Antenna Look Angles Info

Updated 12 March 2006

More calculators at http://www.satellite-calculations.com

At the poles there it is not possible to receive geostationary satellites.
A geostationaty satellite will only be visible approxematly 74000 meters above the pole.
The theoretical limit for receiving geostationary satellites is near a latitude of 81.91°North/South

 

Polarmount angles

 

Polarity Tilt

Looking towards the satellite.



ERRORS :

Use . (period) as decimal separator.

The scripts uses cookies to store default values like position e.t.c. . Make sure Cookies is allowed on your computer if you wan't this function to work. Error could occur if I need to change the cookie format. Just "OK" the errors an select site & satelite and the Cookie should take the new format.
All calculations is done "on change"

 

SITE LOCATION :
Can be selected from list or the position can be entered manually. The site location from the listbox can be stored as default site location. If you don't find you're site in the listbox the location can be entered manually. 

The first time the calculator is loaded there is a cookie error.  Just select the position again and everytning should be stored in the new Cookie and no error should occur the next time the calculator is used.

SATELLITE ORBITAL POSITION:
Values between 270-360 is converted to 270-360 East Atlantic Ocean Region. 359 East AOR gives the same result as 1 West.


SATELLITE NAME:
Choose satellite name and the angle calculations will be done. Satellite orbitposition can also be entered manually.


OFFSET ANTENNAS
Offset angle on a offset antenna. Not the same value for all offset antennas . Can be changed before angle calculations !


AZIMUTH &POLARMOUNT HOUR ANGLE :
180 degrees=south. 360(0) degrees= north. 270 degrees = West , 90 degrees East

The polarmount hour-angle (x-angle on figure) is 180 deg. when the site longitude and satellite longitude is equal in nothern hemisphere. The hourangle-angle is 360 (or 0...) deg. at the same conditions in the southern hemisphere.

Polarmount hour-angle can be used to calibrate H-H mounts which counts linear pulses/degree. If a H-H mount is calibrated on normal azimuth calculations it will not give correct values.

When a H-H mount is calibrated after the hour-angle it is possible to calculate the counter value for any position.

Click here to see a graph of polarmout x angle vs azimuth at 60 deg. N


POLARITY ANGLE (TILT):
Looking towards the satellite. The turning direction is not equal on all systems. Negtive values is just used to show the turning direction.

A satellite on the same longitude as the receiving/transmitting station will have 0 degrees as horisontal polarisation. Vertical polarisation on 90 degrees clockwise( -90 degrees Counter Clockwise)

On some satellites the polarity angle can be offset from the calculated one.

On the France Telecom Satellites there is a polarisation offset of 20 degrees from the calculated ones.


DECLINATION ANGLE:
For adjusting polarmounts correctly.

UP/DOWN LINKDELAY:
The signal travels at light speed (300 000km/s). The uplink delay in milliseconds is simply the distance to the satellite in km divided by 300
The up/downlink total delay is only correct if the uplink and downlink is at the same site
If its at different sites simply add uplink delays for the two different sites to find total delay

THE TIME WHEN SUN AZIMUTH EQUALS SATELLITE AZIMUTH:
At the UTC/GMT time calculated the sun's shadow direction equals the satellites azimuth direction which will give a good indication in which direction the satellite is located. The date on the computer system is used.
Can be used to make sure there is no tree's in the satellites direction ....

This calculation is disabled for latitudes near +/-4degrees from equator because the calculations does not work. On equator there are only two azimuth angles east (90 deg) or west (270 deg.). Antennas is not pointed after azimuth angle.

At the two periods of the year when there is sun interference , any sunny spot will mean that there is a free line of sight to the satellite.  Suninterference outage times can be calculated using one of the calculators linked at http://www.satellite-calculations.com

 

CALIBRATION OF H-H HOUNT PULSE CALCULATIONS:
Use the lookangles calculator and calculate hourangle for a position far east. Then calculate for a position far west. Find the pulse counter values for this two positions. Now the pulses per hourangle degree can be calculated. Pulse/degree= Difference in hourangle/ difference in pulse counter. Then select a satellite in the lookangles calculator and input the countervalue for that position and the direction which the value increase. As soon as the values is input the calculator calculates hourangle and store the settings in a cookie. Your HH values should then be used the next time you use the calculator.

Some values:
Fibo120cm - 8.686868 pulses per degree
Fibo90 cm - 1.811024 pulses per degree
KTI Proform H180 - 11.4339 pulses per. degree

Be aware that calibrating a H-H polarmount with Azimuth will never be accurate for angles
far west and east. Thats why you should use hourangle.
For small antennas the error can probably be ignored.
The resaon why can be seen
here

The pulses/degree value might also be different with different positioners.

SOME FORMULAS:

Polaraxsis angle=90-Site Latitude-Polaraxis correction angle
Declination from horisontal plane=Declination+Polaraxsis angle

 

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20©06 Jens T. Satre