March 1965 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
sunspot cycle in
1965 was at the same point as it is today - at a minimum (see chart) - so this article
is back in style. Sunspots affect high frequency (HF) radio wave
propagation in the Earth's ionosphere by generating greater ultraviolet (UV) and x-ray radiation
that affects the conductivity of the
E, and F layers. Although sunspots are cooler areas on the sun's surface, bordering them
which are actually brighter and emit higher levels of charged particles (plasma) that
also affect conductivity of the ionosphere's upper layers. Sunspots improve long distance
communications on some bands. A sunspot is distinctly different from a
mass ejection (CME), which is a chunk of highly charged plasma spewing out from a
If released in our direction, a CME can cause profound disturbances in the atmosphere
due to electron interaction with the Earth's magnetic field (aurorae are an accompanying
effect). Unlike CME's, a sunspot does not need to directly face the Earth to produce
an effect; if we can see it, it can affect us. CME's inhibit long distance communications
in most bands. Quantitative (measured) ionospheric science was at its infancy in 1965.
The International Geophysical Year (1957-1958) had as one of its primary
goals to commence a concentrated study of the upper atmosphere and its effects on radio
propagation. By no coincidence, Russia's
Sputnik and the
satellites were launched then, directly leading to the discovery of the
Allen radiation belt.
How the short-wave bands will be in March and April plus some information on the
poor conditions expected
During ionospheric storms the normal day-to-day structure of the reflecting
layers undergoes immense changes. Particles from the sunspots are caught in the earth's
magnetic field and find their way into the ionosphere. The F layer (responsible for most
long-distance radio communication) is weakened. Signals either pass through this layer
into space or are weakly reflected. The D layer absorbs an abnormal number of radio signals
passing through this region, further reducing signal strengths.
Sunspots, or explosions on the surface of the sun, are caused by factors
unknown to us at this time. These explosions release a shower of particles that have
been recorded by satellites launched specifically for this purpose. The particles do
not travel with the speed of light and seemingly take 20-30 hours to reach the earth.
Scientists refer to the spreading out of particle streams as a "garden hose" effect.
Severe ionospheric storms will occur in March.
The relative number of ionospheric storms varies according to the
month, or season of the year. It also varies with sunspot activity - more sunspots mean
more ionospheric storms. Ionospheric disturbances are more frequent during the equinox
due to the position of the earth in its orbital plane.
WWV Propagation Forecasts. To enable users of the ionosphere, SWL's
included, to keep track of the latest radio conditions, the Central Radio Propagation
Laboratory of the National Bureau of Standards issues short-term propagation forecasts
four times daily, at 0000, 0700, 1200, and 1800 EST. These forecasts give estimates of
radio quality over North Atlantic transmission paths, such as between London and the
eastern United States. However, the forecasts are generally applicable to other paths,
particularly during good propagation conditions.
Although these forecasts are revised every five to seven hours, they are repeated
every five minutes by NBS Station WWV, in International Morse Code, on 2.5, 5, 10, 15,
20, and 25 mc. Each forecast is broadcast unchanged until the regularly scheduled revision
The forecasts consist of a letter and number; the number is the forecast, while the
letter identifies the quality of radio-propagation conditions prevailing at the time
the forecast is issued. The numbers used have the following meanings: 1 - useless; 2
- very poor; 3 - poor; 4 - poor to fair; 5 - fair; 6 - fair to good; 7 - good; 8 - very
good; 9 - excellent.
The radio quality at the time the forecast is issued, based on the average quality
of conditions in the two hours preceding its issue, is identified as follows:
W - Warning. Disturbed conditions (quality 1, 2, 3, or 4) exist.
U - Unsettled. Quality 5.
N - Normal. Quality 6, 7, 8, or 9.
A typical forecast statement would be "U-6," which means that propagation conditions
are now unsettled but radio quality is expected to improve to "fair to good" (6) during
the period covered by the forecast.
By Stanley Leinwoll, Radio Propagation Editor
Major international short-wave broadcasting schedule changes will become effective
Saturday, March 6, at 2000 EST. Here is a summary of expected conditions in the high-frequency
bands for March and April.
11 Meters. Because of the low level of sunspot activity, ll-meter
signals cannot be propagated via sky wave during the spring season. None of the short-wave
broadcasters have scheduled transmissions in this band.
13 Meters. Activity in this band is ex-pected to be below winter
levels. Principal users will be the Voice of America and the BBG between the hours of
1000 and 1800 GMT (0500-1300 EST). Interesting DX possibilities in this band include
Ghana on 21,530 kc. between 0900 and 1100 EST, Aus-tralia' on 21,540 kc. from about 2000
EST, and Pakistan on 21,590 kc. between 0500 and 0900 EST.
