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4

ALC, in general, stands as an abbreviation for Automatic Level Control, which is a class of circuits designed to back-feed information about the output signal to an amplifier. The goal is to change the parameters of the amplifier so that a clean output that remains within certain parameters is attained. In normal HF transceivers, such a circuit will most ...


3

The dynamic range of (shortwave) received signal strength varies from noise equivalent field strength (in the order of 250 nV/m in 3 kHz SSB bandwidth) to 1 mV/m (for radio ham transmissions via the ionosphere). Local signal can go over 1 mV/m. In short: dynamic range is in the order of 72 dB. AGC doesn't have to cover that range, but 50 dB is "nice to ...


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ALC limits the the input power to the power amplifier (PA). Overdriving the PA would be bad: it might overheat, or exceed the voltage or current ratings of the components, eventually, or sometimes immediately, damaging the PA. Or it might just cause a lot of distortion and spurious emissions. If the radio has adjustable output power, often this controls the ...


1

There's a huge variance in signal levels — the lowest signal that's readable above the noise floor and the strongest signal that won't overload the receiver are probably at least 60dB apart. To get that into a comfortable listening range without AGC, the operator has to adjust the receive level. Maybe that doesn't sound like a big deal (can't you just set it ...


1

IMD will respond more to attenuation as the receiver will be operating in a more linear region. This is your best bet for detecting IMD: If you add 3 dB of attenuation (or reduce gain by 3 dB) and you see some signals or the noise floor go down by more than 3 dB, you've significantly reduced IMD. There is another way to determine if attenuation should be ...


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On some (most?) receivers, if the RF gain is turned up too high, intermodulation distortion increases due to increasing non-linearities (maybe even clipping, etc.) I'd argue that's all receivers, even, since that's exactly what "turned up too high" would imply. You get a non-linear effect, and that always leads to intermodulation. If that doesn't ...


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