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*Subject*: Path loss and signal calc...*From*: Anthony Bombardiere <ab2cj@xxxxxxx>*Date*: Tue, 03 Feb 1998 17:33:37 -0500

Hi all, AF9Y calculated the path loss for the Mars probe at -179dbm. If the average receiver has a minimum disernable signal of -140dbm. How can one hear a signal thats -39db below the receivers noise floor? I would assume that antenna gain and any pre-amplification is taken into account, and the fact that Mike,(AF9Y) used his DSP program to graphically display this signal that could not be heard by the human ear , but how can one receive a signal that is far below that of the receivers noise floor? Is the calculation for this problem as simple as taking the preamp gain and antenna gain and adding them to the path loss of the signal? If so, assuming a total gain in the system of 50db then.... -179dbm + 25db(pre-amp) + 25db(antenna gain) = -129dbm ????? Also, if the sensititvity of a receiver is said to be .2 micro volts at (10db s+n/n), that would mean that the receiver would produce a signal of 10db above the noise for an input of .2 uv. How can one relate this mesurment with signal strengths that are expressed in dbm or decibles as they relate to microvolts? That is, how does a signal that is said to be -140dbm relate to the measument of .2uv at (10db s+n/n) Its obvious that I'm not sure of my math skills, but I had to ask... Thanks , AB2CJ

**Follow-Ups**:**Re: Path loss and signal calc...***From:*Raul Gomez Fernandez

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