[CW] Spark and Continuous Wave History

[D.J.J. Ring, Jr.]

An experpt from Modern Radio Operation by J.O. Smith who operated Special
Amateur radio station 2ZL which was granted to him for use on the short
waves below 200 meters.  There is also an article on CW here
http://earlyradiohistory.us/1922smit.htm

He also the operator in this famous (infamous?) early radiotelephone
broadcast:  http://earlyradiohistory.us/century2.htm
Modern radio operation By James Owen Smith, 2ZL
http://books.google.com/books/download/Modern_radio_operation.pdf

Spark vs. Continuous Wave Transmission

A great many amateurs who have used the spark method of transmission for
many years have been known in the past to utterly refuse to be interested in
continuous wave transmission, and to give many reasons why C.W. transmission
would never supplant, or even equal, the old familiar spark method. It is a
notable and interesting fact also that after C.W. had been used a while by
others many of these same amateurs were the first to comment on the
readily-apparent advantages of it, especially its low decrement, or rather
lack of decrement, the amazing distances it would cover on small power and
its great flexibility.

In the case of the spark transmitter, employing alternating current of some
frequency, it is good for one thing—telegraphing. It has frequently been
stated that the only way to get anywhere with a spark set is to use power to
the limit. It is true that while his intentions are of the best, in many
cases the amateur is limited in a mechanical way in the construction of his
antenna and ground system and does the best he can instead of the best for
results. The writer has personally visited a great many amateur stations
throughout the country and in almost every case noted that the antenna and
ground system was entirely inadequate to handle properly the amount of
energy put into it by the spark transmitter. The necessity of designing the
transmitter and antenna system for each other is an important point
generally overlooked by amateurs.

If one were to attempt to use pressure and force two gallons of liquid into
a one-gallon receptacle, something would be likely to happen. In the case of
the station using a 1 K.W. spark transmitted on a *y± *K.W. antenna, the
something that happens is the emission of energy on a hundred or so wave
lengths, even with a loose coupling. The effect is the same as in the case
of a too ciosely coupled set—where energy is radiated over a wide band of
wave lengths.

The result, especially in congested localities, is readily apparent. About
75 per cent. of the amateur interference (QRM)- we hear so much about, is
due to the fact that energy is being radiated over a wide band of wave
lengths, instead of on a narrow band as it should. Certainly the receiver
can be tuned only to one wave length at a time, consequently all the energy
radiated on other wave lengths is wasted energy, accomplishing nothing but
interference with other stations that are endeavoring to receive on
neighboring wave lengths.

The legal decrement of a transmitting station is fixed at .2, and even
where, in a few cases, this feature of the radio law is complied with, there
is interference on other wave lengths when a nearby station is endeavoring
to receive signals. In the case of C.W. transmission, the energy is
practically all radiated on one wave length.

It will readily be seen that C.W. transmission eliminates practically all
the unnecessary interference caused by a spark set of reasonable power. The
fact that the signals from a C.W. transmitter can be heard at only one place
on the receiving set is one reason why many amateurs have objected to its
use as a means of communication. These objections are based on both ends of
the transaction:—the operator of the transmitting station experiences
difficulty in raising a distant station, unless the receiver of the station
happened to be set on the transmitting wave length, and the receiving
operator complains of the unusual sharpness of tuning the received signals,
which calls for more than ordinary care in the adjustment of circuits, etc.
These objections, however, seem trivial in the face of the great advantage
of C.W. transmission over the spark method, especially as they can be
overcome easily. As the power of C.W. transmitters gradually increases, as
will certainly
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be true in the future, there will be less difficulty in "raising"
practically any station within working range without resorting to previous
notice and agreement.

