Tuesday, 9 December 2014

The Importance of 1929 - Part 2

W6BAM - 1929 Compliant. Courtesy : N7RK
The men and women of the 1927 Washington Conference had produced a huge volume of new rules for radio broadcasting, signed by delegates from 72 countries. Each country was left to implement the new rules as they desired. Most of the rules were to take effect as of January 1st 1929. There was no turning back now.

It wasn't long before the ARRL shifted its focus to the new days ahead and seemingly, every issue of QST leading up to the 1929 implementation date, addressed the topic. It is of interest to see how the ARRL interpreted the new rules and developed a strategy to meet the requirements. Many of the rules were broad enough to allow for varied interpretations, all of which could be compliant. In hindsight it seems they made a very good choice on the best way to tackle the present mess on the ham bands...to inform every ham possible of his or her responsibilities for meeting the coming challenge and to show them how.

As far as amateur 'experimental' radio was concerned, the delegates addressed several critical points...in fact, the very recognition of amateur radio itself was a significant step forward for hams worldwide:

"Article 1, {16} the term "private experimental station" means -- (2) a station used by an "amateur," that is, by a duly authorised person interested in radio technique solely with a personal aim and without pecuniary interest."

Although not as big an issue in North America, where governments had long-supported ham radio, for many countries it would mean operational status would now be recognized. The ARRL's campaign to convince hams that their stations must be 'DX-ready' was now given some teeth. Thus began the campaign to convince hams that their 1928 junk must go:

"...for the great average of American amateur stations...it is not a reassuring spectacle in view of next year's requirements. We seriously doubt if as many as one-half of one percent of the active stations to-day are good enough to offer their operators any reasonable chance of success in international work next year. The rest, we think, will have to be rebuilt....floppy waves, bum notes, crawling frequencies, too-big condensers, sloppy practices, haywire assembly, and lack of precision measurements...These must go.. " [QST Editorial,  May, 1928]

It sounds alarmingly descriptive of our annual BK Party...but proclaiming that 99.5% of U.S. amateurs would need to rebuild was surely a bold statement and one, as time went on, was gradually toned-down in QST editorials. 

Addressing the 'haywire assembly' issue, articles soon appeared showing better construction practices for earlier familiar designs, the self-excited favorites.

Courtesy: WØVLZ
One landmark article by Ross Hull in August, 1928, set the tone for what was coming. In his "Overhauling the Transmitter for 1929" Hull proved that the favored Hartley, or any other self-excited oscillator, could be built to 1929 standards with a series of elaborate tests and measurements. The article highlights construction of what has become a favorite project to this day, the "Hull Hartley Oscillator". The genius of  Hull's design is shown here in an exacting reproduction by Niel, WØVLZ who posts an equally fascinating description of the project here.

Read with caution as you will likely be tempted to begin the parts-search for you own version soon after. It was Niel's superb series of videos that inspired my interest in 1929 construction.

Hull's 1929 MOPA. Courtesy: http://www.arrl.org/
The apparently never-resting Hull continued the following month with two more construction articles, the first one being "The Oscillator-Amplifier Transmitter / A Practical Study of Its Suitability for 1929 Operation". Once again, in exacting detail, he shows the masses how to construct a suitable MOPA design, calling it "a real 1929 transmitter".

Hull's High-Powered 1929 Self-Excited Transmitter. Courtesy: http://www.arrl.org/

The second article in the issue, "Adapting Medium and High-Powered Self-Excited Transmitters for 1929 Service / Some Design, Constructional and Tuning Considerations Involved", was described by Hull... 

"For a week or more, the Laboratory was filled with odors of burning bakelite, hard rubber and wood, and at times whiffs of smoke drifted lazily across the tables -- but in the end our pulse had returned to normal, for we had found that even 250-watt self-excited transmitters can be made to behave in a 1929 manner with just the same treatment we had given the low-powered set".

As noted earlier, it was of interest to see how the men at ARRL interpreted the new rules to such an extent as to call for a complete overhaul of transmitter construction. The Washington delegation had only provided a broad hint as to what must be done regarding stability and spectral purity, while still craftily ensuring that transmitters would always be required to remain "state of the art":

"Article 5, {18} (3) ..the frequency of the waves emitted must be as constant and as free from harmonics as the state of technical development permits"

The ARRL took this opportunity to push the "state of technical development" as it concerned amateur radio. Hull defined the requirements for a 1929 signal as:

"...must be entirely within the limits of the band....its frequency 'flutter' due to irregularities of plate supply must not exceed about 1/30 of 1% (approximately 250 cycles at 40 meters). In addition, the frequency of the signal must be relatively constant. The signal must not 'shimmy' as the antenna vibrates, it should not 'chirp' as it is keyed, nor can it "creep" appreciably as...the tube heats. In short, the frequency of the first dot transmitted should be within 1/10 of 1% (about 750 cycles at 40 meters) of the hundredth dot, even if the plate has reddened...or the voltage drifted. At the end of a few hours of operation the frequency should not have strayed much further." [QST August, 1928]

By today's standards, not a tall order, but in 1928, there was much to be done.

With the deadline fast-approaching, the vigorous campaign to drag hams out of the cesspool of clicks, harmonics, wide signals, raw AC and into the promised land had begun....lead mainly by the hands of George Grammer, Ross Hull, James Lamb, Robert Kruse and Beverly Dudley, nirvana was just over the horizon and surely could be reached .....but only if they rebuilt their 1928 'heaps'.  (cont'd)

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