
SHORTWAVE RADIO
continued from page
73
source -frequencies, it has
continued
to solve
problems. Although disputes
have sometimes
been heated and bit-
ter, the participants have realized that
failure to compromise could lead to
the collapse
of the organization,
which would
be detrimental to all the
members.
It's surprising
that
similar groups,
operating regionally,
have
not
yet
emerged. For
example, a
Far Eastern
'FCC,
coordinating frequencies
around the Pacific rim, would
cer-
tainly improve the situation in that
area
of
the
world.
Anyone wanting
a free copy of a
recent coordinated schedule, which
consists of 32 pages of material,
should write
to Shirley Sandler, RFE/
RL Inc., 1775
Broadway, New York,
NY
10019.
Shortwave conditions
As the
days lengthen in March and
April, the higher frequencies will
re-
main open for DX
longer than during
the
winter
months. During the day in
the east, 15 MHz, 17
MHz, 21 MHz,
and 26 MHz
will
be
possible from
early morning
until several hours after
sunset. The
amateur 100 -meter
band
will
open to Europe,
and
openings
to
South America
and Africa
will
also
occur regularly;
in the late afternoon,
trans
-Pacific
10 -meter openings will
occur.
During
the evening and nighttime
hours, good
to excellent DX will
be
possible in
all bands from 6 MHz
to 15
MHz,
depending upon the location of
the transmitting station; moreover,
17
MHz
will
be open,
especially from
Africa and Latin America.
Due
to approaching summer
condi-
tions, noise
levels in
the broadcast
band
will
begin to increase,
making
DX more
difficult than it
has been.
During
years of high sunspot
ac-
tivity the number
of severe
ionospheric storms increases.
As a
result, radio
conditions periodically
become very
poor. Disturbed
condi-
tions tend
to
peak
during the equinox
months
of March and
September. Ma-
jor storms
can black out virtually
the
entire
shortwave
spectrum for
a day or
two at a time. In
the early days of
radio, many
listeners and radio
ama-
teurs
dismantled their radios
looking
for bugs
that
weren't
there. R -E
LETTERS
continued from page
15
full voltage
will be
dumped
across
the
remaining
capacitor(s),
which
will also fail.
C1
16µF
400V
C2
16µF
2o0Ú
71,
RI
400K
w
R2
200K
v.
w
FIG. 1
Usually a resistive divider of
suitable
wattage, with resistance
proportional to the WVDC of the
capacitors, and whose total
value
will allow
a current
flow of approxi-
mately 1 mA, will protect the ca-
pacitors from that mode of
failure.
(See Fig. 1.) The nominal values
would
be
1
KO
per volt
and
0.001
x
the
resistance in KSI wattage.
I
enjoy your
magazine a great
deal. It is
always
full of all kinds of
interesting
stories, projects,
and
technology updates.
VIC SCHMIDTMANN
Newark,
CA
ACTIVE ANTENNA
In
the
article "Active Antenna"
(Radio
-Electronics, February 1989),
Fig.
2, which
shows Q1 FET,
MPF102,
would lead
you to believe
that the middle lead is
the gate. Of
FIG. 2
course, it isn't; it is the
source (or
"S "). The
photograph,
Fig.
3 of the
article, bears that out. It shows
MPF102
to be twisted -if you look
very
closely.
My
drawing (Fig. 2) is correct.
JOHN L. KURSCHNER
Toms
River, NJ
R -E
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