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Several users of the AR-300 rotator have found that there is sometimes a difference between the indication and the real azimuth. This is probably causing the gears in the control unit to slip. This one rotátor je však dostatočne masívny a tiež niekoľkonásobne lacnejší ako iné rotátory. S jedným takýmto rotátorom som mal rovnaké problémy a tak som sa podujal vyriešiť vlastné zobrazenie azimutu – natočenia antény.
Idea je vlastne veľmi jednoduchá – the rotation of the tube from the rotator is transferred via cable transmission to the axis of the potentiometer, which is connected to the branch of the bridge. Voltmeter connected to the bridge is calibrated in degrees 0 to 360.
Let's start by making the sensor. For domestic use, where the rotator is under the roof, an uncovered construction with cable transmission is used. The potentiometer has 100 ohms (other values can be used), lineárnu dráhu. Vybraný bol kvalitný potenciometer – aripot. Prevod je zrejmý z fotografií. Vhodné je, aby 360° otočenia antény predstavovalo približne 2/3 otočenia potenciometra. Minimalizuje sa tým nepresnosť v linearite odporovej dráhy.
For outdoor or for portable use, the transmission and potentiometer must be built into the rotator chassis, which is more difficult. I recommend grinding a piece of welded wire on the gear in the rotator - this way we get the ability to turn more than 360 degrees and avoid the gear jamming.
Connecting the bridge is simple. To elaborate, I used the Electronic WorkBench program, from which the original schematic is - with a 5V power supply and a 3.6mV output. The sensor is R4. Other trimmers are multi-turn types. With such trimmers it is easier to adjust the range of the bridge, but ordinary trimmers can also be used. Resistors in the middle of the bridge served to reduce the range of the output voltage. The supply cable at the entrance to the cabinet is wound into a choke on ferrite material (3 turns on snap-on ferrite). The bridge has its own power source with a stabilizer that powers the meter bridge.
The greatest freedom is in the way of display. Very handsome kruhový zobrazovač je popísaný na webe OK2KKW. Je však troška zložitejší na výrobu. Keďže meriame napätie, môžeme použiť klasické ručičkové meradlo, ociachované v stupňoch. Ďalšia možnosť je voltmeter s LED, pričom nastavíme výstup z mostíka tak, aby 360° predstavovalo 36mV (360mV alebo 3,6V podľa rozsahu voltmetra). Pôvodne som túto verziu plánoval, ale v miestnych obchodoch s elektrosúčiastkami nemali toto stavebnicu LED voltmetra. Použil som preto hotový modul LCD voltmetra za 145Sk. Ďalšou možnosťou je zobrazovanie azimutu na počítači, napr. jednoduchým meračom cez COM port.
I mechanically blocked the azimuth display in the rotator control unit. It is no longer necessary and by blocking it we get the possibility of turning more than 360° and avoid difficulties with a dead spot. Ten sa totiž pri rozbalansovaní presunie zo severu inde, čo môže byť nepríjemné. Urobíme to vyosením prevodu viditeľného zo spodnej strany ovládacej jednotky napríklad kúskom dreva.
Calibration requires a little patience. Vhodné je vyrobiť si „nulový“ a „tristošesdesiatstupňový“ rezistor. Nebude potrebné tak anténu v priebehu kalibrácie stále otáčať. Anténu nastavíme na 0° a ohmetrom zistíme odpor potencimetra. Túto hodnotu odporu potom realizujeme rezistorom (alebo zložením viacerých rezistorov). Rovnako si pripravíme druhý rezistor pre uhol 360°.
We replace the potentiometer with a "zero" resistor and balance the bridge - there will be zero on the scale. Now we connect the "three hundred and sixty degree" resistor and use the upper trimmer to set the full deflection on the meter (with a hand meter) or 36.0 on the digital meter display. The elements interact with each other and therefore we repeat the entire procedure until the balance and 360° display are flawless. Po skalibrovaní trimre zakvapneme farbou.
One of the possible versions of the antenna rotation indicator - displaying the azimuth can be seen in the photos. With a digital display with a resolution of one degree, the last digit may jump by a degree or two due to wind.
I have been using the AR-300 rotator for several years and I am satisfied with it despite its shortcomings. It can also handle a smaller KV turn signal provided the upper bearing is used. Asi dva roky otáčal ľahkou 3-elementovou smerovkou na 28MHz a teraz otáča 2-elementovým tribanderom, pričom s oboma anténami bez ujmy prežil niekoľko silných vetrov.