Archive for April, 2016

A Brief History of the Two-Way Radio

The two-way radio has come a long way from the days when you used to play with those walkie talkies you got for Christmas only to have them break or to lose interest in them before the following spring. Actually, the two-way radio has been around for more than a century, but technological advancements make today’s two-way radios a breed apart from what they started out as and what you played with as a pre-teen.

Then and Now: A Short History

From security to aviation to warehouses to schools and campuses, two-way radios, which can both transmit and receive, are used in a wide swath of different venues and occupations. Around the beginning of the 20th century, Swedish engineer Ernst Alexanderson developed the first high frequency generator that enabled the transmission of speech. Before the first World War, sailors were using radio transmitters and receivers on ships out at sea.

Australian policeman Frederick William Downie developed the first true mobile two-way radio for patrol vehicles in the early 1920s. In 1933, the Bayonne, N.J. police department launched two-way communications with its patrol cars, a marked improvement on previous one-way systems.

In the late 1930s, Motorola created and marketed the SCR300 walkie talkie, largely for use in the military by infantry soldiers. In 1944, Galvin Manufacturing Corporation installed Motorola radios in Yellow Cab Co. taxis in Cleveland, the first commercial FM two-way taxi communications system in the U.S. But in the generations since, two-way radios have evolved into more lightweight, compact communications devices that offer as few as two or as many as 14 channels for locations that consist of several different frequencies.

Staying within Radio Use Guidelines

Radio signals must follow a communication protocol and frequencies also have to follow the regulations that have been set so that they do not interfere with other frequencies. In the 21st century, two-way radios have become so streamlined and advanced that they’re as easy to operate as a telephone, with governing bodies like the FCC aiding in the process of providing seamless communication.

Add comment April 28th, 2016

A Must-Have Guide to Two-Way Radio Accessories

Using a two-way radio opens up a whole new world of communication possibilities for its users, and the range of accessories for two-way radios available at TechWholesale can make the experience even more exceptional.

Get the most out of your DLR digital two-way radio with a high-capacity 12-hour lithium battery that provides up to 12 hours of continuous use. Swivel earpieces are durable and comfortable, made for all-day use on business radios and designed with flip construction so that you can switch ears and stay comfortable through a long day of radio communication. Use your speaker without using your hands with a remote speaker microphone that clips to your shoulder and positions the speaker directly below the ear so it is unobtrusive, easy to use and functional.

Accessories can Add Functionality

If you have a whole team full of two-way radio users, a multi-unit charger consolidates the process of charging several units to just one outlet. Charge the whole radio, or just the lithium ion batteries. Stay connected without sacrificing safety with a lightweight temple transducer that can fit inside a hardhat or a helmet and converts audio to vibrations that get transmitted through the bones in your temple to your inner ear. This enables the user to hear the voice on the other end without blocking out the important sounds in a warehouse or work environment that are so critical to staying safe.

Keeping Your Two Way Radio At-the-Ready

Keep an RDX walkie-talkie on your hip with a spring action belt clip that attaches right to your belt, making it easy to reach for without having to fumble around. Protect your two-way radio with a hard leather carry case that is durable and convenient, snapping right to a belt or uniform and providing insulation to keep the phone safe from the dangers of the day on the sales floor or in a warehouse or factory.

Stubby UHF antennas for 4-watt RDX two-way radios are wearable throughout the day and are easy to install when replacing the longer and less convenient stock antenna that came with the radio. A headset with a boom mic enables users to keep their hands free while staying connected, comfortable and in communication with whomever they need to be.

1 comment April 25th, 2016

What is Frequency Hopping Spread Spectrum (FHSS)?

If there is anybody who hates the prospect of interceptions more than Peyton Manning or Tom Brady, it is anyone attempting to transmit radio signals and hoping to avoid narrow band interference and having their signals “picked off” the way a larcenous defensive back going for the pigskin does in a football game.

