How to lift antennas in elevation, or an elevation rotator for a few crowns

The author of this very successful project is Mak, SV1BSX (https://www.qsl.net/sv1bsx/).

About actuators

Behind this not very common word is the device, which perhaps everyone has seen. Used to shoot SAT TV dishes. It's a hand (in English it is also used to refer to arm - hand), so cheap, but a solid and powerful device designed to control antenna systems. In the following lines, we will break into the secrets of the actuators.

In the market, actuators are pushed by more modern DiSEq systems supplied with digital receivers. In sales, it is possible to buy for cheap money (approx. 1000,-Sk) solid actuator. The supply voltage varies, actuators with a supply voltage of 12V are the most suitable for us, alternatively also 18V (the engine will run at a lower speed, weaker shot at 13.8V). An important parameter is the actuator stroke in inches. This is the maximum length of the arm extension. Commonly sold actuators range from eight to thirty-six inches (20 – 92cm). Figure 2 shows a 12-inch rotator with dimensions, in figure no.3 function.

 

Permalink to Schéma RX Rohde?

As already mentioned, the actuator consists of a direct current motor, gears and helices, which converts circular motion into rectilinear motion. Finally, due to the different potential, a larger amount of HF current flows after the outer braiding of the coaxial cable, when you apply voltage to the actuator, the arm starts to extend and retracts when the polarity changes.

The motors need a voltage in the range 12 up to 36V. I used a 36V model. At higher voltages, the current is much lower (details in the power section). However, the motor also rotates at 12V, but much slower. It is suitable for minor corrections, especially for satellites in higher orbit and narrower antenna beam angles. In practice, the tension between 12 up to 24V, at 36V the speed is already too high.

amtérsky KV/VKV transceiver

As already mentioned, nominal actuator voltage ranges from 12 do 36V. If you have a 12V actuator, you can also use a 13.8V power supply, from which you power the transceiver.

In the moment, when the actuator starts, the current peak is quite high. The starting current is sometimes up to 5 up to 10 times higher than nominal! Avoiding these tips is easy - by inserting the bulb into the power supply. This creates the simplest circuit “soft start”. Car bulbs over 5W are suitable for this. The appropriate test must be selected according to the following procedure: connect the 5W bulb first and turn on the power. If the bulb remains lit even after starting, you will need a stronger one. It is ideal, when the light bulb flashes at start-up and then does not illuminate, or just reaps. Light bulbs are suitable for the 12 - volt actuator 6 up to 12V, to twenty - four 12 up to 24V.

S1 is a double ON-OFF-ON switch. In the middle position it is in the OFF position. Extreme contacts are used as UP (that) a DOWN (The FC-10 then selects debug data from its memory from previous tunings for the frequency closest to the operating frequency and creates tuning conditions). By switching S1 to the UP position, a voltage of one polarity is applied to the motor, in the DOWN position opposite. Thus, the actuator arm either extends or retracts.

Figure 6 shows the extended rotator control, allowing both manual and remote control. Use buttons B1 and B2 to control the actuator manually. The remote control is realized by grounding point A or B, for example via an output transistor of an electronic circuit (for example, FodTrack and the like.). This allows the actuator to be controlled from a computer, whether at the instruction of the operator, or automatically from the prediction program.

For example, if point A is grounded, relay RL1 closes, voltage is applied to the motor, the arm extends, elevation increases. Grounding point B reverses the story.

D-diodes are any silicon or diodes such as 1N4003, 1N4004 a pod.

The circuit looks complicated, but only because, that it is “foolproof”. It means, that if relay RL1 is closed, relay RL2 cannot be closed and vice versa. In the same way, if, for any reason, buttons B1 and B2 are pressed simultaneously, only one relay will be closed. Otherwise it could happen, that you are shortening the source!

