn color
only part-way, and a totally dead battery will cause no color change, at
all.  During testing, the current flow through the resistor is of the
order of 0.2- to 0.4-amps.  That same resistor can be used to get a
relative measure of r.f. current of the same magnitudes.  If higher
currents are to be measured, the range can be increased by attaching
other resistors in parallel.  One could hardly ask for a more
inexpensive instrument!
                               _________

Title>TA3:Stacking Tribanders: A Super Station - Sorta
Author>Straw, R. Dean - N6BV/1 and Hopengarten, Fred - K1VR
Source>QST Feb 94, pp. 38-44
Abstract>Analysis of stacked triband beams.  They provide most of the
benefits given by multiple stacks of monoband beams at a fraction of the
cost.

Digest>Many of the "Big Gun" stations that populate the top of the lists
of contest winners use multiple high towers with stacked yagi antennas.
The authors of this article make a convincing case that stacked
tribanders can be used to produce results nearly as good, with much less
complexity, cost, and long-term maintenance requirements.

When a triband antenna which operates on 10-, 15-, and 20-meters is
stacked with a similar one a given distance apart, the stacking distance
in terms of wavelength is quite different from band-to-band.  But
contrary to the impression of many hams, the authors point out that
there are no "magic" stacking distances.  Performance increases smoothly
starting from zero and increasing to a full wavelength, or more.

Computer calculations of antenna gain over flat ground of two different
stacks on all three bands were made and the article contains elevation
angle plots of both stacks on the three bands.  The first stack was made
up of three Hy-Gain TH7DX tribanders at 30-, 60-, and 90-foot (9.1-,
18.3-, and 27.4-meter) elevations.  The second stack was two similar
antennas at 40- and 70-feet (12.2- and 21.3-meters).  In addition, a
single tribander at 70-feet and another at 40-feet are plotted on all
bands and a single dipole at 90-feet on 10-meters only.

Several striking facts are apparent from the plots.  First, there is
very little difference between the stack of three antennas and that of
the two antennas.  At 5-degrees elevation angle, where low-angle
radiation is most important for multi-hop, long-range DX, the difference
is only about 2-dB.; but the 3-stack antenna has nearly 10-dB. gain over
the dipole at the height of the highest beam.

Another is the fact that any antenna or assembly of antennas, whether it
be a stack of beams, a single beam, or a single dipole, shows a null at
some particular elevation angle.  For the stacks, the main lobe of
radiation is broader and so the null is at a higher angle than is the
case for any single antenna.  But in the case of either of the stacks on
any of the three bands, there are one or more nulls.  Consequently, it
is clearly an advantage to switch to using only one of the stacked
antennas to provide communications at a particular angle that happens to
fall within the null of the stack as a whole.

A table is presented showing the range of elevation angles for
communications between New England and Western Europe, and another for
New England to Eastern Europe, at each of the HF bands over the entire
sunspot cycle.  The data show that for the path to Western Europe, which
may sometimes be single hop, the elevation angles range from a minimum
of about 3- to 5-degrees and maximum of about 14- to 17-degrees.  To
Eastern Europe, which is most certainly multi-hop, the angles range from
about 1- to 13-degrees.

The basic effect of stacking is to concentrate the energy which, in a
single antenna would be radiated at high elevation angles where it is
primarily wasted, into the lower angles where it is effective for
communications.  Both of the stacks analyzed radiate over a wider range
of angles of elevation than any single antenna.  Hence, the major
benefit of the stack is the ability to cover a wider range of angles
than would otherwise be available.  In doing so, the added energy that
was "squeezed down" from the high angles manifests itself in a stronger
signal, hence higher gain.

Another benefit from stacked antennas is that, in reception, stacks are
much less affected by fading.  Even selective fading is often
dramatically reduced.  The cause of this effect is not entirely clear,
but it seems likely that the elimination of reception from the higher
angles may play a major part.  If, for example, signals are being
received from both low and high angles simultaneously, the phase shift
that would result from the one path being longer could result in
alternating destructive and constructive fading.

In the remainder of the article, the authors give a detailed description
of the antenna system at N6BV/1 in Windham, NH, and also describe an
"elegant approach to matching" used at K1VR which features a 50- to
25-ohm "un-un" using coils wound of RG-59A around type T-200A powdered
iron cores.  The K1VR array also utilizes 0.75-inch (19 mm.) hardline
for feed.
                               _________

Title>TA4:The QSOcorder
Author>Reyer, Steven E. - WA9VNJ
Source>QST Feb 94, pp. 45-48
Abstract>Construction an electronic device that records and replays, on
demand, the last ten seconds of the signal being monitored.

