Family Harmonics

Amateurs could anticipate at least some of the effects of the recently concluded 1927 Washington Convention that would occur in the coming year. Call signs would be changed, and nations around the world would allocate bands adhering to the convention’s guidelines.

Most importantly, there was about to be a rush by commercial interests to claim new frequencies in the short waves.1 The newly freed portions of former amateur bands would be in highest demand since they had not previously been available—specifically 7,300–8,000 and 14,400–16,000 kHz. Six months early, the FRC was already issuing construction permits for commercial stations in those windows using approximately 30-kHz spacing at 40 meters and 60-kHz spacing at 20 meters, continuing their practice of assuming a wider channel width was necessary in direct proportion to the operating frequency.

Amateurs therefore could expect to begin hearing non-amateur incursions into the current bands as 1928 drew to a close. On the other hand, they’d also expect to see non-amateur stations that were currently operating within the new international band limits move elsewhere as those frequencies became exclusively amateur allocations.

The ARRL had once suggested subdividing the 40- and 20-meter bands according to groups of geographically related nations, believing it to be an effective way to avoid interference. But the consensus now seemed to be that it was unnecessary, an optimistic view that Warner judged to be “a most healthy and wholesome sign,” even as he remained skeptical.

At least one thing was certain: equipment would have to change. The US was considering regulating transmitter power in certain bands and establishing power-supply requirements in order to abolish “the hated ‘raw a.c.’” from the air. And it was beginning to seem that modifying equipment to adhere to the new regulations would be less onerous than once thought, as new designs for higher-power transmitters, more-selective receivers, and more-accurate wavemeters were rapidly being developed.

Another big change was the use of frequency instead of wavelength. The Washington Convention specified allocations in frequencies, the world had adopted it, and it was finally time for amateurs in the US to do so as well.2 Besides wavelength being difficult to measure directly, its derivation from frequency, which was an easily measurable quantity, depended on the accurate measurement of the speed of light. That, in turn, got more accurate every year as science improved its ability to measure it. This meant that all precise notations of wavelength would change every time the speed of light specification did (in order to keep the same frequency). At short wavelengths, it was also much easier to talk in terms of whole cycles-per-second than tiny fractions of a meter.

But how many signals could fit into a given band? Here, the conventional theory went horribly, but temporarily, wrong. Most amateurs failed to anticipate the possibilities of ever advancing technology despite having witnessed it—or caused it—so many times.

They assumed that “Even the best adjusted station occupies a little slice out of the spectrum and this ‘slice’ is to be expressed as a percentage of its operating frequency, so that as we get into a higher frequency band we find that the width of the channel required for a single station is greater, and that a wider band will not necessarily accommodate more stations,” as Warner expressed it.

While proposing the use of frequency instead of wavelength, amateurs apparently missed the opportunity to stop thinking of signal width in terms of wavelength too. This was not due to signal bandwidth per se, but because of a practical consideration of the accuracy and stability of a transmitter’s signal, which properly could be expressed as a percentage of the operating frequency. This was partly Kruse’s “wabbulation” complaint.

In QST, Warner went so far as to present a diagram showing the relative widths of the 160- through 5-meter bands, taking into account transmitter accuracy as a percentage of operating frequency, showing that the practical width of 160 and 80 exceeded that of all the other bands combined. It also vividly illustrated the losses of space in moving from the pre-convention allocations to the new ones for 1929. And it showed how amateurs were no longer assured that their harmonics would fall automatically into a higher frequency amateur band.

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Warner’s band widths diagram, from September 1928 QST

Viewed in this manner, where effective signal width increases with frequency (e.g., a signal at 14 MHz would be twice the width of one at 7 MHz), the 20-meter band is seen to be the narrowest and most restrictive. The fewest number of signals could fit there even though it was wider (in kHz) than 40, 80, or 160. So, Warner used the center of the 20-meter band to define the center of the newly established family of harmonically related bands. Put another way, 14,200 kHz was the center frequency defining a set of harmonically related band segments in which harmonics were still guaranteed to fall within an amateur allocation, even under the new, narrower allocations. Prior to the changes (indicated by dotted line band widths), the harmonic centers coincided with the actual centers of all the bands (160m being the lone, slight exception), and they were all the same width – nice and neat. The new allocations abandoned this orderly plan to satisfy the intense demand for more frequencies coming from all services.

The 160-meter band ran from 1,715 to 2,000 kHz with a defined harmonic center at 1,775. It was allocated internationally to amateur, mobile, and point-to-point services, but in the US the Federal Radio Commission intended to license only amateur operations there. Amateurs used the band chiefly for phone operation and it was considered a good short-range telegraphy band too—a band for beginners and possibly for experiments in picture and television transmission.

The 80-meter band, from 3,500 to 4,000 kHz, had a harmonic center at 3,550 and was the only band to retain its pre-convention boundaries intact. It supported most of the amateur traffic handling. As with 160, it was allocated internationally for amateur, mobile and fixed services but the Commission, recognizing the importance of amateur traffic operations, intended to make it available in the US only to amateurs and specific military sharing as before. Mostly a telegraphy band, phone was again permitted from 3,500 to 3,550.