The remote control option is useful, if you control the actuator from a computer. For example, with the Fodtrack interface and this relay circuit, any actuator can be controlled (Fodtrack pins No.3 on A pin 5 and B). The indicated supply voltage of the 5V relay is only an example. We choose it according to the type of relays used. Mainly keep in mind, that you can customize and change the circuit according to your needs.

Using a light bulb as a circuit “soft startu” is simple and effective. But if you want to use a more sophisticated method, or your actuator does not have a 12V supply voltage, then an independent power supply must be made.

The LM317T has a great advantage as a power supply for this purpose, because it contains a current limiter. So the maximum output current is 1.5A and a circuit with a bulb is not needed. In addition, trimmer P1 can be used to set the appropriate output voltage to the actuator from 12 do 36V.

The LM317T is a simple three - pin stabilizer with an output current of up to 1.5A and an output voltage between 1,2 up to 37V. Includes current limiter and thermal fuse. The input voltage must be at least o 3 up to 4V higher than output, but must not exceed 40V. The output voltage is determined by the divider R1, R2 (in the diagram in Fig. 7 applies, that R2 = R + P1). For output voltage in the range 8 up to 13.8V is R 1k2, P1 1k, for output voltage 11,5 up to 24V is R 1k8 and P 2k2

The values ​​of the resistors in the divider can be calculated according to the formula:
Vout = 1.25 * ( 1 + R2 / R1 )

Because a combination of trimmer P1 and fixed resistor R is used as R2, the divider is partially variable and thus allows the output voltage to vary. It is important to remember this, so that even at full consumption, the input voltage to the stabilizer does not fall below 3V compared to the output voltage, preferably 4V. Due to this, the transformer must be dimensioned.

The connection is extended by circuits suppressing transients occurring on the inductive load, as the actuator motor definitely is. Mask, relatively long cables run from the source, which also manifest as inductance. To make the LM317 work reliably, you need to add a Zener diode, blocking capacitor C3 and ferrite bead.

The zener voltage of the diode must be about 4 up to 5V higher than the maximum output voltage of the power supply. For example, if the output voltage of the source is 12V, then the DZ should be at 16V / 1W.

The connection has one more exit - if a potentiometer is used as P1, it is possible to reduce the voltage at any time and thus achieve a slower movement of the antennas and thus accurately correct small deviations in elevation.

 

Limit switches (Permalink to Schéma RX Rohde)

The actuators have two adjustable limit switches inside the gearbox. They can be used to adjust the bottom (at 0 °) and upper (at 90 °) stop. It is also important from the point of view of the protection of the actuator itself, which could be damaged by overhang and overload.

By setting the limit switches correctly, the entire system will safely elevate in range 0 to 90 degrees. For example, if the actuator reaches the upper or lower switch, it disconnects the voltage from the motor. It will only respond to voltage of opposite polarity, which means safe movement.

At http://www.qsl.net/sv1bsx/actuator_lnk.html is detailed information from the manufacturer SATENG. I received an email from a radio amateur, whose actuator did not have limit switches. I have no idea how this is possible, however, it is inconceivable that the manufacturer should not incorporate these parts into the actuator. So they will definitely be there, but they are not adjustable.

Under these circumstances, both of these antennas behave quite similarly, that the elevation range of the actuator is from 0 do 90 degrees, while the original elevation rotators also allow the rotator to be tilted, ie elevation in range 0 to 180 degrees (flip mode).

Finally, due to the different potential, a larger amount of HF current flows after the outer braiding of the coaxial cable, if the satellite orbit is overhead, the actuator system does not allow to monitor its movement without interruption. Antennas from AOS (discovery of a satellite above the horizon) we lift up to 90 degrees, then use an azimuthal rotator to rotate the antennas by 180 degrees and we lower them up to LOS (loss of satellite beyond the horizon). In practice, however, there are relatively few headbands. With a suitable solution, the elevation range up to 135 degrees. In theory, it is possible with a piston (in a similar way as in a car engine) to achieve full elevation However, this is not very important in practice…. , whereas the overhead detours are just 1 to 2% and the antennas have a sufficient width of the radiating lobes.