Digest>The QSOcorder is a device that allows one to replay the previous
few seconds of a signal being received.  It is easy to understand how
useful this would be in a QSO on either phone or CW.  Especially in a
contest or a DX pileup, very often one letter of a call sign is missed
or a momentary distortion leaves one uncertain of what was said.  Often,
replaying the same few seconds one or more times clears up the
uncertainty.

The author presents construction information for building the unit.  It
is all electronic and acts like an endless-loop tape recorder which at
all times is holding a record of the last ten seconds of audio received.
On the front panel there are two pushbuttons labeled "Long" and "Short".
Pressing the "Short" button replays the last five seconds; the "Long"
button plays the last ten.  As long as either button is held down, it
repeats again and again.  When the button is released, the signal
instantly returns to real time.  Alternatively, instead of operating in
the Automatic mode, there is a Manual mode in which the unit waits for
the "Record" switch to be actuated, whereupon it records 10 seconds and
holds it for replay as many times as desired.

A block diagram of the circuit shows that audio input passes through a
buffer amplifier and a low-pass filter with 3 KHz. cutoff.  Next, it
goes to an AD7569 audio I/O port where the signal is sampled and the
samples are converted to 8-bit digital form.  From there they move into
storage in two 32k-byte RAM chips.  When replay is called for, the
samples flow into the "heart of the system", an 8748H microcontroller
chip.  It is programmed in assembly language to select the digital
record, restore it to analog form, and pass it on through audio
amplifiers to an LM380 integrated audio amplifier.

A complete kit of parts for building the system, less only cabinet,
power supply, cables, and connectors, is available from the author for a
price of $102 including shipment in the USA and Canada.  Orders may be
sent to Reyer and Associates, P.O Box 17821, Milwaukee, WI 53217.  For
those who want to build the system from scratch, the author makes the
software available for non-commercial use for a price of $25.  A
PC-board template package is available free of charge from the ARRL.
Address a request to Reyer QSOcorder PC-board Template Package, ARRL
Technical Department Secretary, 225 Main Street, Newington, CT 06111,
including a business-size SASE.
------------------------------------------------------------------------

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

Title>PR1:QST Compares: SSB Electronic UEK-2000S and Down East
        Microwave SHF-2400 2.4 GHz. Satellite Down-Converters
Author>Ford, Steve - WB8IMY
Source>QST Feb 94, pp. 69-71
Abstract>Down-converters are the simplest and cheapest way for most hams
to get on microwave bands.  The reviewed models are good performers.

Digest>Satellite operations have suddenly made the 2.4-GHz. band
popular.  Hams have been having a great time working DX on Oscar 13,
primarily on Mode B (uplink on 70-cms., downlink on 2-meters).  But
2-meters is getting too crowded in many areas and QRM is ruining
satellite reception.  Consequently, many satellite enthusiasts are
moving to Mode S (uplink on 70-cms., downlink on 2.4 GHz.).

The 2.4-GHz. band has several advantages: noise levels are low, QRM is
rare, and antennas are very small.  A 2- or 3-foot (61- or 91-cm.) dish
gives marvelous reception and helical or Yagi antennas are very easy to
build and manipulate at these frequencies.

One disadvantage is that solid-dielectric coax transmission lines have
far too much loss to be practical for more than a few inches.  The
easiest solution to that problem is to use a down-converter mounted
right at the antenna to convert the signals to 2-meters.  This review
reports on the performance of two suitable units.

SSB Electronic UEK-2000S

The SSB Electronic UEK-2000S is a high-performance unit built using
state-of-the-art components and construction techniques.  The final
package is only slightly larger than a pack of cigarettes.

It uses a low-noise HEMT front end, a helical filter, a GaAs FET preamp,
and Schottky diode double-balanced mixer.  The Model UEK-2000SAT is
packaged in a weather-proof enclosure for mounting at the antenna.

The 2.4-GHz. band actually stretches from 2.4- to 2.45-GHz., a bandwidth
of 50-MHz.!  When this is converted to 2-meters, it is far too broad for
most 2-meter receiver to cover.  Fortunately, satellite operation is
confined to "only" 1-MHz. bandwidth, which is well within normal
coverage of 2-meter radios.

