![]() But you’re very limited to how much data you can send. Low frequency bands like this are useful cos they travel a long way. Satellite comms are usually up in the GHz. A quick search tells me some fish finders use 77KHz audio as ultrasound sonar, which gives a good idea of how low a frequency it is. “, and you REALLY do NOT want to get one of those letters, especially if you currently hold any kind of radio licence (ham, general operator, boat, aviation, commercial…)ħ7KHz is barely radio, I’d be amazed if anyone sent speech over it. §15.107 and 109 give limits on how loud you can be, but only at frequencies above 150 kHz.īut §15.5 also says “(c) The operator of a radio frequency device shall be required to cease operating the device upon notification by a Commission representative that the device is causing harmful interference. Which implies that if you keep it quiet, it won’t be an issue. However, interestingly, Part §15.205 “Restricted bands of operation.” makes no mention at all about operation at 60 kHz.Īnd §15.5 “General conditions of operation.” says: “(b) Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused” If you’re subject to the US FCC, you’re welcome (nay, *required*) to study 47CFR part 15, which details in glorious detail exactly what you may do with specific frequencies. Posted in Radio Hacks, Raspberry Pi Tagged 3d printing, atomic, dcf77, JJY, MSF, radio, raspberry pi, txtempus, watch, wwvb Post navigation We’ve seen WWVB emulators before, like this ATtiny45 build, but we love that this solution is an easy command line tool which supports many geographical locations. Be sure to check the rules in your area before giving this a try. This might be just as well, given that we recently wrote about the possibility of WWVB being switched off. also kindly took the time to implement the protocols for WWVB (US), MSF (UK) and JJY (Japan). The whole thing sits in a slick 3D printed case, which provides a stand for the watch to rest on at night this means that every morning it’s synchronised and ready to go. The Raspberry Pi syncs with NTP Stratum 1 servers, which gives the system time an accuracy of about ±50ms. A second GPIO performs the required attenuation, and a few loops of wire are sufficient for an antenna which only needs to work over a few inches. ![]() ![]() The signal is AM, and transmits one bit/s, repeating every minute. Consequently, he decided to make his own tiny transmitter, which emulates the DCF77 signal and allows the watch to synchronise.Ī Raspberry Pi Zero W is the heart of the transmitter, and manages to coax it into generating 77500.003Hz on a GPIO pin – close enough to the 77.5kHz carrier that DCF77 uses. lives in a place where there is no reception of the DCF77 signal that his European wristwatch expects to receive. Or, at least, you can if there’s any signal. You can win any argument about the time when you have a radio controlled watch.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |