Software-Defined Radio Kit

Think of a software-defined radio as similar to a radio tuner like the one on your car. It can analyze incoming radio waves of a user-selectable frequency and output this information in a variety of ways. We will be using this particular kit to pick up transmissions from satellites as well as listen to people talk on the air.

The actual software-defined radio (SDR) is a small dongle that plugs into a USB-A port on a computer. Also included in this kit are all the antennas, mounts, and cables necessary for all the projects using the SDR. This software-defined radio is shown in Figure 1-1.

Microcontroller (Arduino Uno)

The topic of microcontrollers is explained more in Chapter 6, but for now you can think of them as miniature computers. We will use this particular microcontroller to interface with the radio module. Such a microcontroller is shown in Figure 1-2.

Radio Module (NRF24L01)

This radio module is what actually takes the data from the microcontroller and sends it via radio waves. It’s easy to send data between these radio modules, and they’re inexpensive, so they make great modules for educational purposes. The actual module itself is shown in Figure 1-3.

Male to Female Jumper Wires

Battery Pack

We’ll use a battery pack to power one of the transceivers used in Chapter 6. This allows you to move it around and observe how the signal changes! This battery pack requires six AA batteries—if you don’t have any AA batteries, you will need to purchase these as well. The battery pack is shown in Figure 1-4.

Handheld Transceiver (HT)

This piece of hardware allows you to receive and transmit on amateur radio frequencies. Without the proper license, you are limited to receive functionality only; transmitting is against the law. We will go through the process of obtaining an amateur radio license later on in the book. This particular radio is extremely common due to its low cost and solid performance. This radio is enough to talk to amateur radio operators in your community or bounce messages off satellites to talk with individuals over a thousand miles away. This radio is shown in Figure 1-5.

Dualband Satellite Antenna

This is the directional (high-gain) antenna that we will later use to communicate with satellites. Rather than use the antenna in the mounted configuration shown in Figure 1-6, you’ll hold it in your hand and follow a satellite across the sky with it as you communicate with the satellite. When ordering this antenna, make sure you select “UHF Connector” as the connector type at checkout.

BaoFeng Programming Cable

This cable (shown in Figure 1-7) enables you to upload channels from your computer to your radio. It is possible to program channels without it, but your life will be much easier with the cable! There are cheaper cables available online, but this is the only official one. Because it’s official, it’s very easy to find drivers for the cable, so I highly recommend purchasing this one.

UHF Male to SMA Female

SMA Cable

SMA Female to Female

Cellular

Cellular networks, the namesake of cell phones, enable your smartphone to connect to the Internet and make and receive calls. Cell networks utilize immense amounts of communications infrastructure, such as the cell tower shown in Figure 1-9, to deliver packets of information to and from cell phones.

All cell phones have external antenna bands that enable them to communicate with cell towers. Antennas, as will be discussed later, are a device’s interface between electrical signals and electromagnetic radiation. A typical cell phone can connect with cell towers upward of a few miles away. Cell networks, or specifically the portion of the network that delivers data services, are a form of wide area network (WAN). Unsurprisingly, they get this designation as a result of covering a relatively large area with network coverage.

Wi-Fi

Wi-Fi is perhaps one of the most well-known communications protocols in existence. The word Wi-Fi is a trademark of the Wi-Fi alliance—its logo is shown in Figure 1-10.

Wi-Fi is actually a collection of wireless networking protocols, providing medium-range data services to and from a wired Ethernet connection. Wi-Fi is the fastest wireless communications protocol available for many consumer devices; it supports transmission of over 1 billion bits per second. Wi-Fi is a form of wireless local area network (WLAN). It does not get the designation of being a wide area network (WAN), as Wi-Fi is only designed to support a limited number of devices at a very limited range. Wi-Fi transmissions operate at a different frequency than those used for cellular, so Wi-Fi and cellular cannot share the same antenna on a device.

Bluetooth

Bluetooth is another well-known trademark describing a collection of wireless communications standards. Bluetooth is primarily used in connecting a central device such as a phone, tablet, or computer to a number of peripheral devices such as smartwatches, headphones, and other accessories. Bluetooth utilizes relatively little energy to transfer data, making it a popular choice for battery-powered devices. Due to its low power, Bluetooth can only operate across distances of a few tens of meters. This range limitation is why Bluetooth is designated as a personal area network (PAN). Bluetooth uses the same wireless frequencies as Wi-Fi, so the two oftentimes share an antenna.

