If that equation were just attenuation over distance, there would be no frequency factor, or at least the attenuation would not be directly proportional to frequency. So the equation is somehow taking into account antenna characteristics (i.e., it is not attenuation, but path loss, quite different). I don't know what type of antennas are assumed, but one thing is for certain, AM XMIT/RCV antennas are very different than 2.4 GHz antennas. So you have to back out the 2.4 GHz antenna factors/gains/apertures and substitute those for the AM link (high field intensity source, electrically short whip or loop receive antenna). The other thing to note is that I would expect a 2.4 GHz link to operate over a range of one hundred feet or so, while an AM broadcast link covers many miles. The equation you cite cannot take into account the various boundary conditions encountered over an AM link that affect AM signal strength in a small local area (like passing under a bridge).
From: "George Stults" <[email protected]> List-Post: [email protected] Date: Thu, 2 Dec 2004 10:48:25 -0800 To: <[email protected]> Subject: path attenuation in AM band Hi Folks, I have an equation for the attenuation of a radiated signal as a function of (distance, frequency, and environment.) ATTN = 37 + 20 Log (Freq) + 20 Log (Dist), Freq is in MHz, Distance in Miles, Environment is free-space/line-of-sight (N=2). My information is that this equation works well for 2.4GHz frequency range. Could anyone tell me whether this equation would still make valid predictions for attenuation in the AM band. (535 1650)Khz, and lower? Or could anyone suggest an equation that would predict path loss as a function of distance, frequency, and environment for lower frequencies? Thanks in advance. George Stults ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
