Path: utzoo!utgpu!CUVMA!SWL-L Date: Sat, 24 Feb 90 14:39:40 EST Reply-To: 99700000 Sender: Short Wave Listener's List From: 99700000 Subject: Re: Determining Listening Audience Size X-To: swl-l@cuvmb.cc.columbia.edu To: UofToronto LAN redistribution Message-ID: <90Feb24.144359est.57352@ugw.utcs.utoronto.ca> Newsgroups: bitnet.swl-l Distribution: ut Approved: devnull@gpu.utcs.toronto.edu I believe it's done by calculation, at least for local AM/FM stations. Given the transmitter power and the antenna characteristics you can calculate zones of signal strength about the station. You can correct the calculations by making field strength measurements in the field (no pun intended). You can draw these on a map - for AM you have to have separate day and night calculations if the station operates at night. I remember seeing in a small-town newspaper, when the local AM station was going for a power increase, a map of "before" and "after" coverage within which the signal is strong enough to be easy to listen to. >From that point you can count the houses on the map and estimate the number of people per household, etc. That takes care of the simple case out in the boondocks where there is only one local station. For urban areas I guess they have to estimate the percent of population listening to each available stations by some other process.