In ham radio the term mode has at least five distinct meanings. It’s confusing for even experienced hams so we’ll try to tame some of this madness.
If you’re a new ham with a handheld or mobile transceiver to talk on the local repeater, mode doesn’t mean much to you. Your basic radio has no mode controls because it can only do one thing. In this case you are operating in voice mode using frequency modulation (FM). Guess what? These are the first two—and most important—of the definitions of mode. These are operating and modulation modes.
Below we will explore the five different contexts for mode found in US license exam questions:
Operating Mode- The most basic definition of mode; a general category of radio transmission and reception. There are three or four operating modes, depending on how they are categorized. The common three are:
- CW (continuous wave), typically for Morse code (radiotelegraphy)
- Radiotelephony (phone), a fancy term for voice communications
- Digital, where data is exchanged over the air, requiring computers or machines to interpret signals
For logging and awards these three categories are CW, Phone, and Digital modes. The ARRL Logbook of The World (LoTW) adds a fourth category: Image. Collectively these 3 or 4 are known as mode Groups.
Modulation Mode- Modulation is the means to impress information on a radio signal. It’s how a circuit puts our voice onto the radio signal through a microphone. There are different forms (modes) of modulation which can be employed within each basic operating mode.
For example, typical modern HF transceivers support voice modes using AM, FM, and SSB modulation modes. There are a few flavors of CW and dozens of digital modes (and the list keeps growing). Just look at that mode group list link above.
To further complicate matters we now have both traditional analog modulation for phone (voice) signals, and digital voice modulation as well. Many digital modes simply modulate a SSB waveform using specific tones to represent data characters. We live in an era where computers and radios are really working together to do amazing things.
Operating and modulation modes are hard to separate. In fact, they sort of overlap and mash together. Context of the discussion is key here; often it doesn’t really matter.
These two also play a role in the ITU classification of RF signals. Refer to Types of Radio Emissions link. Hams may occasionally log their mode according to this or a similar scheme.
Why do so many operational and modulation modes exist? It’s largely for historic reasons as technology and electronics have advanced over the years. In the earliest days of radio, only radiotelegraphy existed. Mode had no meaning as CW was the only possibility. Then came voice technology and a second operating mode was born. Going from original AM to SSB, we then had modulation modes, adding FM as an improvement later. Digital mode entered the scene after voice once people discovered they could encode audio signals to represent data; computer technology has made the digital mode wildly successful, if less personal, in recent years. Image modes have been around since the early days of television but here again, computers have made them better and easier.
One other reason for different modes is efficiency, particularly in voice modes. Bandwidth of different modulation modes varies significantly. There is a trade-off between signal quality and efficiency; some modes were developed to reduce bandwidth.
Propagation Mode- Any of several ways for RF signals to travel from transmitter to receiver may be termed a specific propagation mode.
Satellite Mode- Amateur satellites are essentially ham radio repeaters in Earth orbit. Unlike their terrestrial brethren most satellites are very small and cannot support the size and weight of the usual mono-band duplexer needed to separate the offset frequencies. Instead, they operate on different bands, one for up-link and the other for down-link so that there can be no interference or damage from transmit (strong) to receive (weak) signals.
In this context the term mode applies to the up-link and down-link bands, typically UHF and VHF (U/V).
Hams of all US license classes can play with amateur satellites. We need only one or two FM radios and an appropriate handheld antenna to aim at the satellite as it passes in view.
Split Mode- Split operation is commonly used by rare stations to help sort out the large number of hams trying to reach them. This is known in ham-speak as a pileup when dozens of hams (hounds) try to make contact with a rare or unusual station (fox). The fox will transmit on one frequency for the hounds to hear and listen on a slightly different range of frequencies. Many modern transceivers support split mode with two variable frequency oscillators (VFOs), as do (naturally) independent transmitters and receivers.
Even the US Technician licensee has privileges to use different modes. Let’s say you have a multi-mode radio now. Unlike your HT, this one will have a mode select control. Here you can choose which operating/modulation mode you want to use. Common selections in modern transceivers include AM, FM, CW, LSB, USB, and digital mode.
Hopefully this helps you get a handle on these five meanings of mode. The good news is that in most cases the context of discussion makes it clear.
A future topic will look at details of voice modulation and squelch.
Some useful links:
List of amateur radio modes -Wikipedia
Loads of Modes -Ham Radio School
Modes and Systems -ARRL
Modes, Modulations, and Digital– Hackaday article