Antenna Tuning Units, ATUs or Antenna Tuners are an essential item of equipment for any HF amateur radio or short wave listening station. These antenna tuners enable the antenna to be matched to the transmitter or receiver.
For transmitting stations, ATUs are of particular importance because modern semiconductor based transmitters need to see a load that has a low level of reflected power to operate efficiently. The ATU / antenna tuner enables this to happen. Buying the right antenna tuner or ATU can enable the overall station to perform with greater efficiency.
When selecting an antenna tuner / antenna tuning unit, ATU to buy there are several points that may be of interest:
- Frequency coverage: Antenna tuning units / antenna tuners are typically intended for HF band operation, but just check that t covers the bands that are required.
- Power capability: There are many different ATUs / antenna tuners available. The power rating is an important parameter, especially if high power operation is envisaged. High power ones will work equally well with low powers, but it is important to ensure that the power rating is not exceeded. Switches, coils, etc may overheat or arcing may occur if the power rating is exceeded. As some ATUs are intended for low power, QRP operation, these should not be used for power levels over a few watts.
- Manual or Auto: In the early days of amateur radio, all ATUs were manual and often boosted late control knobs onto e front panel for easy and accurate adjustment of the variable capacitors - often a large switch was also used as this matched the capacitor knobs and also the switches tended to be large to withstand the power. Today many ATUs can link to the transceiver and automatically tune themselves to provide the best match at the press of a button.
- Check that your transceiver is supported: When buying an automatic ATU / antenna tuner, check that your particular transceiver is supported. Most of the later ones from he main manufacturers, Kenwood, Icon, and Yaesu will be, but check. Also different options are required for the different manufacturer. This is typically a different interconnecting control lead, and there may be a link to be changed inside.
- Impedance match range: Despite some of the hype, not every ATU can math every antenna. They have an impedance range over which they can match. Check what this is and opt for the best one. It is normally not possible to know exactly what impedance range any antenna will present under all conditions, but make an educated guess. Select the one that gives the best range, etc.
- Balanced or unbalanced: Coaxial cable is an unbalanced feeder, and often ATUs / antenna tuners will match from unbalanced to unbalanced. If you are using a balanced antenna that uses twin / balanced feeder then you will need an ATU that supports this, or you can use an additional balun.
There are many different antenna tuners / ATUs that are available to buy for amateur radio and other applications. There is a good selection so it will be possible to choose one that fits the requirements well.