The complaint of sharpness of tuning at the receiving end usually dissipates
quicker than last week's salary once the advantages of it are experienced.
Once the signals from a C.W. transmitter are located, the possibilities of
tuning them away from QRM and QRN (interference and static) are there and it
is a simple matter to accomplish this very desirable result. It is quite a
common thing nowadays to get a card from some fellow hundreds of miles away
saying that the "C.W. signals were QSA (strong) and could be read through
local QRM," etc., without trouble. This is often true even when the antenna
input of the transmitting station was in the neighborhood of only 20 or 25
watts, and the antenna current approximately one ampere. On nights when the
air is "dead" and no distant spark stations can be heard, there is usually
some distant station using straight or unmodulated C.W. whose signals can be
easily read.

When the output of a C.W. set is modulated with a buzzer or tone wheel, the
received signal can be regenerated and amplified to a much greater extent
than a spark signal, especially of the 60-cycle variety. Another great
advantage in the use of C.W. by amateurs for short distance work
particularly is voice modulation. The fact that the law requires that work
shall be carried on with a minimum of power necessary to effect successful
communication is a point generally overlooked, intentionally or otherwise,
by many operators of 1 K.W. spark transmitters and it is a frequent
occurrence to hear a 1 K.W. station using full power to communicate with
another station on the next block. This phase of amateur radio has been
repeatedly criticised, more often by operators of spark coils and low
powered transmitting sets, than otherwise. Everyone is familiar with the
tales of the interfering spark coil station, whose operator is usually
accused of being able to transmit, but not receive, and the misuse of power
by the big station is a favorite method of counter-attack on the part of the
small station operator. It is, however, quite true, that the high-powered
amateur stations are frequently interrupted in relay work by small stations
and spend much precious time and use many K.W.'s of good energy trying to
make the operator of the small station understand that he is interfering—at
the end of which the operator of the small station often comes back and
informs the high-powered stations that his "signals are strong tonight."

The use of a voice modulated C.W. set obviates all such disputes. The
operator of the small station can usually understand English, even though he
never heard of Morse, and if he understands that he is creating interference
is usually entirely willing to "stand by" or "go to bed."

In the case of the spark transmitter of high power (1 K.W. or more) all
sorts of mechanical and electrical difficulties are generally present.
"Kickbacks" are the bugbear of an amateur's life. The matter of insulation
is another matter of great importance, both in the case of interior wiring
and the antenna system. It is generally possible to insulate interior wiring
properly without great trouble, but where high voltages are imposed upon an
antenna it is a different matter. Where more energy is impressed upon an
antenna system than the system can properly take care of brush discharges
occur to such an extent as to cause aerial fireworks of considerable
magnitude, resulting in a loss of efficiency. Frequently the antenna
insulators break down under such unusual strain and cause further losses and
trouble.

effective operation of the offending station, such occurrences certainly do
not add to the peace of mind of the operator.

With a C.W. set, however, unless the set is of unusually high power, the
pull on the service lines is so small as to make connection on the regular
house service lines entirely feasible and safe, and consequently no separate
service is necessary or required. Neither is there any danger of overloading
the antenna.

Unless the set is of very high power as amateur sets go, the difficulty is
liable to be in the other direction, in that the capacity of the antenna
system might be so great as to absorb energy faster than the set could
supply it. The result of such condition would be that the set would not
oscillate. Here, again, the rule that transmitters and antenna systems
should be designed for each other also holds good. In the case of C.W.
transmission, however, the matter is more favorable to the amateur field, in
that a smaller antenna system, involving less expenditure of money for
erection and upkeep, will answer every requirement of successful
transmission.

In view of the fact that practically all the energy of a C.W. transmitter is
radiated on one wave length, a low power set of such characteristics will
usually accomplish as much at the receiver as a spark transmitter of many
times the power, making a C.W. transmitter a comparatively inexpensive, safe
and wonderful method of communication.

==============================================================================================

So "Spark" as interesting as it sounded - just faded into history with much
more efficient (both in terms of reception, transmission and bandwidth) than
Continuous Wave.


73


 David J. Ring, Jr., N1EA <http://www.qsl.net/n1ea/>
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JARL-A1<http://a1club.net/>,
A1-OP <http://www.arrl.org/a-1-op>, ex-FOC 1271 ARRL-LM<http://www.arrl.org/>
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