The manufacturer's specifications state a conversion gain of 17 dB. and
a noise figure of 0.8 dB.  Tests made in the ARRL lab showed that the
reviewed unit nicely surpasses both of these specs.  For operational
tests, the reviewer began with a 40-element loop-Yagi antenna that
worked, but not very well, because it is not circularly polarized as is
recommended.  Next, he tried a 3-foot parabolic dish using a crude feed
scheme copied from an article by G3RUH in a recent AMSAT JOURNAL.  It
worked so well on an outside mount that he decided to try it from inside
his shack; he found the results were still adequate for satisfactory
reception of a variety of QSOs.

The manufacturer's list price on the UEK-2000SAT is $399.95.  With an
extra amplifier that provides 30 dB. of conversion gain, the list is
$439.95.

Down East Microwave SHF-2400

Down East Microwave in Troy, Maine is offering, as a less-expensive
alternative, a down-converter with or without a low-noise preamplifier,
and either assembled or as a kit of parts.  The kit can be assembled
readily, and when completed is immediately ready for operation; no test
equipment or tune-up is required.  Its physical size is a bit more than
twice as large as the SSB Electronic unit.

The unit reviewed was purchased fully assembled.  The supplied case is
not weather-proof.

The manufacturer's specifications call for conversion gain of 16 dB. and
a noise figure of 5-dB without the preamplifier.  The ARRL lab test of
a unit bought assembled indicated that both specs were surpassed.

The reviewer used the same two antennas that he had used for the earlier
tests.  He again found that he could get only weak signals using the
loop Yagi but that reception using the dish was more than adequate for
listening to any QSOs that were on the satellite.

The reviewer states that whether or not the optional preamplifier is
required will depend upon the antenna with which the unit is used.  He
recommends that a buyer try it first without the preamplifier and add it
later if it is found to be required.  He did not state whether the unit
he tested was or was not so equipped.

If the cable run from the antenna and converter to the 2-meter receiver
is greater than 100 feet (30-meters), reception will benefit from the
addition of a booster amplifier.  The documentation that comes with the
kit includes a schematic for a suitable amplifier.

The manufacturer's list prices for the unit without preamp is $255
assembled or $155 for the kit.  The optional preamplifier, which comes
assembled, is $130.
                               _________

Title>PR2:JPS Communications NRF-7 and NF-60 DSP Audio Filters
Author>Rus Healy - NJ2L
Source>QST Feb 94, pp. 71-73
Abstract>Reviews two new DSP units: The Model NF-60 eliminates
heterodynes in the passband.  The NRF-7 is multi-mode; it eliminates
heterodynes and/or provides a selection of bandpass filters of
different widths.

Digest>JPS Communications, which has established a name for its digital
signal processing (DSP) filters, is now offering two additional models.

NF-60

The first is the NF-60 which provides notch filters to block out
heterodynes.  Characteristic of the DSP process, it will simultaneously
block out more than one heterodyne, if they are in the passband.

The ham community is becoming more aware that DSP "notch" filters are
quite different from any such that have been available before.   A DSP
filter does not notch out a fixed portion of the audio spectrum; in
fact, it does not "notch" at all.  In a sense, it "cancels out" the
heterodynes that appear, without blanking any significant portion of a
broad audio signal, such as voice, that is also present.  The NF-60 is a
single-purpose unit that does not perform any functions other than
heterodyne elimination.

The manufacturer's specifications call for a frequency response of
300-Hz. to 2.7-KHz, input to output delay of zero milliseconds, and a
notch depth of greater than 50 dB. for one to four tones.  The ARRL
laboratory tests indicated that these specs were almost met, except in
one rather unimportant respect.  That is, the frequency response is
actually broader at the low end: from 100 Hz. to 2.7-KHz.

The input-to-output delay measured 1.2 milliseconds which differs from
the spec by an insignificant amount.   The notch depth measured 60-dB.,
deeper than specified; however, tests showed that the depth of tone
suppression is a function of the strength of the signal.   Weak
heterodynes are suppressed less than strong ones, but that is not really
a disadvantage.  The final result is that all heterodynes are reduced to
a very low level.

The reviewer found that use of the unit makes an enormous difference
when operating in the 40-meter phone band after dark, when foreign
broadcast stations are so common.  The manufacturer's list price for the
NF-60 is $150.

NRF-7

The NRF-7 is a multi-mode DSP filter that provides 10 different
operating modes, switch-selectable.  One of the modes provides multiple
notches, very similar to those given by the NF-60.  Four more modes are
wide and narrow bandwidth filters for both SSB and CW.  The CW filters
have 250- and 500-Hz. and the SSB 1.5-KHz. and 2.1-KHz. widths
respectively.