Keeping Your Transmission Safeguarded

If you want your radio signals to be less susceptible to interception, Frequency Hopping Spread Spectrum transmission is the way to go. Defines as “a means of transmitting radio signals by shifting a carrier across a number of channels with a pseudorandom sequence that the sending and receiving station knows beforehand,” Frequency Hopping Spread Spectrum (FHSS) is employed as a multiple access process in the Frequency Hopping Code Division Multiple Access transmission scheme. Repeatedly switching frequencies when transmitting a radio signal makes it harder to jam or mess with that signal by any agent with potentially malicious intent.

The Benefits of FHSS

FHSS provides several clear-cut advantages. First, the likelihood of narrow band resistance is slim with FHSS because an interfering signal gets relegated to the background with the spread signal. Second, when a narrow band receiver detects FHSS signals, the signals give the appearance of an increased level of background noise, making their interception unlikely because the pseudorandom transmission hopping sequence has to be known. Military radars are harder to target with FHSS than radars on a single frequency. Third, FHSS transmission signals cause very little interference, maximizing the use of the bandwidth so they can share frequency bands with a number of other types of conventional transmissions.

Reflections, noise and other external factors in the environment have a minimal influence on this technology, which is well-suited for installations that cover large areas where several co-located systems might be required.

When the military uses the FHSS Algorithm, it uses cryptographic techniques that encrypt communications and generate the channel sequence to be used during the communications session.

1 comment April 21st, 2016

How and When to Use a Throat Microphone

When noise is amped up to the max, a mic at the throat can be the best way to convey your own voice.

Pilots who have to communicate their messages in extremely noisy environments frequently use throat microphones. Unlike regular microphones, which pick up sounds via acoustic vibrations in the air, a throat mic attaches directly to the throat so that source of the audio input is the larynx itself. By doing so, the throat microphone conveys a vocal sound that is crystal clear, unimpeded by competing noise and easier to understand.

Understanding the Basics of the Throat Mic

A throat microphone, which filters out acoustical background noise, works by being securely fastened around the neck with transponders that rest on the throat. Also known as mic pickups, the transponders, which are usually used in pairs, make direct contact with the throat. A throat strap is fastened at the back of the neck, and one or sometimes two ear pieces are placed in the ear. It may take a little bit of trial and error to locate the perfect spot on your neck for the transducers to work optimally, since every neck has a unique shape and contour and everyone’s Adam’s apple is a different size.

Once the microphone’s output cable is plugged into the transmitting or receiving device, you’re ready to start communicating by using your throat with no “middle man.” The mic cable goes into the audio input port if you are plugging it into a computer or a cell phone or smart phone.

The PTT (push to talk) button is used to talk on the microphone. If you are using a wireless microphone, to receiving device should be tuned to the broadcasting frequency that is found either in the manual or right on the microphone’s box. The frequency of each throat microphone is unique.

1 comment April 18th, 2016

How to get the Most Range from Your Two Way Radio

One aspect of two-way radios that too often turn into a one-way ticket to disappointment is manufacturers that advertise an expected range that ends up not being attainable. Too often, a two-way radios actual range falls far short of what “optimistic” manufacturers trumpet in their literature and advertising.

Tips and Tricks for Extending Two Way Radio Range

There are, however, ways that you can often boost the amount of range you are currently getting from your two-way radio. For radios that support General Mobile Radio Service (GMRS) channels, which are land-mobile FM UHF frequencies designed for two-way communication over a short distance, make sure that you are actually using a GMRS channel rather than an FRS channel. FRS (Family Radio Service) channels are a two-way communications method designed to be used only over a very short distance and have a maximum output of 500 mW.

The Federal Communications Commission (FCC) does not allow transmission on an exclusive FRS channel at more than half a watt of power. Anyone’s radio using an FRS-only channel will transmit using only “low power” mode. The FRS-only channels are 8 through 14. Channels 15 through 22 are exclusively for GMRS, and channels 1 through 7 are shared by both FRS and GMRS.

