Classic antenna rotation indicator

Several users of the AR-300 rotator found out, that sometimes there is a difference between the indication and the real azium. This is likely to cause the gears to slip in the control unit. This however, the rotator is sufficiently massive and also several times cheaper than other rotators. I had the same problems with one such rotator, so I set out to solve my own display of azimuth - antenna rotation.

The idea is actually very simple - the rotation of the tube from the rotator is performed on the axis of the potentiometer via a cable transmission, which is involved in the branch of the bridge. Voltmeter connected to the bridge is measured in degrees 0 to 360.
We will start the production of the sensor. For home use, where the rotator is under the roof, an uncovered construction with a cable transmission is used. It has a potentiometer 100 ohms (other values ​​can be used), linear path. A quality potentiometer - aripot - was selected. The transfer is evident from the photos. It is suitable, that the 360 ​​° rotation of the antenna represents approximately 2/3 potentiometer rotation. This minimizes inaccuracy in the linearity of the resistance path.

Snímač natočenia

For outdoor, resp. For portable use, the gear and potentiometer must be built into the rotator chassis, which is more challenging. I recommend grinding a piece of welded wire on a gear in a rotator - we will achieve the possibility of turning by more than 360 degrees and avoid jamming the transmission.

Connecting the bridge is easy. I used the Electronic WorkBench program for debugging, of which is the original scheme - with 5V power supply and 3.6mV output. The sensor is R4. Other trimmers are multi-turn types. With such trimmers, the range of the bridge is easier to adjust, but it is also possible to use conventional trimmers. The resistors in the middle of the bridge were used to reduce the range of the output voltage. The supply cable at the entrance to the cabinet is wound into a choke on a ferrite material (3 threads on snap ferrite). The bridge has its own source with a stabilizer, which powers the bridge gauge.

Schéma zapojenia klasického indikátora azimutu

Snímač natočenia na plošnom spoji

The greatest freedom is in the way it is displayed. Very nice the circular display is described on the web OK2KKW. However, it is a bit more complicated to produce. Because we measure voltage, we can use classic hand gauge, calibrated in degrees. Another option is voltmeter s LED, while setting the output from the bridge so, so that 360 ° represents 36mV (360mV or 3.6V depending on the voltmeter range). I originally planned this version, but in local electrical stores they didn't have this LED voltmeter kit. I therefore used the finished one LCD voltmeter module for 145Sk. Another option is azimuth display on computer, e.g.. simple meter via COM port.

I mechanically disabled the display of azium in the rotator control unit. It is no longer necessary and by disabling it, we get the possibility of turning by more than 360 ° and prevent problems with a dead point. This is because it moves from the north elsewhere during balancing, which can be annoying. We do this by offsetting the gear visible from the bottom of the control unit, for example with a piece of wood.

Calibration requires a little patience. It is advisable to make a "zero" and "three hundred and sixty degree" resistor. It will not be necessary to constantly rotate the antenna during calibration. Set the antenna to 0 ° and use an ohmmeter to determine the resistance of the potentimeter. This value of resistance is then realized by a resistor (or by assembling multiple resistors). We will also prepare a second resistor for a 360 ° angle.

We will replace the potentiometer with a "zero" resistor and balance the bridge - there will be zero on the scale. Now we connect a "three hundred and sixty degree" resistor and set the full trimmer on the scale with a full deflection (at the hand scale) or 36,0 on the digital gauge display. The elements interact with each other and therefore we repeat the whole procedure until the balance and the 360 ​​° display are error-free. After scalibrating the trimmer, drip paint.

Detail meradla na 99 stupňoch

One of the possible embodiments of the antenna rotation indicator - azimuth display is evident from the photographs. In digital display with a resolution of one degree, the last digit can skip a degree or two due to the wind.

I have been using the AR-300 rotator for several years and I am satisfied with it despite the lack. It can also handle a smaller HF indicator, provided the top bearing is used. He has been rotating a lightweight 3-element turn signal at 28MHz for about two years and now he is rotating a 2-element tribander, with both antennas he survived several strong winds without damage.

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