Another selection is a "Data" filter with a 500-Hz. bandwidth centered
at 2.2 KHz. which is optimum for RTTY, AMTOR, PACTOR, and Packet.  The
next two switch positions provide wide and narrow SSB filters combined
with the notch function.

There is a "Peak" mode, useful in both SSB and CW reception, that reduces
the bandwidth adaptively in accordance with receiving conditions.  If
there is only one signal in the i.f. passband, the audio passband
will be narrowed to form a peak response only at the audio frequencies
of the signal so that the surrounding noise is greatly reduced.

The last mode combines "Peak" with "Notch" which provides almost a
"squelch" effect that quiets noise under key-up conditions.  The
manufacturer's list price on the NRF-7 is $250.

To complete the article, the author reminds readers that any audio
filter, including the reviewed DSP filters, is outside the receiver's
AGC loop.  If there are strong signals within the i.f. passband but not
in the audio passband, the operator will frequently find that an
interfering signal that s/he cannot hear is reducing the receiver gain
sufficiently to interfere with a weak signal being received.  The point
is that audio filters can supplement, but not supplant, i.f. filters.
------------------------------------------------------------------------

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

Title>HK1:Connecting Tape-Recorder Audio to the Kenwood TH-27
        Hand-Held Transceiver
Author>Crenshaw, Gerry - WD4BIS
Source>QST Feb 94, p. 74
Abstract>Constructing a switching network to route audio signals.

Digest>Mr. Crenshaw is the Net Control for the Garland, TX ARC
Information Net and uses his HT to play news bulletins for the net.  To
make this easy and convenient to do, he assembled three jacks, two
switches, and some parts inside a small metal box, then attached two
connectors to be plugged into the HT speaker jack and mike jack,
respectively.  A wiring diagram is included showing all details.
                               _________

Title>HK2:Be Sure to Clean and Exercise Plugs and Connectors
Author>Rainville, Henry - K2HG
Source>QST Feb 94, pp. 74-75
Abstract>When troubleshooting, do not neglect possible problems from
dirty or corroded connectors.

Digest>The author recently had the experience of finding his Kenwood
TS-440S go dead.  After finding the fuse to be still good, he found that
13.8 volt power was not getting into the rig.  The cause was corrosion
on the contacts of the power connector from the power supply to the rig.

He solved the problem by spraying the connectors pins and sockets with
contact cleaner, then plugged and unplugged it several times.
                               _________

Title>HK3:Hear Better With Heil BM-10 Boomset
Author>Thomas, Nick - N1KCZ
Source>QST Feb 94, p. 75
Abstract>Do not let ear-cushions muffle high frequencies.

Digest>Mr. Thomas, a former recording engineeer, discovered that the
foam ear-cushions on the Heil headset tend to muffle the higher
frequencies.  The solution is to cut a hole in the sponge of the
cushion.

He took a quarter-dollar coin, placed it in the center of the cushion,
and drew a circle around it with a ball-point pen.  Then he carefully
cut that size hole.  The result was greatly improved audibility of
frequencies above about 1000 Hz., substantially increasing the
intelligibility of certain received signals.
                               _________

Title>HK4:Car-Engine Heater Keeps Rotator Lubricant Flowing
Author>Mollentine, Richard - WA0KKC
Source>QST Feb 94, p. 75
Abstract>Keep lubricant warm during severe winter conditions.

Digest>The author's antenna rotator lubricant is rated for operation
"only" down to minus 20-degrees Fahrenheit (minus 29-degrees Celsius).
When the temperature dropped well below that last winter, he found that
his antenna would not move.  He solved the problem by attaching an
electrical car-engine heater to the bottom of the rotator mounting
plate for use during cold periods.
                               _________

Title>HK5:Curing RFI in a Digital Voice Recorder
Author>Clark, Bill - KB0AUK
Source>QST Feb 94, p. 75
Abstract>Ferrite line chokes on connecting cables eliminate r.f.
feedback.

Digest>Mr. Clark built the Digital Voice Recorder described in QST Dec
91: "The ChipTalker".  He found the recorded audio to be of poor quality
and, in addition, abnormalities occurred in transmit/receive switching.
He discovered the cause of both problems to be r.f. feedback getting
into the recorder.

He stopped the feedback by using Radio Shack clamp-on ferrite line
filters on the ends of the recorder mike-input and output cables, and
grounded his mike ground line to chassis ground on the back of the
recorder.  Then he ran a short wire from that grounding point to his
other station ground line.  Since then, he has had no further problems.
                               _________

Title>HK6:Holes Make Soldering Sponge Work Better
Author>Trigilio, Dan - KF6MU
Source>QST Feb 94, p. 75
Abstract>Cut holes in sponge wiper to help keep the soldering iron
clean.

