The Prius seems to have a number of antennas: 1)AM 2)FM 3)XM 4)GPS for Nav 5)GPS for Safety Connect 6)Cellular for Safety Connect. Are all these things integrated into the horsewhip on the roof?
pure conjecture: AM is usually within the radio FM is definately the whip XM/GPS can be in the base of the whip GPS for safety connect, can be the same as the nav gps. no idea of the cellular radio for safety connect, as i dont have it.
The Toyota site has the one in the back window as the AM/FM. I ask a guy at Toyota one day and he said that the roof and the one in the back window are AM/FM, don't know why it needs two though?? Toyota Prius Hybrid - 2012 Models: Prius Two, Prius Three, Prius Four, Prius Five
well.. FM with two antennas gets better reception.. called Dual Diversity Antenna.. in order to get better signal. from my experience, it needs more. as it is, the radio or a controller, can select from two antennas to get the best signal. as far as AM goes, the antenna length is SOOO long that is usually found as a spool of wire around a cardboard tube buried in the radio innerds.. an AM broadcast antenna tuned for 1010khz would be ~240ft in length, at quarter wave. FM broadcast antenna more like ~3ft.
I just got a 2012 Gen 3 and I get a lot of hisses from my satellite radio option. I did note the SAT comes in at a much greater volume than FM. Perhaps a better antenna?
the volume of audio doesnt really correlate when it comes to digital satellite radio.. however, I too have the same problem with the audio volume.. its pretty annoying... i'm also get plenty of FM audio reception, but don't get great HD-FM audio.. and when HD audio goes in and out, its really disrupting to listen to..