Many people who have never picked up a police scanner are completely unaware of all the messages that are flying past them at any given time. They are completely oblivious to the fact that, even as they busy themselves with other things, signals being sent to outer space, or discussing breaking news may be passing over their heads at the speed of light!
Tinkerers and hobbyists who enjoy experimenting with two-way radio have a better idea of this. And it’s something that anyone can learn!
In order to make things just a little bit simpler, several categories, terms, and explanations have been put in place. In this post, we’ll examine the topic of UHF and VHF. What does this mean? And how can it help you to find the signals you’re interested in on your digital police scanners?
UHF and VHF Explained
To put it simply: UHF stands for ‘Ultra High Frequency’, while VHF stands for ‘Very High Frequency’.
A UHF signal then is anything that falls between 300MHz to 3000MHz, whereas VHF is a little lower at 30MHz to 300MHz.
The full spectrum of radio waves goes from 30Hz all the way up to 300GHz, so this is still just a small fraction of the entire spectrum.
You will find a range of different bands and channels within both of these ranges, but there are a number of specific uses for each.
For instance, Marine VHF Radio falls right within the VHF bands – just as the name would suggest. This is the frequency at which marine vessels, harbours, and personnel communicate.
Likewise, in the UK – for example – businesses will use frequencies that range from 136 to 174MHz.
At the UHF end of the spectrum, you have the PMR446 license-free frequencies, which are reserved for those people who want to broadcast to a large audience free of charge. For broadcasting on other frequencies, you are supposed to first obtain a license in order to prevent jamming and interference.
Finally, the American FRS and GMRS radio frequencies are also found at the upper end – these being used for commercial walkie-talkies and other similar products.
How it Works
You may be wondering what all of this means in real terms. How do handheld two-way radio units pick up these different frequencies?
Essentially, any radio signal is an interruption to the electromagnetic field that can be found all over the planet – and even in space!
Waves occur via oscillations affecting electrons, and these waves can range in frequency. Very high frequencies are those which oscillate very quickly, while very low frequencies are those that are slow.
The channel that you listen to, is going to be dictated by which frequency you hone in on. So you might only listen to frequencies of a certain speed – and the band pass filter in your walkie talkie will ignore all other channels.
Of course if we go too high, that is when we run into trouble: microwaves excite the electrons so much that they can cook meat! Hence we find channels at the safe upper-end of this spectrum, which are referred to as UHF and VHF.