Digest>Mr. Trigilio finds it easier to wipe his soldering iron on a
sponge if there are holes in the sponge so that the solder and dirt fall
through the holes during tip cleaning.  He buys his sponges in dry,
compressed form and finds it much easier to cut holes in the dry sponge
than after it has been wetted and expanded to normal size.
                               _________

Title>HK7:Curing a Glitch in the N0HPK Low-Cost Frequency Counter
Author>Agsten, Mike - WA8TXT
Source>QST Feb 94, p. 75
Abstract>Solution of a problem in counter described in QST Feb 89.

Digest>The subject frequency counter was described by Bainbridge in QST
Feb 89, pp. 21-26 "A Low-Cost Frequency Counter".  It uses a number of
counter chips, CD4017.  He discovered that some 4017's that work well at
other points in the circuit failed to work as "U2" in the schematic
diagram.  He found the cause to be that they were switching too fast,
causing an output pulse-width too narrow to clock the following chip,
U3.  He solved the problem by adding a 27 pf. capacitor from pins number
5 and 15 (jumpered together) to ground.  This "stretched" the pulse
sufficiently to provide reliable service.
------------------------------------------------------------------------

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

Title>TC1:Correlating Solar Flux and Sunspots
Author>Hall, Jerry - K1TD
Source>QST Feb 94, p. 76
Abstract>Adjust flux measurements for varying Sun-Earth distances.

Digest>In his letter, Mr. Hall explains that solar flux measurements,
made daily and reported hourly on WWV, must be normalized to remove the
effect of the varying distance between the earth and the sun before the
data are analyzed.  The earth is closest to the sun on January 3 and
farthest from it on July 4, each year.  If the radiation from the sun
were constant, the measure would be 7-percent greater on January 3 than
on July 4.  An appropriate multiplication factor is applied to the raw
measurements to prevent that factor from upsetting the calculations.

At the end of his letter he reports that, as of January, 1994, we are
about two-thirds of the way down the declining side of sunspot cycle No.
22 which began in September, 1986 and passed through maximum in July,
1989.  The cycle is forecast to end with minimum solar activity sometime
in late 1995 or early 1996.
                               _________

Title>TC2:Mininec Bugs: K6STI Plays Exterminator
Author>Beezley, Brian - K6STI
Source>QST Feb 94, p. 76
Abstract>Correction to the Mininec source code to eliminate two bugs.

Digest>Mr. Beezley, well-known supplier of antenna-analysis software,
reports that he has discovered two bugs in the Mininec program.  The
more serious bug causes incorrect radiation patterns for antenna models
with grounded wires.  It can cause the gain at low elevation angles to
be overstated by as much as several dB.  It only occurs with models in
which the wires are connected to imperfect ground; it does not affect
models using perfect ground or ungrounded wires.

He advises that one can check any Mininec-based program for this bug by
modeling a quarter-wave monopole over imperfect ground and calculating
the response at zero-degrees elevation.  There should be none!
Uncorrected programs will show a significant response unless one uses an
unusually large number of segments.  He goes on to state the specific
line numbers in the government-developed Mininec original program which
are in error.

The second Mininec bug occurs only with sloping, grounded wires in the
X-Y plane.  Since that geometry is seldom used, the bug is seldom
encountered.  Nevertheless, he gives the changes to be made to two
specific lines in the program to eliminate it.
                               _________

Title>TC3:More on the Si8901/SD8901
Author>Carver, Bill - K6OLG/7
Source>QST Feb 94, p. 77
Abstract>Improvement of the Makhinson Receiver described in QST Feb 93.

Digest>This letter is additional commentary regarding the Makhinson
article in QST Feb 93: "A High-Dynamic-Range MF/HF Receiver Front End".
Mr. Carver reports that he has built several Si8901 mixers and used them
in 40-, 20-, and 15-meter receivers.  From his experience, he makes two
suggestions: (1) Use a 74AC74 instead of the 74HC74 because its
switching times are extremely fast and it toggles at 150 MHz. (2)
Increase the square-wave amplitude.  A schematic diagram is included
with the letter.  He reports that this change reduces mixer conversion
loss by more than one dB., and the input intercept measured 46 dBm!

