[time-nuts] Small quantity custom crystals

jimlux jimlux at earthlink.net
Fri Oct 1 22:54:56 UTC 2010


Mark Sims wrote:
> This type of circuit is NOT a free running oscillator.  It is a type
> of blocking oscillator that generates a short,  high powered ping
> every second or two.  It is designed to be able to extract every bit
> of power out of the battery.  It can run for over a month off of a
> couple of button cells,  yet generate a signal detectable over a mile
> away while it is laying flat on the ground.  The allowable frequency
> bands are at 216, 217, and 219 Mhz.  Each unit must be on its own
> freq,  hence the need for one-off custom crystals.
> 
> Yes, it is a weird circuit and depends upon all sorts of unspecified
> parameters.  The components have to be hand selected and matched.
> This is the price one has to pay for this sort of operation.
> 

This is comparable, then, to the wildlife transmitters for Argos (which 
are at 400MHz-ish).. Does this application need good medium term 
stability (i.e. are you making a series of Doppler measurements?)


> --------------------------------------- -Build a free running
> Colpitts oscillator and get it tuned to the frequency you want.
> Then, insert the crystal in series with theemitter. 
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