The honest answer is unfortunately, there is no a simple answer. Just like when listening to a car radio, which I'm sure you have all done and all noticed reception or range changes due to many factors. How many times have you come accross a radio station that you like but only get sometimes. The two way radio signal deals with similar issues. Many things effect the range of the two way radio, such as type of antenna, antenna gain, the frequency, power output, and obstacles and terrain.
Since this is going to be a short article I'll only breifly discuss them.
First, let's discuss frequency. Although today there are many frequencies such as, but not limited to, 700 mHz, 800 mHz, 900 mHz, UHF and VHf. The largest majority of two way radios are in the UHF & VHF frequencies. The main difference between UHF and VHF is the wavelength. UHF has a shorter wavelength which makes it better for more dense terrain. When I say more dense terrain you could be dealing with more hills, more trees, or more buildings. UHF has better penetrating capabilites. UHF will deal better with going thru walls or other obsticals then VHF.
VHF has a longer wavelength which means that it will transmit futher for the same amount of wattage vs UHF. VHF will not penetrate, ie. go thru walls or other obstacles, as well as UHF. VHF performs better for distance(i.e. goes further when you have a clear line of site), but UHF has better penetrating power (i.e. goes thru walls or orbstacles.)
Secondly, let's discuss the antenna. I know there are many types of antennas but for our dicussion let's say they are both the same except one is longer than the other. For our discussion though we are going talk about pans. Why pan's you say? Well I like to keep things simple. Let's say we put two pans that each hold 1 gallon out in the rain. One pan is 6 inches round and the other is 12 inches. Which will fill faster? Well although the 12" inch will be shorter it will fill faster since it covers more area for the rain to fall into. So simply put when dealing with two of the same types of antennas the larger should perform better.
Lastly, let's discuss what all guys like, which is the power out. Power output on two way radios is given in Watts. Typically portable or handheld business two way radios come in the 4-5 watt power output and will have an effect range of approximately 5-7 miles depending in part on some of the conditions we have discussed. When discussing mobile radios they typically start around 15-20 watts and have an effective range of 12-18 miles. For increased range there are repeaters, mobile repeaters, trunking equipment and many other things.
I hope this little article has helped but if you need any other help related to two way radios please feel free to contact one of knowledge, friendly and helpfull staff at www.moradio.com. Thank you.
"First Published on Qassia" by Patrick Strutman