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Radios

There are a number of radio modules in use with descriptions :

Module	Price	Temp Stability	Complexity	Frequency	Modulation	Further Information
Radiometrix NTX2	Low	Poor	Simple	434.075 or 434.650	SSB RTTY	Data Linking an Arduino to a Radiometrix NTX2 Transmitter
Radiometrix LMT2	High	Excellent	Simple	433.900 → 434.650	SSB RTTY	Data
Radiometrix TX3H	?	Poor	?	869.50Mhz	SSB RTTY	Data
Radiometrix HX1	Medium	Good	Moderate	APRS 144.800/143.900/144.390	FM APRS	Data
HopeRF RFM22B	Low	Poor	Moderate	413.000 → 453.000	SSB RTTY + Others	RFM22B Insulation is very important with this module, the crystal is only rated to -20'C. The module has exhibited instability and failure when exposed to low temperatures. It is recommended to reboot the module every 20 telemetry transmissions.

Notes :
“Poor” stability means unless well insulated the frequency will drift noticeably.
“Simple” Complexity means suitable for beginners.