Digital Overview

What is Digital communications?

We all grew up in the analog communications world, choosing between Amplitude Modulation (AM), Frequency Modulation (FM), or if you were a Ham, Single Side Band (SSB) modulation.  All three were similar techniques to send primarily voice or music.  AM would adjust the amplitude (strength) of the transmitted carrier at the voice frequency.  FM would slightly vary the frequency of the transmitted carrier at the voice frequency.  SSB is a special case of AM the uses half the bandwidth, poor for audio quality but good for DX.

Digital takes a different approach that uses pulses of energy, all the grandchild of Morse Code.  It is easier to detect if a carrier is transmitting (a digital “1”) or (a digital “0”) than detecting subtle changes in amplitude or frequency.  Morse Code is slow, typically less than 30 words per minute, but served us well since Marconi’s first transmission in 1897 because that was the speed that humans can send or understand.  Modern microprocessors changed everything.

Today, the processing power in even the simplest of ham radios can turn pulses on and off at blazing speeds, and they can control the personality of individual pulses, pulse spacing, groups of pulses, and more.  This makes it possible to send not just voice or music, but expanded data options such as text, images, location, internet voice and more, all at speeds that Marconi couldn’t even imagine.  The engineering and radio guru’s are constantly inventing and tweaking new ways of sending digital information based on some fundamental techniques.

• Simple Morse Code.  The transmission (pulse) is on or off.  The most basic form of digital communications, and still very effective.

• Pulse position modulation (PPM).  Changing the positions of pulses relative to each other, or relative to a time standard.

• Pulse width modulation (PWM).  Making pulses, or spaces, wider or narrower.

Many variations of these techniques are implemented under many names, each with their own merits. Some examples are:

• Phase-shift keying (PSK)

• Frequency-shift keying (FSK)

• Amplitude-shift keying (ASK)

• On-off keying (OOK), the most common ASK form

• Quadrature amplitude modulation (QAM), a combination of PSK and ASK

• Continuous phase modulation (CPM) methods

• Continuous envelope 4-level frequency modulation (C4FM)

If that wasn't enough, different manufacturers implement digital modulation schemes under their company terminology such as DMR (Motorola & others), D-Star (Icom & Kenwood) or System Fusion (Yaesu).  

. . . But do we care?

Pros and Cons of Analog Radios (VHF/UHF)

Pros

• Cheaper: When comparing the cost of analog vs digital radios, analog radios are usually less expensive, which is perhaps their biggest advantage and makes them more appealing. Although some experts claim that this price differential will be null in a few years when digital products become more affordable.

• Inter-Operable: Because they have been around forever, there are many accessories and add-ons available for analog radios. Even new analog radios work with older equipment and accessories.

• Easy to Use: They are a popular choice because of their simplicity and user-friendly interface.

• Coverage: In areas where users may be moving in and out of coverage, (search and rescue, wilderness, or outdoor pursuits) analog radios may work better.  They can provide more coverage options if the signal is weak.  However, ham operator tests have found the range is similar, more or less depending on modulation techniques and Mother Nature.  Obviously neither will work beyond signal range.

Cons

• No Group Chats: Most analog radios are only capable of one two-way conversation at a time, on a repeater, meaning you can only have one unique conversation at a time.

• Older Technology: While devices can be upgraded, the technology cannot.  Some device aspects of analog radio can be upgraded; at the end of the day, analog radios still operate using the same simple technology.

Pros and Cons of Digital Radios (VHF/UHF)

Pros

• Ability to send far more varied forms of data.

• Group Chat:  Digital radios are capable of more than one unique conversation on the same repeater allowing two conversations to happen simultaneously with one not hearing the other.

• Noise Canceling Technology:  Background noise can be reduced to make communication on digital radios clearer.

• Evolving Features and Upgrades:  New software upgrades are consistently offering increased performance and new features.

• Better Battery Life:  Digital radios typically have 30-50 percent more battery life than analog radios.

• More Secure:  Digital can offer end-to-end AES 256 encryption to keep your sensitive communications secure.  Although encrypting amateur transmissions is not allowed by the FCC.

Cons

• Interface Learning Curve:  Digital products are more advanced and more complex than analog radios, so they aren’t as user-friendly.  It will take more time to get used to it, and perhaps more computer skills to learn all the new features.

• More expensive: Digital radios are typically more expensive than analog options because the technology is more advanced, and they have more expansive features.  However prices are dropping as the technology becomes more mature.

• Dropped Signal:  Digital signals don't get weaker.  They are there - or they are gone.