Re: How much power can I receive from a FM station

On Nov 10, 1:10 pm, Allen <ocean...@xxxxxxxxx> wrote:
I am designing a FM radio receiver. Can anyone tell me show much power
can I receive from a FM station that is in a acceptable range? I need
that value to decide the gain of all the stages. Thanks.

Allen

Usually FM receivers are designed with excess gain, since there is no
need for amplitude linearity. You didn't say what sort of FM station
you want to receive. FM signals vary greatly in the bandwidth they
occupy: communications channels (police, fire, pagers, etc) are
typically only a few kHz wide, and FM broadcast is typically about
150kHz wide. That makes a difference: since you'll pick up about the
same amount of noise per unit bandwidth (atmospheric noise; galactic
noise; ...) for signals at approximately the same carrier frequency,
the total noise in the channel varies with bandwidth. So for wider
bandwidth, it takes more signal to rise above the noise and be
useable. A reasonable goal for FM broadcast at 100MHz would be to be
able to receive signals greater than -165dBm/Hz bandwidth, or about
-114dBm. That's about half a microvolt at 75 ohms, I believe.

You may wish to think about a bunch of other things before going very
far with your project: how will you avoid distortion from big signals
when you are trying to listen to small ones? How will you filter out
frequencies (channels) other than the one you want to listen to? How
will you maintain phase linearity so you achieve low distortion?

If you don't get discouraged along the way, and you keep your eyes and
mind open, you'll discover that there's a lot more to designing a good
receiver than initially meets the eye. And I want to make it clear
that I do NOT want to discourage you, because it's by doing things
like that that you will learn, possibly learn a whole lot.

Cheers,
Tom

.

Relevant Pages

  • Re: Difference between IDE and SCSI ??
    ... The bandwidth in bits is due to ... minimizing the inherent noise, and maximizing the signal to noise ratio ... radiated noise yeilding signals that can actually be plucked from below ... yielding greater transmission distance ...
    (Fedora)
  • Re: looking for high value resistors
    ... Coz otherwise I'd turn the gain knob on my Keithley 427. ... >>the higher gain since the spectral noise density is lower and thus the ... > two-component transresistance amp) automatically lowers your bandwidth, ... > the cost of more noise, still requiring you to use long integration. ...
    (sci.electronics.design)
  • Re: Recording XM signals...an issue
    ... I use to work in the spread spectrum world ... >>bandwidth angst to the junk yard. ... >>other signals cluttering any given bandwidth allocation....with enough ... >>noise in the traditional S/N become of historical interest. ...
    (rec.audio.tech)
  • Re: Recording XM signals...an issue
    ... The noise immunity in SS is even greater. ... I use to work in the spread spectrum world ... >>bandwidth angst to the junk yard. ... >>other signals cluttering any given bandwidth allocation....with enough ...
    (rec.audio.tech)
  • Re: searching better alternative for LM386
    ... The signals are synthesized sine waves and tone bursts coming from a ... Important for this application is that the gain of the amplifier is low ... to keep a decent signal to noise ratio. ... So, basically I'm looking for a better audio amp, similar to the LM386 ...
    (sci.electronics.design)