tomv@s1.msi.umn.edu (Tom Varghese) (03/14/91)
I am looking for an simple, cheap FM transmitter/receiver circuits to use as a medium for digital data transmision over a short range (~100 yards).... I was wondering if there are any single chip solutions for this.
kellym@ether.UUCP (Kelly M McArthur) (03/20/91)
In article ... tomv@s1.msi.umn.edu (Tom Varghese) writes: > >I am looking for an simple, cheap FM transmitter/receiver circuits to use >as a medium for digital data transmision over a short range (~100 yards).... >I was wondering if there are any single chip solutions for this. Motorola's MC2833 might be useful to you. It is a single-chip FM transmitter with an audio input you could use for FSK, and a built-in microphone preamp you can loop back into the audio input. In addition, if you call the Motorola folks in Phoenix, they'll cheerfully send you a little evaluation PCB you build up a test circuit on (or at least they did for me). The part is found in the "Linear and Interface Integrated Circuits" book. The data book lists values of caps and coils to operate this device at 49.7 MHz, 76 MHz and 144.6 MHz (note that values for operation at ~100 MHz are conspicuously absent :~) ). Power output is listed as +5 or +10 db. (BTW, how do you relate this to something like milliwatts, for those of us who don't speak RF-ese?). Have Fun, -- ******************************************************************** * Kelly McArthur ..tektronix!sequent!ether!kellym * * HALF Associates (Heavily Armed Lunatic Fringe) * ********************************************************************
tomb@hplsla.HP.COM (Tom Bruhns) (03/22/91)
kellym@ether.UUCP (Kelly M McArthur) writes: >at ~100 MHz are conspicuously absent :~) ). Power output is listed as >+5 or +10 db. (BTW, how do you relate this to something like milliwatts, >for those of us who don't speak RF-ese?). Normally they would be listed as such-and-such dBm, which means dB relative to 1.0 mW. So +10dBm is 10 milliwatts. Sometimes they shorten it, get lazy, and just say, "dB." If it's RF and they don't list any other reference, it's _probably_ dBm. -90dBm 1 picowatt You can cover quite a range in -60dBm 1 nanowatt dB from -99 to +99 ! -50dBm 10 nanowatts (though radio receivers are -40dBm 100 nanowatts commonly sensitive to well -30dBm 1 microwatt below -90dBm -- but can't handle -20dBm 10 microwatts +90dBm ;-) -10dBm 100 microwatts 0dBm 1 milliwatt +30dBm 1 watt +60dBm 1 kilowatt +90dBm 1 megawatt Other segments of the industry use other references; dbV is db referenced to one volt, and some folk make extensive use of dBfs (dB relative to some full scale reading) or dBc (dB relative to a carrier signal).