[time-nuts] Toy radiolocation and LORAN envelope

[Mark Sims]

I fly large model rockets and radio tracking beacons are very common in this application.   Most are based upon wildlife/bird tracking products.  Walston Retrevial Systems makes some very good systems.   They run on button cells and can ping for a few days to weeks.  Most operate around 220 Mhz.  A handheld yagi attached to a receiver with a good gain control is used to localize the signal.
http://www.walstonretrieval.com/main.htm
The schematic of one simple pinger transmitter is attached.   It requires a bit of futzing with component values to get the circuit to ping.  Transistor/crystal selection is important.  I set mine up to run on a 3V cell instead of 1.5V   I get about a 1 mile range in open conditions.  Fancier versions add a buffered output stage. 		 	   		  
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