Use high-power mode on your two-way radio, or else you will not achieve maximum range. Low-power mode cuts down on the amount of output power your radio is using. A battery that is not fully charged can also compromise a two-way radio’s range capability. A battery with a low charge results in a radio with less transmission power.

Bonus Tip

Two-way radios also have a monitor channel feature that allows users to check and see whether a channel is clear before transmitting. When this feature is enabled, the channel is opened and transmission signals too weak to be audible when the radio is in normal mode can now be heard, although often with a considerable amount of static.

Add comment April 14th, 2016

Air Band Radio Basics

No matter how high you fly, staying connected while you’re aloft is critical. Air band radios keep the lines of communication open for aviators as they are flying the friendly skies.

Employing VHF frequencies in the 108 MHz to 137 MHz range, air band radios, also known as avionic radios, serve as navigation tools and provide two-way communication for pilots. VHF air band channels are allotted by the Federal Communications Commission for the electronic systems used on aircraft. Unlike land-based radios, air band radios boast a much greater range since they are transmitting from air to air or from air to ground. Handheld air band radios of 5 watts have a much greater range than a ground-to-ground VHF or UHF two-way radio that is also 5 watts.

Understanding the Band

At the higher end of the band, COM channels are programmed for voice communication and have frequencies ranging from 118.000 MHz to 136.975 MHz. For navigational help, NAV channels are on the lower end of the band with assigned frequencies from 108.000 MHz to 117.95 MHz. These frequencies are split into 200 narrow-band channels of 50 kHZ.

A system of short-range beacons called VOR (VHF Omnidirectional Range) has become the global standard for navigators and helps pilots in knowing their position so that they are able to stay on course during a flight. NOAA weather alerts and updates also appear on VHF air band radios.

The Many Forms Air Band Radios Take

Air band radios can be handheld, panel mounted or ground station-based. Handheld air band radios look much like portable handheld land mobile two-way radios. Panel-mounted air band radios, like a mobile radio in a car, mount into an aircraft’s cockpit. Ground station avionic radios mounted in a vehicle or an office operate on the ground. Incidentally, the band just below the Civil Aviation Band (108 to 137 MHz) is the universally recognized FM radio band everyone listens to in their cars or at home that ranges from 88 MHz to 108 MHz.

Add comment April 11th, 2016

How to Use the Vox Feature on Two-Way Radios

Businesses that depend on two-way radio use are getting a hand from a technology advancement that doesn’t even require the use of hands. Voice-activated transmit, commonly known as VOX, is a communication capability that enables your staff to speak in the direction of the mic of a two-way radio. When they do that, the VOX-enabled radio mic takes care of the rest. When choosing a two-way radio for your business, always weigh all the available features.

What Happens First?

As soon as someone speaks into the mic of your two-way radio, the radio will automatically begin transmitting. Most two-way radios have two methods of transmitting: either by manually pushing the button to talk (PTT); or, when VOX mode is activated, by simply talking, and allowing VOX’ sound-activation technology to work its magic. VOX type headsets always keep the microphone active, so the radio will automatically start transmitting when you speak. It frees the user of the responsibility of having to press a microphone button before each transmission.

It is important to differentiate between voice-activated and sound-activated. VOX is the latter, meaning it is not just the sound of your voice which will activate VOX, but the sound of anyone’s voice or any other agent in the background that might make enough noise for VOX to pick up. In a noisy environment, then, VOX will be in constant “transmit” mode.

Adjusting VOX Settings for Your Environment

Some two-way radios with VOX do have sensitivity settings so that if VOX is used in an office or a setting where there tends to be excessive background noise, setting VOX to have lower sensitivity will prevent it from picking up on every sound in the background. The lowest sensitivity setting on VOX is best for noisy locations, while the highest sensitivity setting would be used in quieter environments. VOX circuitry also includes a delay feature, keeping the circuit from de-activating when the voice or sound stops. If there is a short pause during a conversation, then, this delay feature prevents VOX from automatically ceasing transmission during that brief pause.

1 comment April 8th, 2016