SRB MX145 Transmitter

Note: The MX145 replaces both the 5-volt and 8-volt versions of the MX146.

The MX145 is an embeddable VHF transmitter module from our friends at SRB Electronics. It's programmable for any frequency from 144 to 148 MHz in 2.5 kHz steps, or you can use it on one of 16 pre-programmed frequencies.

Power output is 350 mW minimum, and typically closer to 500 mW. It draws under 1 mA in standby, has a fast wake-up time (< 25 ms) and is suitable for voice or data with bitrates up to 10 kbps or more.

The MX145 makes a perfect low-power APRS tracker transmitter, and its light weight is perfect for high altitude balloon payloads, model rockets, and R/C craft.

Don't confuse this transmitter with the cheap crystal-controlled 'model rocket' transmitters you might find elsewhere for a similar price. It not only exceeds the standards required by the FCC in Part 97, it exceeds the engineering standards of most mass-market amateur equipment currently on the market. It's made in the USA and designed by German engineers who are, quite frankly, just a little bit fanatical about quality.

An Eagle PCB library is available for those integrating the MX145 with their own board designs.

Technical Speifications:

Frequency range:144MHz to 148MHz
Channel spacing:2.5kHz
Modulation:digital injection modulation
Modulation Bandwidth:>20kHz
Modulation Sensitivity:23kHz/V (typ)
Input Impedance:~600Ω
Spurious suppression:> 80dB (channel spacing > 10kHz, typ)
Harmonic suppression:45dB
Frequency stability:+/5ppm (typ)
Turn On delay (after PTT):25msec (typ)
Output power:> 350mW (minimum) into 50Ω
Programming:SPI® and I2C® interface or 16 preprogrammed frequencies, pin selectable. 3.3V CMOS level
Supply voltage:+5VDC (4.7V to 6V)

User's Manual
3D Model (STEP format)

Support is available at the SRB Electronics Yahoo group.