70cm FPV transmitter

This is a scratch pad for a small 70cm FPV transmitter.

DTV is a bust. No one makes a single chip MPEG or NTSC to DVB or ATSC signal chip. Analog is easier, and the chips are kind of available.

Modulator: Can use the MC44BS373 or similar (NTSC RF Modulator). this takes a NTSC signal and modulates it up. Can modulate to arbitrary frequencies. 75 ohm output, so will need to convert.

Amplifiers: Need to go from -30dBm to about 30dBm, need lots of gain.

Final stage: PHA-202, but requires 11V. PHA-1H or -13H can put out 22dBm at 1dB, or 39@IP3, but input power at that is less than the output power, will need to investigate how that works.

First stage gain can use a CMA-545G1+ for 30dB of gain, also 5V.

Will need to use a SAW or really high q filter on the outputs, and shield.

Expected power usage is probably 5-10W, would reduce flight times by 20%, but range worth it.

Seems betaflight uses the MAX7456 for OSD display. Might be worth integrating? OR not. Dunno.

Here's info on a broadband amplifier that would take 1mW in, 1W out. Probably be cheaper than the minicircuits stuff , but more fiddly I'd guess https://yo5pbg.wordpress.com/2019/10/28/the-ultrawideband-1-1000mhz-nwdz-rf-pa-2-0-initial-tests-and-improvements/