Dr. A. Hoyt Taylor: Gadgets
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Dr. A. Hoyt Taylor:
"Gadgets" 

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Lots of gadgets tested at Belmar, Hoxie photographic recorder, Vreeland - audio frequency filter and G.E receiver.

During this period we had a number of interesting visiting engineers or scientists who had gadgets that the Navy Department though might help reception. Hoxie brought his photographic recorder, which made a record of the incoming signals on moving film which was developed as it ran along. This was really an interesting instrument, 'permitting good discrimination between signals and static, and permitting higher speed of reception than you could possibly get with the human ear. But it had a bothersome defect, inasmuch as it took some minutes to develop the film. It also took a separate set of operators to read the film, because such operators, or film readers, had to be specially trained for the job. Ordinarily, in such work, if the operator loses a word he “breaks” the transmitting station. This is done by opening up one of our own transmitters at the touch of the key, and sending a prearranged signal which causes the distant transmitting operator to stop his transmission and listen. We then tell him to go back to the last intelligible word we have correct, and continue on from there; thus errors in reception can be corrected at once and filled in, whereas with the Hoxie recorder this was impossible, because we had to stop and read the film. By that time the transmitting station had gone many words ahead. Nevertheless, the Navy bought some of these recorders and we learned a lot from them; they had their good points.

Another device to improve reception was brought down by Dr. F. K. Vreeland. This consisted of a very sharply tuned audio frequency filter, or the equivalent of it at least: Since continuous wave reception involves listening to pure tone, and since the ear hays considerable power of discrim-ination against the rough noise of static, a filter such as this would favor the tone against the static and would seem at first glance to be very valuable. When Vreeland's device was first connected to a receiver, to the casual listener there seemed to be a marked improvement, but when I brought two of our best operators to copy fifteen minutes, first without the device, and then with it, we found that both made better copy without the device. The difficulty was due to the fact that the static caused the filter to “ring” so that the static had a musical note of the same approximate pitch as the signal. The ear was not able to distinguish well enough between these two things. I think we all found out, a few years later, that this filter device had to be applied with considerable caution. The filter should not be too sharp, or ring too easily, else it will do more harm than good.
Page updated December 30, 2003  page created September 02, 2000

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