Mr. Carver also adds a response to a letter from Mal Crawford, in QST
Sep 93, pp. 79-80.
------------------------------------------------------------------------

FEEDBACK (FB)

Title>FB1:"Computer-Controlled Electronic Test Equipment - Part 1" -
        QST Dec 93
Author>Portugal, Ron
Source>QST Feb 94, p. 77
Abstract>In Figure 3, p. 45, in the upper-right-hand corner box, the
text should read: "NOTE: PINS 26 ON...", not "NOTE: PIN 6".
                               _________

Title>FB2:"An Inexpensive SSTV System" - QST Jan 93
Author>Vester, Ben - K3BC
Source>QST Feb 94, p. 77
Abstract>Correction of pin-identification in Figure 1

Digest>Mr. Vester advises that there was an error in the
pin-identification number in Figure 1.  The transmit-output line should
connect to the RTS line of J1  (Pin 7 for a DB9 connector, pin 4 for a
DB25 connector), not pin 8 (pin 5), as shown.
------------------------------------------------------------------------

NEW HAM COMPANION (NHC)

Title>NHC1:Working Satellite RS-12 - The Ultimate Satellite Primer
Author>Capon, Robert - WA3ULH
Source>QST Feb 94, pp. 58-60
Abstract>How to use RS-12, which requires only HF gear.

Digest>Satellite RS-12, launched by Russia in February, 1991, is the
only amateur satellite in which both the uplink and the downlink are at
HF.  Consequently, most hams with modern HF transceivers can work it
without buying new equipment.  This article describes how.

The RS-12 carries a linear transponder.  This means that it receives
signals between 21,210 and 21,250 KHz. and retransmits them on 29,410 to
29,450 KHz.  Since the 15-meter frequencies are in the advanced- or
extra-class bands, there is a special frequency set aside for novice-,
technician-, and general-class licensees at 21,129 KHz. and 29,454 KHz.

To operate with RS-12, the first thing to do is to find when the
satellite will be within range of your location.  The article contains a
locator table and a correction table which allow one to calculate when
the satellite will be within range of any location in the USA.  They are
good for the entire year 1994.

Second, listen for the satellite.  It contains a beacon that
continuously transmits a CW signal at about 20 wpm, giving information
about the status of the equipment aboard, on 29,408 KHz. plus or minus
2 KHz.

Step three is to listen to QSOs on the satellite.  Set the receiver to
SSB mode and scan the downlink band from 29,410 to 29,450 KHz.  You
should hear both SSB and CW signals.  Listen to the signals and note the
Doppler shift; the frequency of any one signal will slowly shift over
about 2 KHz. during a complete pass overhead.

Step four.  If you have only a single transceiver, skip this step.  If
you have a separate transmitter and receiver, or two transceivers,
listen to your own signal.  Set the transmitter to 21,230 KHz. and the
receiver to 29,430 KHz., then key a Morse "V" repeatedly while you tune
your receiver plus and minus 2 KHz. to hear them.

Step five.  If you are operating with one transceiver, set VFO "A" to
21,230 KHz. and get ready to transmit in SSB.  Set BFO "B" to 29,430
KHz., use the receive mode, and set the rig to split operation.  Listen
to be sure the frequency is not in use; if it is QSY up or down the
bands, keeping the last two digits of the frequencies the same.  Listen
for a "CQ", and respond normally.

If you have only General, Technician Plus, or Novice priveleges,
transmit CW on 21,129 KHz. and receive on 29,454 KHz.  This is the
frequency of the Robot repeater which can only handle one signal at a
time.  Listen first to be sure the Robot is not in use before
transmitting.

At first, don't be too concerned with Doppler shift, just keep the
transmissions short.  After gaining some experience, you can try
adjusting the transmitter frequency for progressive Doppler shifts.

Finally, after you have been successful with SSB, the author recommends
trying CW, which is his favorite mode for satellite operation.  If you
become "hooked" on satellite operation, he also recommends that you join
AMSAT, get a satellite-tracking program for your computer, and buy a
copy of the SATELLITE EXPERIMENTER'S HANDBOOK, published by ARRL.
                               _________

Title>NHC2:Building Your Own Station Accessories
Author>Gold, Jeff - AC4HF
Source>QST Feb 94, pp. 61-64
Abstract>Assembling kits SWR/power meter, keyer, antenna tuner, etc.

Digest>Mr. Gold is a self-confessed enthusiast for building his own
equipment and gets a great deal of pleasure from it.  He makes a
persuasive case that this is a good way to enhance one's enjoyment of
amateur radio, and save money, besides.

A good way to get started is to undertake relatively small-scale
projects and build station accessories from kits available from several
reliable sources.  He has built an SWR/power meter, a keyer, an antenna
tuner, and a DSP audio filter, among other things.

