In our Elektor Labs designer Ton Giesberts has been working on a circuit capable of helping to find your lost RC model plane after it made an unfortunate landing somewhere into a corn field or undergrowth. The prototype is built up and running smoothly. But I wouldn't be writing this piece if it wasn't for something strange happening while testing the circuit in our labs. Apart from the receiver functioning correctly in conjunction with the transmitter module, the receiver also picks up a repetitive signal that sounds like three short beeps, with an interval of about a minute or so. When hooked up to a scope, we see the three beeps look like they are Manchester-coded communication signals. Although the receiver is tuned to the 433 MHz ISM band, frankly we are clueless about the origins of these beeps. We surmised it could be the fire alarm sensor installation or the burglar alarm system.
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