General Question

Jonathan_hodgkins's avatar

Analog & Digital communications?

Asked by Jonathan_hodgkins (678points) May 5th, 2015

I am doing some research on the difference between digital and analog radio communications used by law enforcement and first responders.

What is the difference between the two systems and what are the benefits of each?

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6 Answers

Bill1939's avatar

I think that digital signals interfere less with each other so more channels are possible, however analog signals can be received over longer distances.

dabbler's avatar

All radio is basically analog but ‘digital’ radios encode the message/signal on the transmit end and decode on the receiving end.
Digital radios can be more robust while the carrier signal remains strong because if the digital stream gets through it can be reconstructed to a form very close to the original.
Received analog signals can be distorted by anything that can affect the carrier, but the analog signals can get partial information through in difficult situations where a digital signal is just lost.
I.e. analog radio degrades ‘gracefully’ while digital either works or does not work.

LuckyGuy's avatar

Digital radio, like digital TV, either works or it doesn’t. There is no weak, distorted, ar static filled audio. The received audio is perfect. However…. if the first responder is in a signal denied area the digital radio will not work well. The audio will drop out. analog radio will get weak with static but some intelligible information can be recognized.
Digital has the ability to incorporate higher security algorithms at a low cost. Analog can do the same but it is a little more difficult. Secure analog has been around, but not popular, for decades. Back in 1982 the President’s phone (at the time one of the most secure on the planet) had frequency hopping and spread spectrum – the same technologies used in 10 year old cordless phones.

Strauss's avatar

The technical difference between a digital signal and an analogue signal gets back to the basics of electronics. All electronic signals (as well as all sounds) are by nature analogue, based on some variation of the sine wave.

A digital signal is an approximation of the sine wave, often indistinguishable by the ear, often referred to as a digital sine wave.

As far as the pros and cons, @LuckyGuy and @dabbler have just about covered them for your application.

Digital signals are easier to use with higher security algorithms.
If a digital signal gets too weak, it just stops, whereas an analogue signal will actually sound like it’s fading.

ARE_you_kidding_me's avatar

It goes much, much deeper than this. Digital communication using rf opens up a whole new world of packet communications, spread spectrum, various forms of multiple access, compression, trunking such as p25 as well as other advanced modulation techniques. All of your bluetooth, wifi, zigbee and most cellular are also digital radio.

Strauss's avatar

@ARE_ you_kidding_me You’re absolutely correct. There are advanced degrees of study in electronics that cover the subject in far greater detail than we will right here; that’s why I kept my technical explanation short and sweet, then moved on to the part about …as used by law enforcement and first responders

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