forget-me-not transmitter

7-64 — elektor july/august 1981 67 forget-me-not. _ transmitter Are you fed up with losing things, of putting valuables down and forgetting all about them? Now you can relax, thanks to the very useful gadget to be described here. The small receiver in the next article is carried around in a pocket. The item, or items, (such as baggage, handbags, wallets etc.) con- tain an even smaller transmitter. An alarm is set of 1,5 ... 9 V as soon as the distance between you and your pos- sessions exceeds a certain range. This informs you that you have lost, dropped or forgotten the article in question, or that is has just been stolen from you. The transmitter is merely a low power oscillator coupled to a small loop antenna. By not allowing the radiation resistance to be of o low a value, the tuated in the low operating frequency can not bets - frequency end of the radio spectrum. As a reason able compromise the frequency was chosen to be 42 MHz, which is between shortwave and VHF televisio...