He recommends a QRP wattmeter kit sold by Oak Hills Research, 20879
Madison St., Big Rapids, MI 49307.  The finished unit measures forward
and reflected power over the range of 1-milliwatt to 10-watts.

Second, he has had excellent experience with C. M. Howes Communications
kits, imported from the U.K. by Townsend Electronics, Box 415,
Pierceton, IN 46562.  They have a large line of kits and he has built
several of their station accessories.  He recommends their SWR/power
meter that covers bands from 160- to 2-meters.  It measures SWR while
running from 1- to 30-watts and will measure power up to 100-watts.  The
kit sells for $24.95.

Mr. Gold has recently built an HF frequency counter from a kit sold by S
and S Engineering.  With a 4-digit display, it costs $49.95.  Adding 4
more digits costs an additional $16.95.

His keyer is the famous CMOS Super Keyer II that was featured in QST Nov
1990.  Anyone who works the CW bands in the USA knows how popular that
unit has been!  He bought the circuit board and parts kit from Idiom
Press, Box 583, Deerfield, IL 60015, for about $50.

Apparently not satisfied with only one keyer, Mr. Gold reports his
experiences building three others, supplied by Oak Hills Research, Tejas
R.F. Technology, Box 720331, Houston, TX 77272-0331, and the Howes ST-2,
bought from Townsend.

Next the author tells his experiences with audio filters, which
culminated in construction of the W9GR DSP filter that was described in
QST, September, 1992.  The first low cost, multiple-mode DSP filter
offered for amateur use, it took the ham world by storm.  It makes
striking improvement in reception of all kinds of HF signals, running
the gamut from CW, SSB, RTTY, AMTOR, etc.  The kit is offered for $125
by Quantics, Box 2163, Nevada City, CA 95959-2163.

Finally, he built antenna tuners from C. M. Howes, and also from Kanga
US, c/o Bill Kelsey, 3521 Spring Lake Drive, Findlay, OH 45840.
                               _________

Title>NHC3:The Doctor is IN
Author>Various
Source>QST Sep 93, p. 67
Abstract>Questions and answers of interest to newcomers to ham radio.

Digest:This month, the questions discussed regard how to test a balun;
the problems of using vertical antennas for short range communication;
noise caused by a TV horizontal sweep oscillator being picked up by a
ten-meter beam antenna; operating an HT with the battery-charger
connected; problems with r.f. feedback into the d.c. power supply; and
RFI getting into a lawn-sprinkler controller which caused the sprinkler
to come on.
                               _________

Title>NHC4:DXing with 2-Meter Packet Mail
Author>Smith, Presley - N5VGC
Source>QST Feb 94, pp. 66-68
Abstract>How to begin in 2-meter packet operations.

Digest>This article begins with a primer on how to get started in
2-meter packet operations.  It then describes the process of calling CQ
on packet and exchanging mail with other hams, including DX.

The first step in getting started is to sign-in with a local Packet
Bulletin Board System (PBBS).  From that point on, your "mailbox" where
messages addressed to you will arrive, is that PBBS, and its call
letters are your packet mail address.

Next, you command the PBBS to send to you a list of every message that
has "CQ" in the address field.  Compose replies to one or more that
catch your eye.  Then wait for an answer, which may require days, or
even weeks.  If you are impatient, or do not find a CQ that e***s your
interest, try a CQ message of your own.

Another approach to finding DX hams to correspond with is to monitor the
World Wide Packet Pals Directory, prepared by Ray Harkins, KB6LQV.  This
directory is sent over packet in several parts and gives name, QTH, call
sign of both home and PBBS, age, hobbies, and remarks.  Anyone who has
listed his/her name in the directory is asking for messages from others
and very likely will respond to one from you.

The article ends with specific instructions concerning how to compose a
packet message and a number of things that it should contain.
------------------------------------------------------------------------

RADIO TIPS (RT)

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

Title>RT1:An Abbreviated Packet-Speak Glossary
Author>Ford, Steve - WB8IMY
Source>QST Feb 94, p. 68
Abstract>Glossary of common terms used in packet operation.

Digest>This "tip" is printed as a side-bar with the article about DX on
2-meter packet.  It lists a few words that have special meaning in
packet operations:

Alias - Exactly like a nick-name.  It can be used as an address for a
        personal mailbox on a PBBS.

Download - Receiving files or messages from others on packet.

Gateway - A Node or BBS that is a link to a different communications
        system.  Examples are: to link 2-meter packet with HF packet;
        or to link packet to Internet.

Node - A junction point where data is relayed to other stations.

