FM Transmitter

[jmoorsie]

I'm trying to construct a simple FM Transmitter using the MAX2606 IC. I have the manufacturers data sheet and everything, but i have no idea what to do with the signal inputs( L and R rca jacks). I have two potentiometers of 1K and 10K, along with various caps and resistors. Also there is the issue with the inductor, the data sheet claims i should place it directly between pins 1 and 2, but they're nanometers apart.... I know these are rookie problems, but i am very enthusiastic about electronics, and lets face it... you gotta start somewhere!

 

[mneary]

The MAX2606 isn't an FM transmitter chip.

About as simple as you can get for an FM transmitter are those based on the BH1417F chip, which is an FM stereo chip with 8 available frequencies. Futurlec prices them at us$2.90.

Yes the pins are close together, but these parts are designed to be used with surface mount parts. Inductors, resistors, and capacitors are as often 1mm long. (Actually in industry, the 0.5mm parts are becoming popular.)

 

[jmoorsie]

Though the max2606 may not be ideal for the transmitter, it came in a box labeled 322ITTMAX3606-FM TRANSMITTER. But never mind that, lets get to that BH1417F, have you ever used it?

 

[audioguru]

The MAX2606 FM transmitter is a child's toy. Maxim publish the FM transmitter applications note separate from the datasheet.
It doesn't have a quartz crystal so its frequency wanders.
The circuit shown is mono, not stereo.
It doesn't have pre-emphasis (treble boost) like FM radio stations have and like FM radios expect, so it sounds like an AM radio or like your stereo with its treble tone control turned all the way down.

The BH1417 FM stereo transmitter IC is used by many manufacturers of an MP3 to FM transmitter for cars. It uses a quartz crystal in a frequency synthesizer with a has a phase-locked-loop. It has pre-emphasis so it sounds great.
Silicon Chip magazine had a project for it. A kit is available.

The BH1415 and BH1416 ICs are used with a microcontroller and the circuits have a frequency display.

 

[mneary]

I've never built anything from scratch using the BH1417F, but I own several "FM adapter" modules that incorporate it. They seem to work well, but you must remember this is FM stereo with one chip so it isn't commercial quality.

 

[audioguru]

you must remember this is FM stereo with one chip so it isn't commercial quality.

Rohm should be applauded for cancelling production of their horrible BA1404 FM transmitter IC (it is still used in many kits) and producing this new line of FM transmitter ICs. They work very well.