Quote: From time to time I come across the concept of analog and digital devices. And although the definition can be found on the Internet, I am not able to define which devices are analog and which are digital. Can you provide any simple way to classify the device into one or the other group?
The problem is that the world is analog, a device that is to digitally process signals from the outside must also have an analog part. The word digital is often overused, it appears in advertising slogans and even company names, e.g. "digital quality" "digital pol.at". Most people associate analogue with a vinyl record or a cassette tape or VHS, and digital with a CD / DVD, etc., hence the idea of digital over analog, but the "digital" audio amplifier, i.e. class D, still gives way to analog, and speakers and microphones are still analog because no way has yet been invented to digitally convert the data stream into air movement.
As an example, I can compare analog and digital filters, an analog filter is an electronic system designed to separate a certain frequency band, the better selectivity we require from the filter, the higher order the filter must be, which means that there are more and more elements in the system and the requirements for the accuracy of these elements are more and more difficult to be fulfilled, therefore it is impossible to make an ideal filter.
A digital filter is an algorithm that multiplies and adds (before that we have to convert the signal into digital form), if we have a fast circuit that will calculate it, we can build a filter much more complex than the analog one and much better selectivity, it works great at low and medium frequencies, but If we wanted to filter frequencies of a few GHz, the requirement for a digital system several dozen / hundred times faster becomes very difficult to meet, then we can use analog filtering that is easier to implement (this is how digital radio is often realized, analogue start, then conversion and digital rest)
How to determine if the radio is digital? As a user, you have no chance, the degree of "digitization" can be very different, a few dozen years ago a PLL loop was introduced to completely analog radio, the loop is analog but the frequency can be set digitally, there are completely analog radios that receive digital transmissions, even Morse code can be included for digital broadcasts.
But SDR (software defined radio) is something more, a radio in which demodulation takes place digitally, completely digital radio is still a rarity, although theoretically, to receive low frequencies, you could connect the ADC directly to the antenna and do the rest digitally, for now amplification and preliminary filtering a sometimes the conversion is easier and better to do analog.
It often happens that the "digital quality" of digital equipment is mainly determined by the analog part - eg in digital cameras it is the analog lens and the analog matrix that decide.
. Currently, we have mixed systems that facilitate construction and ensure the appropriate quality of processing. It's like having a 1Mx1M monitor with a diagonal of 24 "to observe the image from a distance of 1m. The human eye will not process that amount of data, so it is a pointless monitor.
