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Marconi Wavemeter article
Marconi Wavemeter First Introduced in 1906 Wavemeters measure the length of waves; they determine the frequency of a transmission or help calibrate the dial of a receiver. They were one of the first pieces of test equipment developed at the beginning of radio. In 1906, G. Marconi first introduced the Marconi Wavemeter Number One in England. The first commercial wavemeter that Marconi made, it was used mainly for ship-to-ship and ship-to-shore communication. It typically covered the frequencies of 100-800 meters (this particular wavemeter, when introduced, was calibrated to measure from 200-1040 meters). You will notice in figure 1, the schematic of the Wavemeter Number One from an early Marconi catalogue, that the circuit is very simple, like a basic crystal set. I found the Marconi Wavemeter pictured in Illustrations 1 & 2 while living in Cambridge, England this past school year. It was a basket case. The glue was no longer holding and it was falling apart at all of the joints. The leather was dried and curled up. The leather had to be soaked to soften it and re-glued to the box on the left that holds the earphone. Because the wavemeter was in such poor shape, I was not sure how the finish should look. It did not look like other early Marconi apparatus I had seen. I tried to find one in someone's collection in the United Kingdom--no luck. The Science Museum in London had several later Marconi wavemeters, but not the Number One. I contacted the Marconi archives in England; they replied that they had an example of this wavemeter in their collection but would not let me see it because the archives are not open to the public. Bad news for those studying or restoring early wireless. Finally, I mailed some stain chips and a list of specific questions to the archives and got some answers. I found out what I suspected--the wood of the case was TEAK. Not mahogany, oak or walnut as one might expect in radios or wireless equipment, though it makes sense for equipment used on shipboard. Fortunately, about half of the original finish was still there so the rest of the finish could be blended in. The detector used in the wavemeter is a chunk of crystal wedged in-between two 2 inch long pieces of spring brass to the back left of the condenser. The small turned round wood box in the back of the earphone box is for spare crystals. The card in the lid is for calculating the wavelength. Surrounding the card wrapped in black tape is the coil. The Marconi Wavemeter Number One is a fine example of an early piece of test equipment. Copyright by John V. Terrey. Reprinted with permission of Antique Radio Classified where it was first published. For a free sample issue, write A.R.C., Box 2, Carlisle, MA 01741

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