GPS

GPS, as it is commonly used in conversation, is a colloquialism for any navigational device or system. However, GPS (short for Global Positioning System) actually refers to a specific satellite-based navigational system operated by the US government. GPS is a one-way communications system; GPS receivers do not send data back to the navigational satellites that make the system work. A GPS satellite is shown in Figure 1-11.

GPS receivers use the signals from a minimum of four satellites to pinpoint the device’s current location. GPS satellites emit time signals, and the receiver uses the time difference between received signals to calculate its distance to each satellite. The GPS receiver then solves an algorithm that yields its coordinates. GPS is a service of the US military, which reserves the right to disrupt or disable GPS to protect national security. As such, many other countries have their own satellite-based navigational systems. Most GPS receivers also include support for these other navigational systems to improve accuracy.

Marine Radio

Maritime radio communication is a very common example of a direct, long-distance radio link. Ships utilize predetermined frequencies, or channels, to communicate with one another. These channels lie in the VHF band of frequencies, which will be discussed later. The International Telecommunication Union (ITU) regulates channel allocation and use. Every large vessel—and practically every medium and small seafaring vessel—is equipped with a VHF antenna and radio designed to operate at marine frequencies. An example of such an antenna is shown in Figure 1-12.

Marine VHF radio is almost entirely voice based and can be used to communicate over distances no greater than 100 miles under normal conditions. Predefined channels exist for common tasks requiring communication, such as distress signals, port operations, ship-to-ship communications, and more. More sophisticated implementations of marine VHF radio support features such as text messaging and automatic ship identification.

Amateur Radio

Amateur radio will be discussed in great depth in subsequent chapters, but for now it’s worth mentioning in the context of long-distance communications. Amateur radio can best be described as an international group of individuals interested in radio. Amateur radio operators, or hams, use specially allocated frequencies to communicate with one another. Such communications can be between individuals separated by everything from a few miles to a few continents, depending upon hardware configuration. An example of amateur radio hardware is shown in Figure 1-13.

Satellite Data Services

For many locations away from population centers, a satellite link is the only possible means of communication with the outside world. Some satellite data services provide small, portable devices with a low-data-rate connection. Satellite phones and portable communications devices use such networks. Other satellite data networks provide large, fixed sites with a high-data-rate connection. Satellite Internet and TV rely on these types of systems. See Chapter 10 for a more in-depth description of these networks.

Deep-Space Communications

Radio is the only option for space missions to send data to Earth and receive communications from Earth. Most space missions are equipped with two types of communications systems: a highly directional antenna that supports long-distance communication but requires precise aiming (see Figure 1-14) and an omnidirectional but shorter-range system. Massive radio dishes on Earth receive the transmissions from various missions and relay the transmissions to mission operators.

AM and FM Radio

We will discuss AM and FM radio in greater depth in other parts of this book, but for now it’s worth mentioning what they are and how they work. AM, or “amplitude modulation,” and FM, or “frequency modulation,” are two means of encoding information on top of a radio wave. AM and FM have become colloquially associated with music and voice broadcasts of a certain frequency band, but know that they are general techniques. “AM radio” or “FM radio” is used to specifically denote the music and voice broadcasts that you’re likely familiar with.

AM radio and FM radio each use different frequency bands and have their own strengths and drawbacks: FM radio transmits a higher-bandwidth signal than AM radio, but cannot propagate as far as AM radio.

Broadcast Television

Broadcast television is one of the few applications of radio communications technology that has declined in usage in recent years. The frequency ranges allotted to broadcast television are huge and occupy a very useful place in the electromagnetic spectrum. Many governments have been repurposing these frequency allocations and are auctioning them off to telecommunications companies to deploy cellular networks on the frequencies.

Despite these changes, broadcast television signals are still common. Signals were originally broadcast in an analog format, but most countries have switched over to digital transmissions. Areas lacking in telecommunications infrastructure benefit from broadcast television’s ability to provide television to far away and isolated locales. Many of the large antennas that you see on top of structures, such as the one in Figure 1-15, are or once were utilized to receive broadcast TV signals. Cable television has surpassed broadcast television in many places, as it offers more channels at a higher quality.