Satellite Antenna re-positioning circuit

I would appreciate help to do the following.
I have a satellite dish antenna fixed on a floating platform that is anchored/moored in a bay area. Although the sea is always very calm with no movements, with the changing currents, the platform turns in various directions gradually and the satellite dish antenna have to be re-oriented every now and then to tune in the signal. Instead of having to use the remote controller to rotate the antenna a few degrees to compensate for the positional change of the platform, I would like to design an electronic circuit that can monitor the signal level and adjust the azimuth of the dish antenna automatically.
I already have the mechanical/electrical components to do this in place. My satellite receiver has some LED’s to indicate the signal strength. I intend to obtain/extract this signal from the receiver and use this variable voltage to drive my controller circuit. If and/or when the signal level falls below a certain level, one of two relays needs to be engaged until the signal rises to the optimum level. A logic circuit would perhaps be necessary to determine which direction the motor/actuator have to be turned to obtain the optimal signal level. Perhaps a compass sensor unit will be needed to determine the direction the antenna turned while the signal level kept dropping? Please help me with a suitable schematic diagram do this.

I am not an expert, but just offering a couple of thoughts:
As the satellite is geostationary, the reference compass direction is a constant.
therefore you don't need the complication of having your system monitor the signal strength, only the compass direction of the aerial, as the signal will always be strongest in that direction. (And signal strength may also vary somewhat due to weather and atmospheric conditions.)
So your system will only have to detect the deflection of the aerial's direction, possibly via an electronic compass, then apply a signal of so many steps to a servo controller.
However, a decrease of a certain amount in the signal strength could trigger the circuit into action when necessary, to avoid unnecessary "hunting".
I think there are automatic systems available for changing an aerial's direction to pick up different satellites, perhaps such a system might be easily adapted.

Low tech solution: If the water is suffciently shallow, you could just stick a pole in the sand and attach the aerial to that.

I have another suggestion for you in partial agreement with Frank but instead devise a binary code on a disk and attach to side of dish

Similar to how a printer works using light sensors using opt couplers to count ticks, for degrees elevation also horizontal platform movement Include end of travel sensors for full tilt You want geared motors for slow movement through 180 degree’s gear ratio , springs to mind although the LNB is also normally adjustable to some degree and there you would need signal strength meter and ADB conversion

Ideally you need reversible PCM , if you want more control over speed of motor or HBridge driver module and then if you wanted to be smart with this

What you could do is plot co ordinates on LCD and also store Sat Names in I2C memory chip using lookup tables possible so that you can automatically go back N degrees, horizontal and or vertical to pick up other satellites Alternatively you might even consider interfacing this to a PC or laptop again you could include USB port control or Rs232 serial port on you PCB


Device wise something like a 16F877 will do this job quite nicely In fact this could be a very nice little project if you put your mind to this and also very marketable with possible futures in the networking side where from remote premises wifi or even mobile phone you Android driven maybe or even Blackberry where you could control satellites elevation , programme content anywhere in the world Lovely project this

Require some time obviously but worth the effort


Mark www.harrington.force9.co.uk

Thank you Frank. I am very grateful for your reply to my request. I agree with you and know there already would be off the shelf antenna tracking systems that would be suitable for my purpose. The way it would be done perhaps would be as you have suggested i.e. by monitoring the deflection of the antenna direction. I have thought about and in fact tried to make such a circuit using an electronic magnetic sensor connected to an Arduino. Have written some code and I am able to sense the antenna deflection. However the problem is that the magnetic sensor is so sensitive and since my antenna is placed on a huge steel platform, and everything surrounding is steel, the effect upon the sensor prevents me from achieving the desired results.

The low tech solution you have suggested is certainly not applicable to my requirement because the ocean bottom is at about 30 meters deep and the satellite antenna is about 2 meters in diameter. I have made the actuators for the antenna and it done is a way that I am able to turn the antenna system with a touch button on a remote control. That part is already complete. The problem is as the huge platform moves slowly with the changing tide and currents, I have to keep correcting the antenna orientation every now and then.

What I am hoping to do therefore is to build an electronic circuit that can automate the process. My electronic engineering skill is limited but if someone is kind enough to draw up a circuit, I can build it. I believe I have sufficient knowledge and experience to do that much. The design stage is where I need help. I can also identify and locate a suitable feedback signal from within the satellite receiver. I am aware of the possible hunting effect you have explained. But since the antenna needs to be tuned to just one satellite (it doesn't need to be searching for multiple satellites since we are concerned with being tuned on to just one station), I believe a simple logic circuit built into the system could eliminate the hunting effect in my particular situation/requirement.

The logic would be something like this: for example if the peak to peak signal level of the feedback signal coming out of the satellite receiver (at full signal strength) is say 1V, do not actuate the servo if the voltage is between + 0.49V to + 1.0V. If the level falls below +0.5V, actuate the servo in one direction,and monitor the change in voltage level. If it continues to fall, actuate the servo in the opposite direction and keep monitoring the voltage level. When it reaches +1.0V, disengage the servo. And repeat the process only if the signal falls below the reference (< 0.49V). Inserting a time interval of about 30 seconds for the loop may be a good idea perhaps?

Since the antenna moves laterally very gradually over time and since we incorporate a reference range (0.49 - 1), I am wondering if the hunting effect can be minimized/eliminated perhaps? The drawback of this approach will obviously be that the signal quality will drop for a while before the system makes the necessary adjustment. This is OK in my situation.

I have thought about this over and over. Finally I have decided to seek help because my mind is so dumb. I could not think of a way to make this work. I therefore will appreciate your help. Many thanks once again for your thoughts and suggestions.

Monitoring signal strength would still be far more advantageous than just magnetic points but as Frank says it is geostationary

In fact this would really be smart with openGL graphics or even 2G graphics front end with a software , mobile or web interface Nice !! I think i might just uhm pop down and begin a design in relation to this myself

Hello Mark, I am very grateful for your input and support. Your idea of implementing opto couplers to count ticks, for degrees of movement of the antenna itself is excellent.. Although elevation angle is not required (in my case), it would be a very practical way to track the antenna movement (both ways - elevation and azimuth). However signals from these two sensors will have to be used together with actual signal strength monitoring. The opto coupler outputs must be considered as a means of guiding the control stage circuitry. As the platform on which the antenna is mounted keeps on moving (due to ocean currents), there has to be a way of knowing the magnitudes of the movement (in which direction and by how many degrees). Monitoring the signal strength would be the key here because use of a magnetic sensor is going to be difficult in my environment (surrounded by steel structures all around).

I could only wish and hope Mark makes up his mind to go forward with a project to design his seemingly thoughtful 2G front end s/w.

Busy teaching myself opengl as we speak although i quite cant make up my mind whether to use java interpretation c++ interpretation or C sharp but yes I am going to is the answer

Take me a few weeks yet to achieve but never the less I am learning this not only from a Android point of view but also a night rider vehicle point of view see this link

Loads of heavy duty hardcore studying yikes as my maths which I truly wish I was better at needs attention as well Never was much good with this still not to worry ill get there

http://www.harrington.force9.co.uk/KnightRider/Mr.zip

On my homepage a simple opengl application I did for my friends car but alas I have to recompile now since hes just purchased an 8 core processor We did the electrics together on this plus modules for his other friends car in his night rider group originally done in C++ My FIRST BASIC OPENGL PROJECT