Most amplifiers filter out higher frequencies that can cause interference, and they often filter out DC to protect the speakers from DC signals. It's easy to built an audio amplifier that goes DC to to 1MHz or higher, but most don't. And because radio waves are an analog phenomenon, the input must be analog if you want to receive radio signals with it, and the output must be analog if you want to transmit signals with it.ДЈ84khz sample rate on both input and output, and with both the input and output being analog, means I could have sinewaves with frequencies anywhere between 0 and 192khz,You're right about the Nyquist theory, but there's no guarantee that an audio DAC or ADC is going to go that far above the audio range. Because maximum usable frequency is limited to one-half of the sample rate, the higher the sample rate, the better.

To turn any sound card into a radio receiver, just connect a straight wire to the left channel of the line-in or microphone-in port. To turn any sound card into a radio transmitter (with the maximum usable frequency being limited to half the sample rate), just connect a straight wire to the left channel of the line-out or speaker-out port. So being able to transmit and receive in this range would be VERY interesting. However exotic and/or experimental radio transmitters are often used in this range (for example underwater radio communications), and possibly radio signals generated from natural phenomenon. This is well below the lowest frequency used for ham radio, and in fact is well below the lowest frequency used for conventional AM radio broadcasting (or any other type of normal radio communications). ELF means Extremely Low Frequency, VLF means Very Low Frequency, and LF means Low Frequency. This would be very useful for radio frequency experimentation (both transmission and reception) in the ELF (0 to 3khz), VLF (3khz to 30khz) and a limited portion of LF (30khz to 300khz, or in this case limited to a maximum of 192khz). 384khz sample rate on both input and output, and with both the input and output being analog, means I could have sinewaves with frequencies anywhere between 0 and 192khz, either on the input or output.

Is there any sound device that has 384khz sample rate for both input and output, and that has both the input and the output being analog (not digital) audio?ДЄnd now an explanation for why I'm hoping that such a device exists.

Vlf receiver sound card