Interesting comparison of tracker designs

Just saw this:

Super interesting comparison among different tracker designs (Alt/Az,Alt/Az/Tilt, X/Y)

X/Y looks really promising for dish antennas. Any thoughts? We are heavily brainstorming for v3 !

I know a lot about XY. I own one!!

I will explain the benefits and drawbacks of such a design

Compared to the same size motor and gearbox XY is:

Faster when it really counts, when satellite is directly overhead and moving fastest compared to ground station.
Can move in any direction without doing “a flip” like normal azimuth elevation types

Both Motors are normally identical meaning you can just have one spare motor and gearbox to replace either X and Y as they are both the same.

As a result it normally ends up with a cheaper/better design for low earth orbit tracking than same money spent on an azimuth elevation unit.

Bad points/Downsides:
It is difficult/impossible to counterbalance the top section, (you can counter balance the lower section) as the way it moves means you end up with a non balanced system, which can put a massive strain on the gearbox. A balanced azimuth elevation system gives less wear and tear and more strength.

At very low elevations it cannot move in azimuth, instead both motors need to move, meaning it can be slower at low elevations, but this is generally not a problem as satellite is “slower” at low elevations

As you now do not have an azimuth rotator, you need to make sure you manually align the motor from North to South, or allow for azimuth calibration in software, if you cannot adjust the azimuth after installation.

It is not really necessary to have accurate tracking at VHF and UHF as the beam width of the antenna is quite high. At high elevations and directly overhead the satellite is a lot closer and so the signal is a lot stronger. For this reason at VHF and UHF if you are off by 20 degrees when it is overhead it does not matter. The same could be argued for elevation rotators. Many argue elevation rotators are not-necessary for VHF and UHF with 6 elements or less, as the need for the gain is only when the satellite is far away at the horizon for example only at elevations below 45 degrees. Some argue that an azimuth-only rotator is OK and just tilt the antenna up slightly so it has gain from 5 degrees elevation to 60 degrees elevation. After 60 degrees elevation the satellite signal is much stronger anyway so receiving a signal is not a problem.

In my case I am receiving at 2395Mhz( microwave above UHF) with a dish with 8 degrees beam-width. In this case I need to track the signal even at high elevations as the dish does not work if more than 8 degrees off signal. I found azimuth and elevation to be too slow at elevations above 70 degrees, so I am testing XY. Another thing to consider is where you live. If the satellite you want to receive never passes directly over your head, then the elevation may never be too high. Take for example the International space station. It never travels very far north or south, so if you live far north or south it will always be at low elevations.

Another problem is that XY controllers do not work with normal satellite tracking software. Instead of Azimuth and Elevation values (which every program uses). To solve this problem you use maths!!
I am still testing the formula, but it takes in Azimuth and Elevation and gives a value for X and Y positions. I can share it with you and software we have written that works with SATPC32 or Orbitron software etc. The extra driver takes the values and converts them, then sends the values to the control box.

Here is the XY rotator I own:

It is a very new model only available in the last 1 year. It is low cost. I bought the very first one, so I am still testing it, currently indoors. I hope to test it more over the next 8 weeks. This uses DC motors, two worm gears, and a 1 pulse per degree feedback.

The gearbox is designed to move very fast, so track fast moving satellites, but it is only designed for light weight antennas. The control box is relay motor control which is harsh on/off click, click control, but a more expensive control box is available (+300 Euro) which is variable speed electronic control.

I hope to put videos on youtube of the XY in the next 4 to 8 weeks.

Here is a link to a DIY build of XY:
You can see the counter-weights for lower motor, but none on upper motor.

So in summary

  1. Elevation rotator is not really necessary for VHF and UHF small antennas, you only need azimuth

  2. XY is harder to balance so damage to gears may be higher

  3. XY is very good for microwave >1Ghz narrow beam width tracking especially if the satellite you intend tracking passes over your head or above 70 degrees elevation

  4. With XY you do not have to flip like azimuth and elevation designs.

  5. The software to control it needs to change Azimuth and Elevation to X and Y values using maths.

Here is why elevation tracking is not really needed: