Contrary to what most people believe, the radio frequency spectrum is a naturally-occurring and finite resource. Radio waves are primarily used nowadays as a means of transmitting information from one place to another, all without using any other kind of media.
Among the most important characteristics of radio waves are their wavelengths, also known as their frequency. Their frequency determines what position they are in the radio spectrum and from there, you can also determine all the other properties like radio wave propagation and potential use.
Because radio waves can travel across seas and cross country borders, it also tends to cause interference with the radio waves used by the locals. This is the reason why, before people can operate ham radios, they need to be familiar with all the rules, procedures, frequency plans, and other important information, such as how to find two-way radiofrequency.
Furthermore, amateur radio operators need to have a license before they can start using their radio equipment. Because different radio frequencies have different properties, some general harmonized bands define the main purpose of the frequency and the technical parameters of the transmitters using it.
These rules are accepted on the international level and they provide the basic guidelines on frequency use. Furthermore, each of these allocations is refined and certain countries might have special rules on how to use certain frequencies that operators need. The so-called allocations are accepted on international levels and provide basic rules for frequency usage.
Each allocation is then further refined and countries may have special agreements on how to use specific frequencies. The two-way radio, on the other hand, has a wave that travels parallel to the ground, which is why the curvature of the earth poses a problem.
That said, the two points on the earth with a distance between them that can be counted as straight lines are considered as a useful range for use in two-way radio communication. The range between these two points can be anywhere between four and six miles depending on the height of the transmitters.
You do not need to pull a tape measure to get the approximate range. You can do so easily using a simple mathematical formula. If you want to know how to extend your area by a certain range, you just need to multiply the height of the antenna (in meters) by 3.56 and you will get the answer in kilometers.
The Two Key Points
Two-way radios are among the most definitive early forms of wireless communications. Although they have been around for decades, two-way radios are still the most reliable forms of wireless communication without networks. The two key points that distinguish two-way radios from other forms of wireless communication include:
Instant Communication – You just need to press on the PTT (push-to-talk) button and you can immediately speak into the device. After that, it will start transmitting your voice over the air – this is all thanks to the quick-setup technology integrated into these devices.
Group Communication – Two-way radios can facilitate conference communication quite efficiently. However, this is not the same as the kind of one-to-many forms of communication that you are used to. This means that you can speak up to a thousand users at the same time, although it can be quite troublesome to talk with a thousand people.
Types of Frequencies
Two-way radios use two types of standard frequencies. These two frequencies are Very High Frequency (VHF) and Ultra High Frequency (UHF). These frequencies are used in combination with each other in a two-way radio system. To understand these two frequencies better, here are brief explanations of each of them:
UHF – It has a high frequency but its wavelength is short. This is why it can transmit more energy. For instance, the UHF applied in standard radio can vary from 400 to 512MHz but the wavelength is only between one and five feet.
This frequency is great for communications within a building that is made mostly of steel, such as most skyscrapers. However, because of its short wavelength, the signal cannot pass through many different obstacles.
When you are thinking of using your radio for indoor and outdoor coverage, UHF is the default frequency that most people use. UHF is also very versatile, which makes it the most common frequency band currently being used today.
The UHF bandwidth is the best choice for indoor use or in environments where there are lots of obstructions. This is the reason why it is used most of the time for city two-way radio systems. Some of its common uses include warehousing, hotel inter-communications, and in manufacturing plants and lots of other places.
UHF is so versatile that it is applicable in case you need enough coverage for both indoor and outdoor uses. The UHF band is so popular that more than 80% of business radio stations these days are all using UHF exclusively.
VHF – This has a shorter frequency but with a much greater wavelength. The common frequencies used for VHF are between 130 and 174 MHz only. However, their allowable wavelength exceeds 20 feet. This means that the energy used for transmission is lower but the signal can penetrate through most obstacles.
Furthermore, with VHF, the curvature of the earth does not have quite as much interference with the transmission. The downside is that the energy transmission is low because of the shorter frequency.
The VHF frequency band is more suitable for outdoor applications where you need a maximum signal to travel distance without any obstructions around. This is the band that is usually used for rural locations where there are not that many obstructions.
This is the bandwidth that most rural fire departments, long-haul truck drivers, and agricultural field operations use. It is usually the best choice anywhere there is plenty of open space.
900 MHz Onsite
If you need something more powerful for indoor use, you can choose to use the 900 MHz Onsite bandwidth. This bandwidth was uniquely developed for the Motorola DTR 650. Onsite radios do not require the users to have a license. Also, it is so quick and simple to set up and use immediately.
The typical industries that use this bandwidth include public primary and high schools, large retail institutions, hotels, and some light manufacturing facilities. All of these bandwidths are viable.
However, if you are looking for something very specific, you can just adjust the frequency bandwidths to your liking. Also, if you find yourself in a very rural area, you can tweak it so that you can get the most power.
Some Effective Tips on How to Adjust the Wavelengths Perfectly
When you are using a two-way radio, you might find that two waves are being used. The reason for this is because using just one of the waves will make your radio uses very limited. That’s because UHF can provide a shorter communication that is more reliable while VHF is better for long communications and it can pass through obstacles.
You can set which one of these radio waves is more dominant and that you can do by tweaking a couple of knobs to your preferences and specific needs. You can set your radio to prefer UHF over VHF, or vice-versa when you find yourself in rural areas where there are lots of open areas.
Adjustment of UHF
You need to tweak your UHF settings in a place that is apart from your destination. This means that you need to do this before leave your house or wherever you are currently. To make the adjustments, you need to twist the UHF control button until the frequency reaches a level that is higher than the balanced scale.
You can figure out the reading of the UHF right from the pointer. The VHF reading will automatically go down from the balanced state so you do not have to tweak it if you do not need to.
Adjustment of VHF
If you want a longer communication range, you need to adjust the VHF settings. The procedure is almost identical to how you adjust the UHF settings. You need to find the dial for the VHF and then twist it until you get an optimum frequency of 130 to 174 MHz. This will allow you to perfectly tweak the settings of the frequency.
When the frequency falls, the wavelength of the VHF will go up automatically. The UHF will also balance itself out.
The first thing that you need to do when you first get a brand new two-way radio is to find out how to find two-way radio frequency and adjust it. Setting up the frequency on the radio is quite simple. It is nothing more than adjusting the UHF and VHF settings to compensate for the curvature of the earth.
This will allow you to send clearer signals for far greater distances. Although your signal can’t avoid all obstacles, you must still avoid as many of them as you can. Also, your line of sight to the signal tower should be horizontally straight and a clear line of sight.
Richard Pennington is the one to consult when you need professional insight into electronics. With over a decade of experience in the field of electronics and communication engineering, he now serves as our chief content editor.
He is an advisor for multiple articles and videos with topics revolving around ham radios, electronics devices, and communication.