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===== TX3H =====

The TX3H is a Radiometrix 869.5MHz module which provides 450mW of output (up to 500mW is allowed for airborne use in this frequency band). The TX3H is a 5V Wide-band FM module which like the NTX2 has analogue input on the data pin. The input voltage to frequency characteristics of the TX3H are shown in the graph below - and is approximately 11kHz/V about the 2.5V input centre point. The graph shows frequency offset (kHz) against data input voltage over the range 0 - 5V.

{{guides:tx3ha.jpg|}}

TX3H temperature stability is worse than the NTX2 (as might be expected of this higher frequency module) - also noticeable heat is generated by the module due to the higher power and lower efficiencies at higher frequencies.  

The regulatory requirements of airborne operation in this band are a channel bandwidth of less than 25kHz, less than 500mW ERP and less than 10% duty cycle. The latter requirement reduces the heat dissipation issues.