Palstar AT-Auto tuner
Quite demanding requirements are placed on the antenna tuner - the ability to transform the impedance from the nominal (50 ohm) to another in a wide range of frequencies and load impedances. In addition, we require minimal losses, reliability and easy operation. Palstar manual tuners for higher performances have gained popularity especially in the USA.
Most automatic antenna tuners use a system of switchable capacity and inductance by relays. However, the first automatic antenna tuner Palstar AT-Auto is based on the concept of a manual tuner, while the roller and rotary capacitor are turned by silent motors. In addition to this unusual solution, the designers incorporated several other interesting features into the AT-Auto….
Palstar AT-Auto is rated for 1500W power in the range 1, 8 to 30 MHz. According to the manufacturer, it can adjust the impedance 1200 +/- j1200 ohm in range 1,8 to 18 MHz a 1000 +/- j1000 ohm in the upper KV segment. However, while small boxes are on the market 14 x 32 x 40cm, weight 12 kg.
The front panel is dominated by a classic analog two-hand measuring device, which is used to measure forward and reflected power (the ratio is 3000/600W or 300/60W). It also has a PEAK HOLD function, which allows the measured values to be held for two seconds. The backlight of the meter can be turned on and off with the LAMP button.
On the right is the LCD display, manual tuning knob and AUTO/MANUAL and SELECT buttons. On the rear display, they show information about the capacitor and roller settings, tuning status and instructions for the operator.
Unlike other auto tuners, where practically in a few tenths of a second the tuner adapts the load to the transceiver, After locking and measuring the frequency, AT-Auto will ask you to unlock on the display. Subsequently, the electronics will preset the roller and capacitor to the given band and ask you to re-key, during which the tuner fine-tunes. These settings are stored in memory, thereby speeding up future attunement. For example, retuning from 80 it will work on the 40m band 11 seconds, like this 40 for 30 m 4 seconds, With 30 which is 20m different 3 seconds. Of course, it takes the longest to retune from 160 at 10m, and all of them 45 seconds. This tuning method (especially at high performance) has an advantage in that, that the contacts of the relays are not burnt by switching under power and also the collector contacts of the capacitor and roller are minimal.
However, this process can be bypassed by connecting the tuner to the device via CAT. The delivery also includes a connecting cable to ICOM devices. Through this connection, information about the frequency is transmitted to the tuner, and the electronics continuously fine-tunes the adjustment elements even without transmission.. Who prefers manual tuning, can turn off the control electronics by pressing the AUTO/MANUAL button. There is only one manual tuning knob, pressing it toggles the control of the roller and the condenser.
The SELECT button is used to select the antenna, symmetrical (through the built-in balun 4:1) or asymmetrical. This saves you one switch for two antennas.
Palstar AT-Auto showed several weaknesses in the practical test - it could not adapt to low impedance (pod 12,5 ohm) on higher bands. In this case, the transformation properties of the coaxial cable can be used, when we do not connect the antenna to the tuner with an impedance repeater, but a suitably chosen length of coaxial cable, which takes care of the impedance transformation. Likewise, the tuner demanded more power on the higher bands (over 10W) to measure the frequency. Due to the size of the tuner, this may not be a serious problem.
Despite the wide range of options, AT-Auto is quite simple to operate. In the next series, the manufacturer promises to add a BYPASS button, revision of software and other connecting cables to devices of other brands. Anyone can download the current version of the software from www.palstar.com and upload it to the tuner via the supplied 9-pin cable. The price is AT-Auto is just under 1200USD.