I checked this on my 2005 Accord EX-L/Navi. I selected a variety of FM
stations, including some that were weak. No difference whether the
rear defrost was on/off. I do note that the AM/FM antennas and the rear
window defogger connect to the "Window Antenna Coil" (page 150-2 of the
Electrical Troubleshooting Manual). This unit has a power input (from
the audio unit) so I assume it is an RF amplifier.
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