title: “How to calculate Diseqc codes for motorised dish”
date: 2021-03-22T18:32:32
slug: how-to-calculate-diseqc-codes-for-motorised-dish
How to calculate Diseqc codes for motorised dish
by Homer » Sun Jan 19, 2014 12:41 pm
Hi all,
I mentioned I did this in a different thread, and Oberon agreed that I should post it for other forum members.
If your question is “How do I get the Diseqc code to put into TVSource to send my motorised dish to a specific satellite angle ?” then read on.
Basics: Unless you live on the Greenwich 0 degree longitude line, a satellite like Hotbird 13E will not actually be 13E of south from you. To make this clearer, if your home longitude is 13 degrees east, then Hotbird will appear to be due south of you. Unless you live at 0 degrees longitude, you cannot simply send a command to the dish to go 13E of south !
There are a few steps to get the right angle to send to the motor :
1. Calculate the corrected satellite angle from your longitude and latitude.
2. Convert it to hex.
3. Write the full diseqc code to put into TVSource.
Full explanation:
With reference to the official Diseqc guide at Eutelsat.com “positioner.appli_notice.pdf”:
- Angular position codes are in this format E0 31 6E 00 00 {Zeroes, not letter O}
- E0 is the framing byte. E2 is used if a response is required – I only use E0.
- 31 is for polar drives, 32 is for elevation. 30 will send to both – I only use 31.
- 6E is to drive the motor to an angular position – I only use 6E.
- So all of my commands start with E0 31 6E.
-
The final four bits “00 00” are for the angle to drive the dish to:
-
The first bit is “0” for WEST, or “E” for EAST.
- The second and third bit are the hex value of the corrected integer value of the angle. Go to the GAAPS calculator (link below) and enter your lat/long and the required satellite and press “Calculate” http://www.moteck.com/GAAPS.aspx
- Convert the new GAAPS angle to hex. I use the windows calculator (View – programmer calc/ click DEC on Left/ put in decimal value from GAAPS calculator/ Click on HEX on left/ Number is now shown in HEX).
Using this, you would now have (from my lat/long) the following for Astra 28.2E:
Sat is EAST, so first byte is “E”.
Original decimal uncorrected sat angle = 28.2E
Decimal Sat angle from GAAPS calculator (corrected for my lat/long) = 31.9E
Convert integer part to HEX. 31 (dec) becomes “1F” (hex) for the second and third byte.
Convert last fractional part of angle for the fourth byte. We have 0.9 to convert (31.9-31). This table again came from the Diseqc documentation:
User angle/ Hex value
0.0 0
0.1 2
0.2 3
0.3 5
0.4 6
0.5 8
0.6 A
0.7 B
0.8 D
0.9 E
So we have an “E” hex value for the 0.9 decimal degrees.
The full corrected command for Astra 28.2E from my lat/long is now E0 31 6E E1 FE – This is the code that you put into TVSource.
Please note that your southern most satellite may change from E/W or W/E ! I live at longitude 1.178W, and the corrected decimal angle for satellite 0.8W Thor is 0.4E ! This is very important, as you may be using your southern most satellite to align your dish !
Last edited by Homer on Sun Mar 08, 2015 11:37 am, edited 1 time in total.
