Re: Digital FM transmitter

Connect Microchips PIC10F200 to the control pin of a Fox RFV250.Just two small parts (but might not constitute "all digital").

Thomas

And then? It can not be possible to do all thats needed in this part?

It has at least 16 ADC's that can sample at good freq to do good FM?

FM as in 106.7Mhz?

Sorry, 88-108Mhz FM :-)

I thought it would give you better THD, SNR, stereo seperation

Thanks.

My point was that the original poster did not specify what kind of FM transmitter was being mimicked. Frequency modulation, in it's simplest form, only requires an interface to the control voltage of a VCXO at the appropriate frequency.

P.S. FM doesn't only exist at 88-108 MHz.

Thomas

is

Analog Devices has an app. note with a basic DSP dev. kit and one of their DDS chips. They use a mirror/harmonic of the DDS signal to get to the 3m band. May need some filtering to comply with FCC rules.

Wim

As the frequency setpoint is stepped at the audio sampling rate (48 kHz or 44.1 kHz in the AN-543), there will be extra sidebands at the sample rate and its multiples. This is because there is no audio signal reconstruction filter before the modulation (and in this application there's no way to include it). The only way out from this problem is to change the frequency setpoint at each RF sampling cycle which would need a

The signal is crisp and clean on a FM receiver on channel, but there is plenty of crud outside the allowed bandwidth.

The trick used by the AD app note is to use the aliased frequency (125 MHz clock - set frequency) as the payload output.

The app not device is OK for a directly connected FM receiver, but not suited to be connected to an antenna.