|Jul14-09, 04:53 PM||#1|
Which frenquency would a frequency counter count if its connected to an antenna that is recieving several frequencies close to each other in amplitude?
|Jul14-09, 06:22 PM||#2|
A frequency counter generally works by counting zero-crossings (or trigger level crossings in a more general case). What do you get if you add two sine waves of similar frequencies? What happens to the zero crossings? (Hint -- sketching it out may help)
|Jul15-09, 10:48 AM||#3|
What happens is that you get an unstable display. It may give a jumble of numbers or just the MHz part of the number might be OK and the rest is a jumble of different numbers with each count.
The counter sees a waveform that includes a beat pattern between the signals. So, sometimes the counter gets nothing from either signal because they are cancelling each other out. If this happens they won't cause the counter to count at all or to only count some of the pulses that should have been counted.
The counter uses a gating process to count so it all depends on how many usable pulses it gets in each gating period.
Generally, it is bad to have more than one signal coming into a counter.
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