Welcome to lesson 17, Common Modes of Operation.
Setting the mode of operation on your radio is like telling your radio what language to speak.
And one of the exciting things about ham radio is that there are various different modes you can use, like FM, SSB, CW, or even digital modes like FT8 and DMR. Each mode of operation has different advantages and use cases.
In this lesson, we’ll cover some of the most common modes of operation and discuss how they are used.
Common Modes of Operation
FM
When you first get your ham radio license, your first contact will probably be using the FM mode, which stands for frequency modulation. FM is the most common mode used for handheld voice communications and for VHF and UHF voice repeaters.
SSB
SSB, which stands for single-sideband, is another popular mode used for transmitting your voice over amateur radio, but it is better for long-distance contacts than FM.
FM is like a shotgun, providing high-quality audio at short ranges. SSB is like a sniper rifle and is the undisputed king of long-distance voice contacts.
SSB is the most common mode for voice communications on HF. SSB is also used for long-distance (weak signal) contacts on the VHF and UHF bands.
Another disadvantage of FM compared with single sideband is that only one signal can be received at a time. When operating SSB, you can often hear multiple voices piled up or mixed together, allowing you to hear multiple people talking at the same time. We call this a pileup. On FM, the strongest signal wins out, and you’ll usually only hear the person with the strongest signal.
Single sideband is actually a form of amplitude modulation, aka AM, as in AM radio, but it is designed to be much more efficient.
There are two different types of SSB – Upper Side Band, aka USB, and Lower Side Band, LSB.
- In the upper sideband, your voice data is added above the carrier frequency
- On the lower sideband, your voice data is added below the carrier frequency
So if you want to communicate with someone on SSB, you have to make sure you are both set to the same sideband, either USB or LSB.
To make it easy, ham radio operators created a gentlemen’s agreement to decide which sideband to use.
For frequencies below 10 MHz, we use the lower sideband. This includes the 40m band, 80m band, and 160m band. But as a Technician, you don’t have access to those bands yet.
For frequencies above 10 MHz, we use the upper sideband, which includes 20m, 15m, and 10m, as well as VHF and UHF frequencies. As a Technician, you’ll have access to use SSB on 10m as well as VHF and UHF.
So when the exam asks which sideband is normally used for 10-meter HF, VHF, and UHF, the answer is Upper sideband.
Most radios will switch from upper sideband and lower sideband automatically depending on your frequency, which makes it super easy.
CW
Let’s talk about CW. CW is another name for a morse code transmission. Morse code is the oldest form of radio communications and is still in use today.
SSTV & Amateur Television
You might be surprised to learn that you can send images and video over ham radio.
SSTV, aka slow scan TV, is the most popular way to send images, and you can even receive images from the International Space Station with just a basic handheld.
Amateur television is sometimes referred to as “Ham TV”, which is sending live video and audio over ham radio. It could be everything from transmitting video of your shack, video from drones or weather balloons, and Ham TV is even installed on the International Space Station, as well, which shows a live feed from the ISS.
One way to send television over amateur radio is via NTSC, which is a term you need to know for the exam.
NTSC is an analog fast-scan color TV signal, that can be used for HamTV.
Bandwidth Comparison of Common Modes
Each different mode of operation uses a different width of frequency spectrum, called bandwidth.
A narrower bandwidth means the signal is more efficient and uses less spectrum. But, for sending more information, sometimes more bandwidth is needed.
CW has the narrowest bandwidth of all the ham radio modes, because it is a very simple transmission of a single tone of dits and dahs. The approximate bandwidth of a CW signal is only 150 Hz, making it extremely efficient and great for weak-signal communication.
Next up is SSB. The approximate bandwidth of a typical SSB voice signal is 3 kHz.
SSB has a narrower bandwidth than FM, the other common voice mode.
An FM voice signal on VHF repeaters has an approximate bandwidth of between 10 and 15 kHz.
To send AM fast-scan TV transmissions, aka Ham TV, you’re going to need more bandwidth to carry the extra information.
The approximate bandwidth of AM fast-scan TV transmissions is about 6 MHz.
Lesson Recap
Let’s review. In this lesson, you learned about the most common modes of operation in ham radio.
- FM, which is commonly used for handhelds, local communications, and repeaters
- SSB, which also transmits voice like FM, but has a smaller bandwidth and is more suited for long-range communications on HF, VHF, and UHF
- CW, aka Morse code
- And HamTV, which commonly uses NTSC, an analog standard for fast-scan TV.
We also reviewed the bandwidths of these common modes
- CW is the narrowest, with a bandwidth of just 150 Hz
- Next is SSB with a bandwidth of approximately 3 kHz
- FM has an approximate bandwidth of between 10 and 15 kHz
- And the largest is AM fast-scan TV at 6 MHz.
