[aprssig] Nuclear Power Plant Icon?

[Robert Bruninga]

I guess the question becomes, how close does a "cheap"
detector have to be to a "dirty bomb" to detect it?
If it is feet, then this is a dead end.

If it is 100 yards, then some detectors on some
highway overpasses might be interesting..? bob

>>> scott at opentrac.org 07/21/06 10:39 AM >>>
> Is there a way to make a smoke detector into a cheap radiation
> sensor?

Don't think so.  Even if you could, they'd only be useful for detecting
alpha radiation emitted by something actually IN the detector.

I seem to remember hearing that CdS photocells would detect gamma radiation.
I wouldn't expect them to be terribly sensitive, though.

What do you consider cheap?  The expensive part of a Geiger counter is the
tube itself.  Last time I checked, I could get new alpha/beta/gamma
detecting tubes for around $40 each.  Electronic Goldmine sells a small
gamma tube for $35, but it's small and insensitive - maybe 1/10 as sensitive
as the new ones I was looking at.

Velleman sells a kit based around one of those small, insensitive tubes for
around $150, which sounds awfully high to me.  I'm sure I could build an
APRS-suitable kit for under $100.  You need several high-voltage capacitors,
some diodes, and a transformer, but they're not all that expensive.  My
prototypes were built with LCD displays from one of the surplus outfits, but
for APRS you wouldn't even need that.

The main drawback of my circuit as it stands now is that it's got a very
inefficient shunt regulator on the high voltage side.  A better design would
improve battery life considerably.  If anyone wants to provide some input on
that, maybe I'll take up the project again.  Some input on high voltage
safety would be appreciated, too - I want to be sure that some component
I've selected won't eventually degrade, start arcing, and catch fire.

Scott
N1VG




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