[aprssig] APRS radiation sensor

[Guido Trentalancia]

We actually have an addendum for the new weather measurements:

http://www.aprs.org/aprs12/weather-new.txt

However, according to a series of documents named "ANSI N42" and used in
homeland security, the recommended unit for the radiation might not be
sievert but roentgen (see for example section 4.2 of N42.33 for portable
devices, published in 2006).

The ANSI N42 standard also recommends an operating range from 5 uR/h
(0.01 uSv/h) to at least 10 mR/h (0.1 mSv/h) (5.4.1) or to at least 2
mR/h according to document "ANSI N42.32" for personal devices at
(5.6.1). There are also many other minimum requirements such as for
batteries that last a minimum of 16 hours (5.11.1) or a minimum of 8
hours according to document "ANSI N42.43" for mobile and transportable
devices (8.4.1), accuracy within +/- 30% over entire range (6.2.1),
response time within 5 seconds (6.4.1), temperature range from -20 to
+50 celsius (7.1.1) or from -30 to +55 celsius according to document
"ANSI N42.43" for mobile and transportable devices (7.1.1), humidity
(7.3.1), maximum false alarm rate of one alarm per 10 hour (document
"ANSI N42.32" for personal devices at 6.2.2).

Most of the N42 standard is available from here:

http://standards.ieee.org/about/get/

Comments are welcome.

We could inherit some requirements or otherwise reference the standard
directly for example...

Guido IZ6RDB