The first thing you need to do is find a suitable location to park your vehicle. There should be no obstructions, such as trees or buildings, within 10 to 15 meters of your antenna. Neither you nor your buddies should be hanging out around the car, either. Make sure that you’re inside with the doors and windows closed to ensure an accurate reading.
The next step is to hook up the SWR meter. First, disconnect the coaxial cable from the back of the radio. Reconnect this end of the cable, which is going to the antenna, to the SWR meter in the connector marked “antenna” or “ANT.” Next, use the jumper lead to connect your radio and the SWR meter through the connection marked “transmitter” or “XMIT.”
Now you are ready to measure the SWR on a few different channels. Remember, throughout this process it's important to keep the microphone the same distance from the meter for each test.
Set the switch on the SWR meter to “FWD.”
Turn the radio to channel 1.
Key the microphone (depress the button and hold it).
Turn the knob on the SWR meter labeled “SET” or “ADJUST” until the needle reaches the setting position at the end of its range.
While still keying the microphone, flip the switch on the SWR meter to the “REF” or “SWR” position.
Quickly record the reading given by your SWR meter and release the transmit key on your microphone.
You are now going to repeat this process for channel 40. Follow steps 4 through 9.
The objective behind tuning your antenna is to make these two readings as close as possible. Getting down to a 1.5:1 ratio or below makes for a passable broadcast signal. There are two basic points to understand before adjusting the length of your antenna:
If the SWR on channel 40 is higher than that on channel 1, your antenna is too long.
If the SWR on channel 1 is higher than that on channel 40, your antenna is too short.