SSID - Secondary station identifier.  A number tacked onto a callsign to
       identify a different function, e.g. WB8IMY-2 may be a node and
       WB8IMY-4 may be a mailbox.

TNC - Terminal Node Controller.  An electronic device that processes
        data and controls transmission or reception of data in packets.

Upload - Sending files or messages to another packet station.
------------------------------------------------------------------------

GENERAL INTEREST ARTICLES (GI)

Title>GI1:California's Burning
Author>Palm, Rick - K1CE
Source>QST Feb 94, pp. 23-28
Abstract>Amateur involvement during brush fires in Southern California.

Digest>In October and November, 1993, the most devastating brush fires
in history raged in southern California.  Twenty-six separate fires
broke out in a two-week period, overwhelming the fire-fighting and
emergency facilities of the entire area.

As usual, amateur radio operators, organized in the Amateur Radio
Emergency Service (ARES), and Radio Amateur Civil Emergency Service
(RACES), provide much-needed communications support.

The article contains detailed accounts of the activities in Ventura
County, where 64 volunteers logged over 550 hours of service during
the four-day period from October 26 to 30.  After a very brief respite,
fires again broke out on November 2 and developed seemingly at about
twice the speed of the week before.  In the four days until late on
Saturday, November 6, 128 volunteers worked over 1100 hours.  Actually,
that total is understated because, in the press of the emergency, a
number of other ham volunteers' work was not recorded.

Similar stories describe the activities in the Conejo Valley area, in
the Marre and San Marcos, and in Orange County.  In Riverside County,
during the second week, four fires occurred and more than two dozen hams
worked under the supervision of the Emergency Operating Centers at
Riverside and Indio; also covered was the Fire Department's Emergency
Command Center.  San Diego hams also were called into service, both in
their own county and to help out in Orange County.  More than 117
amateurs were either directly involved, or on standby, during the
emergencies.
                               _________

Title>GI2:Camel Trophy '93
Author>Diamond, Richard - G4CVI
Source>QST Feb 94, pp. 29-30
Abstract>Story of a race through jungles of Borneo driving Land Rovers.

Digest>The Camel Trophy is a yearly race which, in 1993, was held in
Sabah, a province of Malaysia, located on the northwestern tip of the
island of Borneo.  It was an off-road adventure expedition that covered
more than 1000 miles of jungle along tracks and trails, sometimes
almost non-existent.

Six*** 2-man teams competed, all driving Land Rover Discoveries.  The
competitors were accompanied by a number of special-purpose vehicles
equipped for rafting, video, medical support, and other functions.

The race began and ended at the capital of Kota Kinabalu, and a
very well-equipped communications center was established at the
expedition headquarters, located in a resort hotel there.  All
communications were handled by a team from Britain, called the South
Midlands Communications Team headed by Richard Diamond, G4CVI, along
with Richard Mumford, G8SVC, Mike Deveraux, G3SED, Andy Cook, G4PIQ, and
Adrian Collins (no amateur call).  They were equipped with an 80-foot
(24-meter) high telescoping tower, mounted on a trailer, multi-band
rotary beams on ham bands as well as commercial frequencies, and they
erected dipoles for all ham bands from 10- to 160-meters and several
commercial frequencies.  A communications truck, equipped with two Yaesu
FT-757s and a satellite communications terminal, including a dish
antenna on a pneumatic lift, accompanied the racers and provided
communications back to the home base in Kota Kinabalu.

At the headquarters, one hotel room was equipped as the communications
room.  Their commercial communications operated on four assigned
frequencies and used two Yaesu FT-1000 transceivers, one equipped with
an Alpha 86 amplifier, as their main links.  The ham station used a
Yaesu FT-990 with a Tokyo High-Power HL1K amplifier on HF, and a Yaesu
FT-650 on 6-meters.  The 20-foot (6-meter) mast atop the 80-foot tower
carried a 6-element 6-meter Yagi and a 3-element tribander for ham use,
along with a second tribander designed for 11/15/20 MHz. commercial
frequencies.

In addition to handling all commercial communications, the operators had
time to make a great many amateur contacts.  They found 15-meters open
to Europe about 3-hours per day and 20-meters around 4-hours a day.
Forty and eighty meters opened for short periods.  The path to the USA
West Coast opened several evenings and a very few East Coast stations
were also heard.

All-in-all, they logged about 1000 6-meter QSOs and 5000 HF contacts.
In 1994, the race will be conducted through parts of Argentina,
Paraguay, and Chile from the end of March through May 7.
------------------------------------------------------------------------