16 Meters. Fairly good DX'ing should be possible throughout much
of the day. Considerable use of this band will be made by the Europeans from early morning
to shortly after noon, EST. Ecuador, on 17,890 kc., is about the only Latin-American
country scheduled to broadcast in this band, and the best time for reception is around
1500 EST. Congo, on 17,720 kc., during the period from 0800 to 1000 EST, is another attractive
19 Meters. This band will be most pro-ductive for DX during the daylight
hours, from very early morning to evening, with reception from all parts of the world
pos-sible at some time during the period when the band is open. During the morning hours
until mid-afternoon (EST), for example, reception should be good from Europe, Africa,
the Near East, and Latin America. During the late afternoon and evening, re-ception will
improve from Asia and Aus-tralia, and continue from Latin America.
25 Meters. Conditions in this band will improve over those observed
during the winter, when DX to many parts of the world was relatively poor. In the spring,
the ionosphere begins to stabilize-usable night-time frequencies get higher, while optimum
daytime frequencies get lower. This sea-sonal trend makes the 25-meter band useful for
longer periods of time. In general, re-ception from Europe, the Middle East, and Africa
should be possible during middle to late afternoon, local time. During the eve-ning hours,
the Latins will be predominant, while best DX possibilities from the Pacific should exist
during the morning hours.
31 Meters. The seasonal trend toward higher usable nighttime frequencies
will re-sult in improved conditions in this band. Reception from Europe, Asia, and Africa
should be possible from mid-afternoon into the evening hours, when South and Central
American stations will dominate. During the mid-morning hours, reception of sta-tions
to the west will be best. Among the better DX possibilities in this band are Ku-wait
on 9520 kc., Guinea on 9650 kc., Senegal on 9720 kc., and Israel on 9725 kc., all during
the afternoon hours, EST.
41 and 49 Meters. These bands will open up for DX reception during
the late after-noon hours, local time, and will remain open from one area of the world
or another throughout the night. Although interference levels will not be quite as bad
as they were during the past winter, they will neverthe-less be serious enough to hamper
many of the better DX catches. Some stations, how-ever, should be exceptionally strong
during the late evening hours. In general, DX re-ception should begin during the afternoon
from stations in Europe, the Middle East, Asia, and Africa. The distant Latins will start
coming in shortly afterward. For the late night DX'ers, signals from the east will start
going out several hours before dawn. Stations from the Pacific should be heard at this
time, and should continue to be heard until several hours after sunrise.
60 and 90 Meters. Conditions will deteri-orate in the spring. During
the past winter, the combination of low sunspot activity and a record number of users
made DX reception in these bands the best in history. With the approach of summer, static
levels will increase and signals will grow weaker. However, there will still be a few
good DX openings during the hours of darkness.
Standard Broadcast Band. The record-breaking DX conditions observed
during the winter months have come to an end. Sig-nals in the standard broadcast band
are growing weaker, and noise levels are in-creasing. This trend should continue as the
season progresses, nights grow shorter, and maximum usable frequencies increase. Good
DX will still be possible, but for shorter periods of time, and not nearly to the extent
observed in December and January.
Long-Wave Band. Some interest has been expressed in reception of
signals in the long-wave band, between 150 and 285 kc. The Geneva Radio Regulations of
1959 allocate this band to AM broadcasting in Europe, Africa, and part of Asia. Long-wave
broad-casting is fairly popular in Europe, although not as popular as medium-wave (or
what we call "standard") broadcasts.
In general, long-wave propagation is similar to medium-wave propagation: conditions
at night are much better than during the day, and propagation in winter months is better
than in the summer. One problem with reception of long-wave broadcasts that is more serious
than in any other part of the spectrum is the type of antenna required. Wavelengths in
the kilocycle range are extremely long, being on the order of about one mile at 180 kc.
This means that a simple half-wave dipole antenna would have to be half a mile long at
this frequency to be effective. Listeners cannot be expected to erect such antennas,
so a fairly long wire must do, which means a loss of signal strength. This fact - coupled
with the fact that as we go down in frequency, static levels and absorption in the ionosphere
increase - results in reception that is generally inferior to that in the medium-wave
Ionospheric Storms. From time to time disturbances occur in the upper
atmosphere which tend to disrupt long-distance communications by severely upsetting the
stability of the ionosphere. Such disturbances are most likely to occur during the spring
and fall equinox - March and April, and September and October - when the earth passes
through the plane of the sun's equator. They fall into two general categories: the ionospheric
storm and the sudden ionospheric disturbance (SID). Ionospheric storms usually develop
gradually and continue from several days to almost a week. The SID, on the other hand,
commences suddenly, and seldom lasts more than an hour.
Although they are different in nature, both disturbances have the same effect on communications:
during storms, signal levels fall off sharply, fading becomes se-vere, and the general
quality of DX reception deteriorates. During extreme conditions, a radio blackout may
occur during which it becomes impossible to maintain high-frequency communication with
many areas of the world.
During the early days of radio (the 1920's), it was not unusual for SWL's and amateurs
to rip their receivers apart during radio blackouts because they thought something had
gone wrong with the sets. Nowadays, we know better. Ionospheric storms are caused by
bursts of radiation from the sun. This radiation, composed of either extremely intense
ultraviolet radiation, or subatomic particles from an explosion on the sun, or both,
saturated the ionosphere, resulting in a tremendous increase in radio-wave absorption,
which in turn results in a sharp decrease in signal levels.
Posted March 7, 2018