When is an Antenna Tuner not an Antenna Tuner?

31Mar16

When is an antenna tuner not an antenna tuner?

Answer: all the time!

“Antenna tuner” is really a bad name for the devices that present a low SWR to our transmitters and amplifiers. In the ’50s and ‘60s they were often, and more correctly, called “transmatches” for transmitter matchers.

Palstar BT1500A 1500 Watt Double L Balanced Antenna Tuners BT1500A

Palstar BT1500A 1500 Watt Double L Balanced Antenna Tuners BT1500A

When used in the shack, an antenna tuning unit (ATU) “looks” at the antenna, the feed line, the connectors or adapters and other factors to adjust the impedance and resistance values to an acceptable level for the transceiver. This process may be done manually by adjusting capacitors and inductors via front panel controls on the tuner, or automatically with microprocessors and relays switching inductors and capacitors without user intervention. Whatever method is used, the ATU doesn’t “tune” the antenna. It electrically matches the antenna SYSTEM to your transmitter.

To prevent feedline losses, a remote ATU mounted very near the antenna feed point can be a better way to go. This is especially true with ground mounted verticals, where access to service the ATU, if necessary, is easily accomplished. This approach will also limit common mode currents on the feedline, thereby reducing RFI and stray RF in the shack.

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