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.
You will read in the article
Non-traditional Palstar AT-Auto design
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, with the roller and rotary capacitor turning silent motors. In addition to this unusual solution, the designers incorporated several other interesting features into the AT-Auto...
Basic parameters
Control and measuring elements
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.
Napravo sa nachádza LCD display, manual tuning knob and AUTO/MANUAL and SELECT buttons. The rear display shows information about the condenser and roller settings, tuning status and instructions for the operator.
Tuning principle Palstar AT-Auto
Unlike other automatic tuners, where the tuner adapts the load to the transceiver in practically a few tenths of a second, AT-Auto will ask you to unlock it on the display after locking and measuring the frequency. Subsequently, the electronics will preset the roller and capacitor to the given band and ask you to re-lock, during which the tuner will be fine-tuned. These settings are stored in memory, speeding up future tuning. For example, retuning from 80 to 40m band takes 11 seconds, from 40 to 30m 4 seconds, from 30 to 20m only 3 seconds. Of course, retuning from 160 to 10m takes the longest, a full 45 seconds. Tento spôsob ladenia (zvlášť pri veľkom výkone) má výhodu v tom, že sa neopaľujú kontakty relátiek prepínaním pod výkonom a tiež minimálne zberacie kontakty kondenzátora a rolera.
Link to ICOM devices
Tento proces sa dá však obísť by connecting the tuner to the device via CAT. Súčasťou dodávky je aj prepojovací kábel ku zariadením ICOM. Prostredníctvom tohto prepojenia je informácia o frekvencii prenášaná do tuneru a elektronika aj bez zavysielania kontinuálne dolaďuje prispôsobovacie prvky. Kto dáva prednosť manuálnemu ladeniu, môže riadiacu elektroniku vypojiť stlačením tlačidla AUTO/MANUAL. Gombík manuálneho ladenia je len jeden, jeho zatlačením sa prepína ovládanie rolera a kondenzátora.
The SELECT button is used to select an antenna, symmetrical (via built-in balun 4:1) alebo asymetrickej. Ušetríte tak jeden prepínač dvoch antén.
Palstar AT-Auto practical test
Palstar AT-Auto showed several weaknesses in the practical test - it could not adapt to low impedance (below 12.5 ohm) in higher bands. In this case, the transformation properties of the coaxial cable can be used when the antenna is not connected to the tuner with an impedance repeater, but with a suitably chosen length of the coaxial cable, which takes care of the impedance transformation. Likewise, on higher bands, the tuner required more power (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, software revision 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.