Hi Pat (Patrick? Patricia? The Puppet Formerly Known as ‘Postman’? – Just kidding!),
Happy New Year!
Now, to answer your question, two-way radios use a range of what are called ‘frequency bands’ – these are areas of the electromagnetic spectrum (a fancy name for the total range of electromagnetic radiation) that are used for audio communication.
Most radios will operate on either VHF (Very High Frequency – any frequency range between 30MHz and 300MHz) or UHF (Ultra High Frequency – any radio frequency range between 300MHz and 3GHz) modes, but the two types of radio are incompatible with each other, so a careful choice is required on the part of the user.
Generally speaking, UHF radios are better suited to urban or indoor environments, whilst VHF has a slight advantage if you’re using your radio outside. For more on the VHF vs. UHF debate, check out Wendy from Stoke-On-Trent’s question, posted in December.
Anyway, the lowest frequency is the VHF Lowband frequency (25Mhz – 50MHz), whilst the VHF Highband frequency is anything between 126MHz – 174MHz. The general UHF Band is anything between 403MHz and 512MHz.
Of course, the right frequency for you depends greatly on your needs. Is your radio system used professionally or as a hobby? Is security an issue or not really? That sort of thing.
Remember also that it is illegal to use certain frequencies, as they are used by the Emergency Services. Two-way radio use is actually quite tightly monitored/restricted, largely for public safety purposes.
According to a Motorola online course “Because frequency spectrum is an infinite resource, and the number of users in many areas is high, many radio channels are becoming crowded. Channel loading is a term used to describe the number of users assigned to the same frequency. Channel loading is so heavy in some areas that additional users are no longer allowed on particular channels, or frequencies. The use of channels is authorized and licensed by government agencies in most countries”.
The course goes on to say that,
“In all cases, a license to operate radio equipment is required and must be applied for with the appropriate governing body. The license is granted to operate on a particular frequency, or set of frequencies, with specific eligibility rules that must be met”.
Anyway, is pays to do a little research before heading out into the field with your walkie talkie.