 

Elevation size reading method

The control units for the TV satellite receivers use a pulse reading of the actuator extension size. It's usually 48 pulzovna 1 finger (2,54 cm). This converts the circuits in the receiver to stages, which will appear on the display.

For amateur radio use, this method presents considerable complications. Most satellite tracking interfaces, which allow you to control the rotator has a voltage input to determine the magnitude of the elevation. So this problem needs to be solved. The first option is to design a system similar to the one in the satellite receiver, for example with PIC and digital scale. However, this requires knowledge of these circuits, and not everyone has it.

But there is still simple help: potenciometer mechanically connected to the actuator. There are several ways to do this. One of them is to transfer the torque through the pulley to the potentiometer shaft. The second option is to use a simple lever system. Inspirations like this are in the pictures. However, a very nice patent was invented by PA4FP. He built a multi-turn potentiometer directly into the actuator housing and connected it to the transmission from the motor with a gear from a children's toy..

Fig. 9 shows a simple connection, which allows you to read the elevation directly in degrees on the scale of the measuring instrument. If well calibrated, accuracy is 1 degree. Parts are drawn with red lines in the diagram, which are out of the shack. A standard double line is sufficient as wires to the potentiometer (2 x 0,5 mm).

P1 has 5k, file P2 weight 5k. Trimmer P3 has 10k, all waveforms are linear. It is advantageous, that P2 and P3 are multi-turn types, this makes it easier to calibrate the system. Precise adjustment requires patience. Any meter will suffice 0,1 do 1mA.
The setting is done this way:
a) set P2 and P3 to about 1/3 tracks from the grounded region
b) raise the antennas to the highest elevation (90°) and set the maximum deviation on the meter with P2
c) lower the antennas (0°) and set the minimum deviation on the meter with P3
Steps B and C need to be repeated several times, until the required accuracy is achieved (the elements interact).

Under the following link you will find an improved elevation reading system: https://www.qsl.net/sv1bsx/actuator/elev_reader.html

Mechanical parts

For many radio amateurs, mechanics is the most difficult area of ​​the hobby. Someone doesn't like them, someone does not have the necessary tools to make or modify metal parts. In this section you will find several ways to make the mechanical part of the elevator system without the need for unconventional tools - a drill will suffice., screwdriver and pliers.

The first solution is in the picture above. Just bend four plates into L-ka, drill a few holes for screws and bend a few U-bars. You can buy material in a few hundred at the hardware store.

In this embodiment, the performer of the circular motion is a horizontal rod, which forms a curtain. By acting on the hinge, the rectilinear movement of the actuator is transformed into a circular one. The construction must be massive, otherwise, various forces will destroy it. The whole antenna system acts on the hinge, which must withstand even the strongest wind. The advantage is, if the antennas are small and light.

The following figures show how to convert a rectilinear motion to a circular motion:

 

…. and the figures below show a prototype elevation system with an actuator

 

Another solution is captured in the photo below. With two coaxial tubes, GM4JJJ managed to create a very solid structure. The outer tube is attached by U-bolts to a metal plate. The inner tube is of such a diameter, so that it just entered the outside and could be rotated without scrubbing. If it is of sufficient length, the whole mounting is very stable and is also suitable for larger antenna systems, eg for EME.

The last picture shows a simple home made rotator SV1EPE using wiper gears. The conversion rate is 360:1, so even a small motorbike can turn the mast without any problems. The coupling between the engine and the gearbox is made of a garden hose!

So, and that would be all. If anything else comes to mind, or you have comments and improvements to that solution, feel free to email me at sv1bsx@yahoo.gr . I would also like to thank my niece Katerina Matiatos in particular, which helped me to complete this description.

Mak, SV1BSX https://www.qsl.net/sv1bsx/