Satellite Tracker Mini

The Satellite Tracker Mini. is a new interface, aimed at the barbecue grill dishes and other small dishes along with small to medium sized yagis on Yaesu G-5400, G-5600 or G-5500 rotators market. This unit is designed to be as low cost as possible, yet offer features never before seen by the satellite chasing fraternity.

 

The Satellite Tracker Mini plugs into the 8 pin DIN connector on the back of a Yaesu G-5400, G-5600, or G-5500 rotator's control unit. One switch of an 8 bit dipswitch selects whether a Yaesu G-5400 or G-5600 (360 degrees azimuth, N centered) or a Yaesu G-5500 (450 degrees azimuth, S centered) is being used. The 8 pin DIN connector provides power and analog voltages proportional to the azimuth and elevation position of the rotators. Two LEDs on the front panel let the user know the status of the interface.

The Satellite Tracker Mini is also plugged into a COM port of a computer running a satellite tracking program. The computer sends azimuth and elevation to the interface, and the interface takes over control of the Yaesu rotator's control unit, activating the up, down, right or left circuitry in the Yaesu controller in response to the desired azimuth and elevation coordinates. The Satellite Tracker Mini also provides variable speed movement of the Yaesu azimuth and elevation motors. Two switches of the 8 bit dipswitch select 4 different azimuth dead zones; another 2 switches select 4 different elevation dead zones; and another 2 switches let the user select the desired variable motion. Dead zone width prevents endless position seeking of a rotator. But too much width leads to inaccuracy, very undesirable when aiming a narrow beamwidth dish. When repositioning the antennas to track a different satellite, you want the antennas to move quickly. But when you are getting close to the satellite, the Satellite Tracker Mini reduces the speed of the rotator to avoid overshoot and subsequent oscillation. While tracking the satellite, especially the Low Earth Orbiting ones (LEOs), the movement will usually be at the slow rate, providing a very smooth motion without rotator destroying oscillation, especially with long yagis. Should the tracking start to fall behind, the Satellite Tracker Mini automatically shifts to high speed to catch up, then returns to the lower pace.

The automatic mode requires data over an RS-232 line operating at 9600 baud. The azimuth and elevation data must be sent out in either EASYCOM I or NOVACOM I format. These two formats send out the desired coordinates as ASCII character strings, accurate to 1/10th of a degree, far more accurate than the Yaesu rotator is capable of achieving.

Setting up the Satellite Tracker Mini

The red dipswitch selects how this interface operates. A dipswitch bit is ON when the switch is pulled towards the numbers (back of the interface) and OFF when it is pushed away from the numbers (towards the front or display). I use a small tool with a blunt hook in it to reach through the rear access hole and push or pull the desired dipswitch. The #1 switch of the 8 position dipswitch on the interface selects whether manual or automatic operation is intended. OFF puts the interface in Manual mode; On puts the interface in Automatic mode. Initially, for calibrating the interface to the Yaesu rotator control unit, put the interface to Manual mode by switching dipswitch #1 off (away from numbers). Normally the Satellite Tracker Mini is left in the automatic mode, and manual operation of the Yaesu rotator is accomplished by switching off the com port bearing updates coming from NOVA.

#2 and #3 dipswitches select the desired variable speed setting. These dipswitches only affect automatic mode. With both #2 and #3 ON, full speed operation always occurs, meaning no slow operation will occur (normal with other trackers, but undesirable). With #2 OFF and #3 ON, Half speed operation occurs when the rotators are within 4 times the programmed dead zone. When #2 ON and #3 OFF, Slow speed operation occurs when the rotators are within 4 times the programmed dead zone. Finally with both #2 and #3 OFF, Crawl speed operation occurs when the rotators are within 4 times the programmed dead zone. I run my Yaesu 5500 & Satellite Tracker Mini with #2 ON & #3 OFF, which provides extremely smooth tracking for me at the "SLOW" rate.

The #4 dipswitch selects whether a 360 azimuth degree Yaesu G-5400 is used (OFF) or a 450 azimuth degree Yaesu G-5500 (ON) is being used. On the rear panel of the Yaesu 5400 or 5500 rotators are 4 holes for accessing 4 potentiometers. Two of the potentiometers are for calibrating the full scale reading of the azimuth and elevation analog meters. The other 2 potentiometers calibrate the full scale reading of the Satellite Tracker Mini. If you have the wrong Yaesu selected by dipswitch #4, you may have difficulty with azimuth calibration!

#5 and #6 dipswitches select the elevation deadzone in steps of 0 (both OFF), 1, 2, and 4 (both ON) degrees. #7 and #8 dipswitches select the azimuth deadzone in steps of 0 (both OFF), 1, 2, and 4 (both ON) degrees.

My preferred settings for my Yaesu G-5500 with 2 long yagis & a PrimeStar dish are:

Automatic Mode - #1 ON, #2 ON & #3 OFF (SLOW), 4 ON, #5 ON & #6 OFF (1 degree elevation dead zone) and #7 ON & #8 OFF (1 degree azimuth dead zone).