The 40-meter band, for telegraphy only, ran from 7,000 to 7,300 kHz, had its harmonic center at 7,100, and was considered the “million-dollar band,” the most heavily-used nighttime DX band, and was the segment most hotly contested at the international convention. It was “where we acquired the heartache and lost our shirt to Europe and Canada,” wrote Warner, adding bitterly that it was “viewed with envy and cupidity by a crass and vulgar commercial world.” Here, the League proposed to the worldwide community that the band should be used primarily for DX work, limiting intra-continent work to distances over 1,500 miles. It also proposed to divide the band according to geographic location, with the US staying primarily below 7,150 and the rest of the world in partitions within the upper half of the band (almost the opposite of what would occur years later). The geographic segmentation idea was never adopted.

The 20-meter band, which was 2-MHz wide before the convention, was now defined as 14,000 to 14,400 kHz, telegraphy only, with its harmonic center at 14,200. It was used primarily as a daytime DX band and for nighttime “super-DX.” A geographic segmentation was proposed similar to the scheme on 40 but, again, was not considered necessary by most and never came about.

Although the new 10-meter band occupied 28,000 to 30,000 kHz, it was considered half the effective size of the 80-meter band because of the percentage-based scheme for thinking about signal bandwidths and the resulting common practice for allocating commercial channels. Its harmonic center was at 28,400 kHz. Widely considered beyond the commercially useful upper frequency limit, the band was yet to be fully explored, though early users were reporting extraordinary propagation. It was internationally designated an amateur and experimental allocation.

Lastly, the old 5-meter band was recast as 56,000 to 60,000 kHz with a harmonic center at 56,800 and, like 10 meters, was also designated an amateur and experimental allocation, open for telegraphy or telephony.

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On-air operation and identity were due to change as well. The FRC announced that amateur call signs in the United States would begin using prefixes on 1 October 1928—W for the US and K for territories and possessions.3At the same time the DE intermediate would be used instead of the IARU’s nu.

As yet, there was no official news of what prefixes would be used by other countries, although there was an “international table of allocation of call signals” produced at the Washington convention from which countries must select official prefixes. A few countries were allocated entire blocks of single or multi-letter prefixes. For example, the US was assigned all prefixes beginning with W and France all beginning with F. Most countries were assigned ranges where two to three letter prefixes could be used, for example EAA-EHZ for Spain.

Procedurally, the biggest change was that CQ replaced QST as a general call, even for broadcasts.4 When used for a broadcast, one did not send K at the end—that was the only difference. QST became unassigned in the new list of Q signals, which had been expanded from the old list, and even had new meanings substituted for old ones. An officially agreed upon list of CW abbreviations was also issued, mostly intended for the fixed and mobile services, but widely adopted by amateurs as well. And a new audibility scale replaced the old R1 to R9 scale. It was a five-level scale added to QSA, as in “QSA 3,” which meant “fairly good” signal strength.

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The Federal Radio Commission announced in December that it would adhere to the international boundaries of the amateur bands below 6,000 kHz, assuring amateur use of 160 meters and the all-important 80-meter band where most traffic handling was done—“the only place in the spectrum where we really have room enough to turn around in,” as Warner put it.5

The US government had been a strong advocate for amateur radio throughout the post-war period including at the international convention. As everyone prepared for the changes in the coming year, the Commission in its annual report to Congress declared that “the amateur has sufficiently demonstrated his usefulness, both in furthering the progress of the science of radio and in furnishing service in times of emergency, to justify a liberal policy with regard to his operation.” And the Chief of the Radio Division at the Department of Commerce echoed the sentiment in his own report, writing that, “The amateur radio operators have received international recognition,” at the Washington convention, and, “his service as an experimenter and his value in promoting international good will recognized, and his continued activity assured by the allocation to him of certain specified wave lengths.”

Further acknowledging the less direct but equally important way amateur radio had influenced the radio industry by providing a training ground for engineers and industry leaders, the Radio Division chief asked the ARRL to “survey to determine to what extent amateurs and former amateur radio operators are occupied in the radio industry.” The survey found that “Of those engaged in executive positions in the radio industry, the list of amateurs includes 45 presidents, 16 vice presidents, 5 general managers, 69 managers, 37 owners, 324 engineers, 19 announcers, and 11 directors.” Though the Congress and general public may have found this surprising, for amateurs it was common knowledge.

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In a minor clarification, and a marked difference from how regulation changes had previously been handled, W. D. Terrell, Chief, Radio Division, Dept. of Commerce, informed Warner that the only change on 1 January 1929 would be the band limits.6 No station license recalls would occur, and holders of licenses issued before the turn of the year would receive copies of the new regulations.

A summary was printed in QST as requested by the Department of Commerce. Despite an intent to move to specifying bands by frequency instead of wavelength, they were still listed in wavelength order and it was evident that people still gave priority to wavelength when thinking about locations in the spectrum; for example, the 40 meter band was listed as 7,300 to 7,000 kHz, or 41.10 to 42.86 meters (opposite from how we’d do it today), and the full table ran from shortest to longest wavelength.7 Old habits die hard.

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  1. K. B. Warner, Editorials, QST, August 1928, 7.
  2. K. B. Warner, “We Ought to Talk Frequency,” QST, September 1928, 19.
  3. K. B. Warner, “Washington Developments,” QST, September 1928, 43.
  4. “1929 Abbreviations,” QST, October 1928, 41.
  5. K. B. Warner, Editorial, QST, February 1929, 7.
  6. “The New Regulations,” Correspondence, QST, February 1929, 54.
  7. K. B. Warner, “Revised USA Amateur Regulations,” QST, March 1929, 26.

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