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October 1947 QST
 Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
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"It is anybody's guess as to what modulation
system the amateur of 1975 will be using." That forward-looking line appeared in
this 1947 QST magazine infomercial by the National Company. The writers
probably had no real idea how different electronics would be 25 years in the future,
especially since
John Bardeen et al would not invent the transistor until two more
months (December 1947) after the publication of this issue. In their traditional
style, this full-page advertisement was heavy on text and light on images. The company
invested in customer education with the hope being a well-informed and appreciative
hobbyist would reward them with patronage.
National Company Advertisement
 Radiotelephone communication used to be so simple
when all we had to contend with was amplitude modulation or A.M., plus unintentional
F.M. when the oscillator happened to be unstable. But now, just keeping abreast
of some of the new modulation techniques is a major project. It is anybody's guess
as to what modulation system the amateur of 1975 will be using.
The amateur might well wander how same of these newer communication techniques,
such as Narrow Band Frequency Modulation, Narrow Band Phase Modulation, Frequency
Shift Telegraphy, Pulse Time Modulation, Pulse Count or Pulse Code Modulation, Pulse
Amplitude Modulation, Pulse Frequency Modulation, and Pulse Width Modulation will
change the D.X. or V.H.F. picture. Will they complicate or simplify the apparatus
involved? This is the stage of the game where predictions of things to come are
many, and differ widely. Basically, there are some fundamental facts which can be
applied to give a clearer understanding of the situation.
Concerning A.M., F.M. and P.M., as the unmodulated carrier at the receiver becomes
weaker it finally gets lost in the noise at a level governed by selectivity, and
all three systems are equal in this respect. When the carrier is modulated it becomes
readily apparent that the effectiveness of any one of these three systems far weak
signal reception is determined by its ability to combat noise.
A little investigation into the characteristics of noise shows that with tube
hiss and thermal noise, the noise reaches an average value, but noise peaks or very
short pulses are as much as 13 decibels (approximately) above the average level.
Ignition noise and man-made static are of this character but often have a much larger
ratio of peak-to-average value. As the R.F. signal level decreases toward the average
noise level these noise peaks obliterate the R.F. signal for very short intervals
of time and no type of modulation can be effective. Improvement in reception under
these circumstances can then be obtained by techniques which will permit the receiver
to. recover more rapidly after each paralyzing pulse of noise. If one system of
modulation permits receiver designs which allow the receiver to recover more rapidly
than another, that system will ultimately be superior in providing readability from
a weak signal.
Many practical factors enter the situation, such as complication or simplification
of receiver or transmitter, cost of parts, bandwidth to be used, and last, but not
least, reduction of broadcast interference, for a few examples.
The F.C.C. in its recent order allowing narrow-band F.M. and P.M. within amateur
phone bands for a one year period clearly indicates its desire to gather data on
practical operating experience. National, developing components and producing equipments,
will continue its efforts to help the amateur improve the art of radio. communication,
and will have an announcement of interest to N.B.F.M. experimenters.
The years have shown the amateur to be truly progressive and we expect to see
"N.B.F.M. given a real tryout between now and August 1, 1948.
W. A. Ready
Here are all the National Company advertisements I have:
- National's Company:
Merry Christmas and Happy New Year, January 1941
- National Company:
Noise Limiters, September 1950
- National Company: Modulators, April
1942
- National Company: Switches,
May 1939
- National Company: TMS Condenser, March 1939
- National Company: TVI, October
1953
- National Company:
Amateur Radio Activity, December 1952
- National Company: HRO-50
Receiver, May 1951
- National Company:
Noise Limiters, September 1950
- National
Company: Modulation, October 1947
- National Company:
Merry Christmas and Happy New Year, January 1942
- National Company:
Merry Christmas and Happy New Year, January 1941
- National Company: Switches,
May 1939
- National Company: AC Power Strip,
April 1939
- National Company: TMS Condenser,
March 1939
- National Company Catalog: NC80X
/ NC81X Receiver Advertisement, September 1937
- National Company:
IF Circuits, September 1935
Posted May 13, 2022
(updated from original post on 9/5/2016)
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