Radio Tuner Antenna

The phrase radio tuner antenna is a bit of a misnomer as an antenna does not tune the radio or any part of it.  What an antenna tuner does is transform the impedance at the antenna feed output at the radio to a value that your transceiver can handle, normally 50 Ohms.

A tuner acts as an adjustable impedance transformer between the radio and the antenna. It takes whatever impedance the antenna system presents, up to the design limits of the tuner, and attempts to convert it back to 50 Ohms--or something reasonably close to that value for the transceiver. When the transceiver "sees" a 50 Ohm impedance, it is able to load or produce it's maximum designed RF output into the system because it is designed to operate into a 50 ohm load.  Power is transferred through the antenna tuner, to the feed line and, ultimately, to the antenna, absent any losses incurred along the way.  If you have high losses, you will not be able to get a good signal.

These losses are the reason that the highest efficiency feed-line for each individual case is desirable and why some amateurs use ladder line on HF, which has the least loss per foot, which means maximum power at the input terminals of the antenna.

Most antenna tuners have an inductance rotary switch and two capacitors, often labeled ANTENNA and TRANSMITTER. In some antenna tuners, the inductance switch is replaced with a continuously variable inductance, popularly known as a roller inductor.  A tuner with an inductance switch is the most common.  Place both capacitor controls at their mid-range positions. Don't trust the knob markers if this is your first experience with the tuner!  If you are comfortable with the next procedure, remove the cover of the tuner and turn the knobs until the moving capacitor plates are only half meshed with the stationary plates. If the knobs are pointing to half scale with the reference markings on the knobs and front cover, consider yourself lucky. If not, loosen their Allen screws and rotate the knobs so that they point to mid scale.  Re-tighten the knobs, replace the tuner cover and you're ready to go.

Turn the radio on and tune receiver to an unused frequency on the band you desire, listen for a few seconds, with the antenna and transmitter controls at mid scale, move the inductance switch to each of it's positions until you hear the loudest noise or signals coming into your radio. Then, rotate the antenna and transmitter controls until you get to the absolutely loudest noise or signal level on the radio. All three of these controls interact with each other so practice on several bands to get the "feel" of the procedure

Select your final band of operation and repeat the procedure above. When noise peaks out using your ears and the S meter, your tuner settings should be very close for final operation.  With your rig set to low power monitor the frequency to assure that it is not in use, send your ID then transmit a continuous carrier while you tweak the antenna and transmitter controls for the lowest reflected power reading with the highest output power as read on the Swr/Watt meter.

You may find that you have to vary the position of the inductance switch a position or two either way to get your best match.
Play it safe and un-key before turning the inductor switch...un-key first....turn the switch...key up....repeat as needed until lowest SWR and maximum output. Be gentle to your radio; keep the key-down periods as short as possible. Depending on the impedance at the antenna input (and the overall design of the tuner) you may not be able to obtain a flat 1:1 SWR on all frequencies and bands

Also important to remember is that your Swr will change, go up, as you tune further away from the frequency you used to "trick" your radio! So re-check and re-tune as needed as you move around the band.

You can get an idea of your SWR bandwidth by starting with your original frequency, and using the procedures above with low power, (don't move any knobs or switches after best setting)....sweep or tune your VFO up and down the band while watching the SWR readings and note the frequency where the SWR reaches 2:1 at the highest and lowest frequency. Stop there!