Saturday, April 16, 2011

Would an antenna tuner improve the match and make the antenna work better?

Q Ray, K4YDI, asks, “I have just put up a used vertical antenna. I’m not getting the SWR I want (1.5:1 or less). Would an antenna tuner improve the match and make the antenna work better?”

A Unfortunately, you did not mention what SWR you are
seeing now. An antenna tuner may bring your SWR down
to 1:1, but if your SWR is already under 2:1, it is not necessary.

Remember that an antenna tuner doesn’t tune the antenna it only matches the impedance shown at the station end of the coax to that of the transceiver. Your transceiver is probably capable of delivering its full output at the 2:1 SWR, so a sufficient portion of your RF output is already reaching the antenna.

Whether your antenna radiates most of that power depends on the physical characteristics of the antenna and its associated ground system, not the impedance seen by the transmitter. 

To improve the radiation of a vertical, make sure you have
a good ground/radial system. Don’t rely on a single ground
rod driven into the soil. Try stringing out as many radial wires
as you can by just laying the wires directly on the ground the more the better and connecting them together at your antenna’s ground point. Your SWR may not be reduced (it may even rise), but I’m willing to bet that your antenna will “play” better. If you find this to be the case, then you can worry about burying the wires to keep them out of harm’s way.

From QST March 2001