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Most modern receivers have a circuit concerned with automatic signal gain control, or AGC. A great number of consumer receivers have no way of turning this feature off. In FM receivers there is also the automatic frequency control. When these 2 circuits work in tandem, actual signal variations are covered up in the receiver. This interaction makes the signal strength indicators in most receivers only a approximation of the signal strength.
Additionally, if the stereo decoder in an Fm receiver is switched on and off momentarily, perceived signal strength by audio quality can also be very misleading.
AGC circuits in AM, FM and TV were developed to provide the receiver’s detectors and demodulators a constant signal level so that consumers were not bothered by the rise and fall of the received signal.
“Ghosting” is caused by multipath signal distortions in the receiver. The primary signal is followed by a short delay of the reflected signal causing a secondary image on the TV screen. The same kind of audio multipath distortion can be introduced into FM radio receivers as well.
And finally, a vertical oriented antenna would have to “heel over” by 30 degrees or more to override the effects of the receiver AGC or to decrease the perceived signal strength. That kind of “list” would sink most small power vessels depending on the freeboard of the vessel. There are several variables at work here, so actual world and anecdotal evidence is what counts here. Most likely the only people who would notice are the folks who are already listening to a very noisy signal already.