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Look at the prior art. The key prior patent cited is BAESECKE, (2,134,850). This has a "wobbler" to change the transmitting frequency, which is fine, but that patent is vague as to how the receiving end stays in sync. Markey gets that syncing up transmitter and receiver is the real problem, and talks of it as a solved problem from television. (This is 1941, experimental TV exists.) Some mechanisms are discussed, borrowed from multiple player piano synchronization, which is where this technology came from. Voice cryptosystems of the pre-WWII period included the Western Electric A-3 scrambler [1] There's one on eBay! [2] That split audio into a number of frequency bands, which were shifted and reassembled. At the receiving end, the process was reversed. The shift pattern changed periodically, on the order of tens of seconds. That was slow enough that keeping the thing in sync was possible with clockwork of the period.
Note that this is working on the audio, not the RF; it's a scrambler, not a frequency hopper. This is what AT&T used for transatlantic commercial voice. Worked OK, mediocre security. Only 6 different frequency shift patterns were in use at a time. The Germans cracked it. This is not the better known SIGSALY. That's a similar concept, but with a lot more audio channels, much more frequent changes, a one-time key for the changes, and more hardware than some mainframe computers.
The A-3 was a desk-side wooden box. Neither system does frequency-hopping of the RF signal. Hedy Lamarr's first husband was an arms manufacturer, and she apparently paid attention when visiting the factories. Hence the radio-controlled torpedo, which is close to Tesla's radio-controlled boat. MARKEY (2,292,387) describes a cross between a radio-controlled boat and a set of synchronized player pianos. There's some handwaving around the sync problem. The trouble with syncing a frequency hopper is that you have trouble even finding the signal to get started. But if you're launching a torpedo or a bomb from a larger craft, both ends of the connection can be started in sync and will probably stay in sync long enough for the bombing run. Doing this with a player piano roll reader, vacuum pump and all, is probably not the right approach. Trying to get things to sync up reliably has a long history. Edison's first useful invention was a way to get stock tickers to sync. There's a long history of clunky mechanisms, early ones involving flywheels or big tuning forks, and later electronic ones with too many screwdriver adjustments.
Not until the invention of phase locked loops did it really Just Work. (I'm into restoring early Teletype machines, and I'm way too aware of the early days of sync problems.) Markey was just too early. Reasonable idea, but not practical at the time due to lack of supporting technology. [1] https://chris-intel-corner.blogspot.com/2012/02/intercepted-... [2] https://www.ebay.com/itm/205373065319 |