StillwaterEMT42

Quoted from outside resources -

"
Tuning is the process of adjusting an antenna so that the radio's output power is turned into radio signals as efficiently as possible. In more tangible terms, it involves incrementally increasing or decreasing the length of the antenna. The goal of antenna tuning is to match the antenna's physical length with that of the radio frequency being used, so as to ensure optimal performance and transmission efficiency.


An antenna's efficiency is measured by the Standing Wave Ratio, or SWR, which represents how much of the radio's power is being turned into radio signals by the antenna. An SWR reading of 1.0 indicates that 100 percent of the radio's power is being transmitted, while a ratio of 3.0 means that only a third of the power is being transmitted by the antenna.


The goal of antenna tuning is to achieve as low an SWR reading as possible. While low SWR readings result in the best performance, high SWR readings have more worrying implications than poor transmission range. In fact, operating a radio at SWR levels above 3.0 can cause damage to the radio because all that excess output power is reflected back at the radio as heat, which can result in permanent damage to the unit."




That was for the theory, now for the guide!


You'll need to install everything correctly, make sure it works, and then go to RadioShack and pick up a SWR Meter and a coaxial jumper.

Jumper - http://www.radioshack.com/product/in...ductId=2102420


To start, you'll want your heep in an open area, free from trees, walls, hills and rocks. Anything for the signal to bounce around and mess up your readings. Be inside the vehicle, close the doors and windows.



-Disconnect your antenna from your radio, and plug the antenna into the plug marked "ANT, ANTENNA" on the SWR Meter. Take the jumper cable, plug one end in your radio, and the other into the "TX or RADIO" spot on the SWR meter. By doing this, you've put the meter in between the radio and the antenna.



-You'll be wanting to start the test on Channel 1, so set to Channel 1 and set the SWR meter to "FWD"
-Key up the microphone, and while your holding down the mic button, turn the meter dial labeled "Set" or "Adjust" until the meter reading reaches the position marked "Set."
-Keep holding the microphone button! Press the "REF or SWR" button on the meter and document the number it gives you. NOW you can stop keying up the mic.

-Repeat these steps on Channel 40. Write down that number as well. Once you get both numbers...


-If your reading on Channel 1 is greater than the reading on Channel 40, your antenna is too short and you need to lengthen it. Most steel whips have a place to adjust the length, as well as most fiberglass antennas have a screw in the top to adjust.



-If your channel 1 reading is LESS than channel 40, your antenna is too long and you need to shorten it. You can make the same adjustments as before, but if your antenna doesnt have an adjust, yes, you'll need to cut it. Cut in very short increments between testing.. nothing is worse than cutting off too big a chunk, and having your reading go too far in the other direction.





By tuning, you want to establish the lowest SWR reading you can possibly acheive, though this number cannot go above 2.0 . You want your readings on Channel 1/40 to be as close as possible, if not the same.





When your readings are all set, disconnect the meter and reconnect your antenna back to your radio. Have fun with your new tuned antenna! You will notice very large differences in quality when your out on the trail.








Sources :



Myself,
www.roadtripamerica.com