How much work is it to modify an am radio to receive low frequencies 10 to 200 hertz ?
Less effort than running the 300,000km antennae wire.
That frequency is very specialized technology are you trying to communicate with submarines or miners?
I want to pick up rf signals from power lines and appliances.
how are the rf signals different from magnetic fields.?
The bandwidth of the IF filter in the radio would be 10kHz so it makes no sense.
Power lines and appliances don't emit RF at line frequencies (ie 60Hz)
They do emit some higher frequency RF which will cause interference on a radio.
To detect the magnetic field you would need a search coil and a sensitive voltmeter or oscilloscope and have to be pretty close.
A low pass or tunable band pass maybe with active filters and a scope unless you go the digitial signal processing root but you will have to have some sort of display whatever or meter or rising and falling tone.
A very low frequency spectrum analsyer would be possible. You need a very small IF bandwith.. 0.1 Hz.. ish
I don't think there is a much of a field from power line because they are balanced. The field produced by one conductor is cancelled out by another because the current is flowing in opposite directions. There is high frequency mush due to corona effects.
It's not worth to modify an AM radio to an ELF receiver. It would be simpler to build one from scratch using a couple of op-amps and an inductance gyrator for the tuner. Even could pick up signals from US and Russian military submarines at 75 and 82 Hz respectively.
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