Connecting the Satellite Tracker Mini to your Yaesu Rotator

With the rotator off, plug the Satellite Tracker Mini's 8 pin DIN connector into the 8 pin socket on the rear of the Yaesu control unit. Do not connect the Com line to the Satellite Tracker Mini yet. Turn on power to the Yaesu control unit and the Satellite Tracker Mini. The Yaesu rotator should light up as usual and the motors should not move up, down, right or left unless the front levers are depressed. The microcontroller in the Satellite Tracker Mini should start running, as indicated by both the Green and Red LEDs turning on for about 2 seconds, then off. The Satellite Tracker Mini will search for an incoming azimuth and elevation bearing, but not being connected to the computer yet, will find none and after 3 seconds of frustration will turn on the red LED indicating that the Satellite Tracker Mini is now in manual mode. You can use the Yaesu control unit like nothing is attached when the red LED alone is lit. Anytime the Satellite Tracker Mini does not detect a com signal it will automatically switch to this Manual mode indication.

Using the Satellite Tracker Mini in automatic mode

The big picture: After getting the Satellite Tracker Mini connected to your Yaesu and operating correctly in Manual mode, connect the DB9M on the back of the Satellite Tracker Mini to a Serial COM port on the back of a PC. Sometimes the available PC's Com port connector is a DB25M and sometimes it is a DB9M connector. Newer computers and laptops are DB9Ms. Your local Radio Shack store carries a 6' long DB9F to DB9F cable (26-152) that works fine. This cable + a DB25F to DB9M adapter (26-287) will work if your com port is a DB25M. Sometimes you can find a DB25F to DB9F cable at a computer store, but they are rare. Be sure to get a "straight through" cable, not a "null modem" wired cable. When dipswitch #1 is ON, the Satellite Tracker Mini is in automatic mode. The first thing the program does is to look for a valid ASCII data stream in either EASYCOM I or NOVACOM I formats coming to the Satellite TrackerMini. at 9600 baud on pin 3 of the DB9M connector. If it does not get this signal within 3 seconds, the red LED lights while it waits for you to get things going. A tracking program, such as Nova and maybe Wisp, either sends the desired coordinates to the interface over the serial COM line in the EASYCOM I format or the NOVACOM I format.When the Satellite Tracker Mini detects valid bearings, it turns off the red LED and turns on the green LED, indicating that it is now running in automatic mode. The PIC processor compares the received coordinates to the present coordinates, and, when necessary, issues the necessary move commands and sends out UP, DOWN, LEFT, AND RIGHT commands to the Yaesu control box, which then moves the rotator.The EASYCOM I or NOVACOM I bearings provide a 1/10 of a degree accuracy, great for even big dishes, better than most analog precision potentiometers can deliver.

Setting up the Tracking Program Nova

Select "Rotator Setup". In the Interface type box select "Novacom I" or "Easycom I". Select the desired serial port, either COM1 or COM2. If the rotator is the North centered Yaesu G-5400 or G-5600, select the azimuth 180-0-180 box as shown at the left. If the rotator is the South centered Yaesu G-5500, select the 0 - 360 box as shown on the right. If your coax can handle 180 degree elevation rotation, select 180 degrees of elevation. This will avoid an occasional tracking break when your rotator has to reorient due to rotator end limits. Open the baud rate tab and make sure the baud rate is still set to the default 9600 BPS. Click OK.

 

Calibrating your Yaesu to the Satellite Tracker Mini

Select an object that is high in the sky and has an azimuth bearing in the middle of the Yaesu analog meter scale on NOVA. The Sun at noon is handy. Notice the reading on the analog meter. Now turn the com line on and make sure the rotator turns to the correct bearing. Adjust the two external calibration potentiometers marked "OUTPUT VOLTAGE ADJ" so the analog meters read the same as the desired bearing given by Nova.. —a little electronic theory— The Yaesu controller puts out 0 - 5 VDC on the elevation and azimuth pins of the 8 pin DIN socket. The Satellite Tracker Mini is reading these and doing a 10 bit A/D conversion on the value to determine if it needs to move the azimuth or elevation motors.

Use

If your Yaesu rotator snags its coax and is stalled too long, the motor that is stalled can burn up. This happened to me a couple of years ago when using a SASI interface. The stalled motor burned out, the power transformer in the Yaesu control unit burned out, and then the fuse blew. About $350 worth of damage. Nice of it to try to protect the fuse that way. The Satellite Tracker Mini is programmed to continually check for motor commands on with no movement occuring. If it detects this for 20 seconds, then it concludes that you must have a jam and turns off the all motors and blinks the LED of the offending axis.

Make sure your dish is moving reliably before leaving unattended. It is a good normal practice to park the antenna in a position safe from high wind. I switch the tracking box on NOVA to off so the Satellite Tracker Mini switches to manual with the red LED lit, and manually turn my antennas East at 0 degrees elevation. Then I turn the Yaesu control box off.

Updates

The Satellite Tracker Mini uses a small preprogrammed 16F877 PIC microcontroller. Design improvements and corrections are accomplished by simply obtaining a new part from me and plugging it in in place of the current microcontroller. The cost of this service is $10 pp. I wish I could update my '97 Toyota this cheaply!

Repairs

Bad things happen. Lightning Strikes. Units fall. LCDs get zapped by static electricity. If you ever need service for your unit, send it back to me with a $20 check and a description of the trouble. I will either fix & update or replace the unit and mail it back to you ASAP.

 

2/21/2005

My PCB house went out of business and destroyed all of my negatives without warning me. I have no Satellite Tracker Minis left at this tune, and I am not planning on making any more Satellite Tracker Minis.

I have made 20 more of the Satellite ATracker Juniors and currently have 19 availabe for purchase. The Satellite Tracker Junior is $195postpaid USA, $205 USA funds drawn on a USA bank, postpaid to other countries.

 

Dr. Robert Suding W0LMD