Mobile two way radios are built to install and operate in automobiles, pickups, commercial trucks, off-road or recreational vehicles and, for some models, even motorcycles. The power, advanced features and versatility of the typical mobile radio allows it to be easily converted into a base station. It can be placed on a table or desk without a mount or hardware, connected to a proper antenna, powered on, and it's ready to go on the air.
Of course, there is a little matter of power. A mobile radio is specifically designed to operate on DC power from a vehicle. It has no internal power transformer or inverter of its own, so it isn't made to plug into the AC wall outlet of a home or office building. In that case, how do you power a mobile radio for use as a base station? That's easy. Get a power supply.
So, how do you choose the right power supply for your radio?
First, you will need to determine how much power your radio requires. A radio that is always on, but only listening, will use a minimum of power while idling in receive mode. However, the moment the Push-To-Talk (PTT) is pressed, the power needed to transmit will spike considerably. How much? That depends on several factors, not the least of which is the transmit power level set or programmed into the radio for a particular band or frequency.
Second, you will need to consider how the power supply will be used. Will it power only one radio, or multiple transceivers at once? Will the radio sit next to or on top of the power supply, or will it be set somewhere else on the desk or bench a short distance away?
Last but certainly not least, you will need to figure out what type of power supply will work best within your budget.
Where do we begin? For starters, let's discuss how much power you will need for safe and stable operation. For this, you will need the operating specs of your radio. Since mobile radios are designed for use in a vehicle, they will typically need Direct Current (DC) between 12VDC and 13.8VDC operate. The wattage is also important, as it will fluctuate greatly depending on what state of operation the radio is in, i.e. whether it's receiving or transmitting a signal. This means the number of Amps it pulls while in each state of operation will also vary greatly.
And yes, there is a formula to calculate how much power you will need for your particular radio.
E= Voltage or Volts (V)
I= Current or Amps (A)
P= Power or Watts (W)
For example, let's calculate the amp draw of a 15W mobile radio on 12 volts. 15W / 12V = 1.25A. Simple, right? Well, not exactly. There are other variables to consider. For instance, there is an initial power surge or spike when the radio is first turned on, and again each time the PTT button is pressed to transmit. That surge will vary each time, and the power supply will need to be able to handle those momentary spikes in power draw.
There is variance in how many peak amps a radio will consume, and there is variance in how many actual continuous amps a power supply can handle. Plus, you have to factor in the heat produced and average load a power supply is under. Considering all these variables, there is not an exact formula for figuring this out. A better, safer amp rating to use is the maximum current consumption or amp draw listed in the manufacturer's specifications or in the owner's manual for the radio.
To the average layperson, all this sounds overly complicated. So to simplify the process, here are some general guidelines for choosing the right size power supply for your radio.
If you have a CB radio, which is limited to a maximum of 4 watts. As long as you aren't pumping out more than the legal limit through your antenna, your amperage requirements should be rather low. A 20 amp power supply should be more than enough needed to power a CB radio as a base station, with power to spare.