In most receivers, the internal oscillator runs at a different frequency than is being received, with a fixed offset. That fixed offset is determined by receiver architecture. For example, a typical superhetrodyne AM broadcast receiver, tuned to 740 KHz AM, might run its oscillator at 1195 KHz AM. The amplified antenna signal and the oscillator signal are combined to make a signal that contains outputs at the sum (740 + 1195) KHz and difference (1195 - 740) KHz. They are then filtered around 455 KHz to eliminate the other signal. This frequency is called the IF or intermediate frequency. So the bottom line is - a receiver likely can and will emit on a different frequency than you are listening to. Some modern receivers have IF's circa 5.5 MHz, as I recall...
Slashdot Mirror
Check these out.
I remember reading "The Education of T.C.Mits" as a teenager.
(T.C.Mits is sort of an acronym for "The Common Man-in-the-Street").
Lillian Lieber's other books are likely also wonderful.
http://pauldrybooks.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PDB&Product_Code=190&Category_Code=
The Einstein Theory of Relativity
Infinity
Mits, Wits & Logic.
In most receivers, the internal oscillator runs at a different frequency than is being received, with a fixed offset. That fixed offset is determined by receiver architecture. For example, a typical superhetrodyne AM broadcast receiver, tuned to 740 KHz AM, might run its oscillator at 1195 KHz AM. The amplified antenna signal and the oscillator signal are combined to make a signal that contains outputs at the sum (740 + 1195) KHz and difference (1195 - 740) KHz. They are then filtered around 455 KHz to eliminate the other signal. This frequency is called the IF or intermediate frequency. So the bottom line is - a receiver likely can and will emit on a different frequency than you are listening to. Some modern receivers have IF's circa 5.5 MHz, as I recall...