AI3 logo     Moving the earth station antenna
AI3 teammAI3 eventsAI3 researchAI3 publicationsAI3 reports

In January 2000, AI3 traffic on Ku band has been moved to JCSAT-1B satellite. On this occurence, we had to move the antenna dish in AIT.CSIM Logo WelcomeCourses
Faculty, Student, Staff
Projects and reports
Conferences, workshop and seminars
Laboratories and reasearch facilities
Information related to CSIM
Information non-related to CSIM
Address, map, phone, etc.
Search

Rationale

The satellite JCSAT-1B is located 20 degrees further East than the previous satellite (JCSAT-3) used for AI3 operation.

As a result, the antenna is pointed further to the East and at a lower elevation. On the previous location a building was there that would have been an obstacle to the radio beam. So the antennat had to be relocated to a non-obstructed place.

The movie


 This movies summarise the various steps that were acomplished to move the antenna.

Still pictures had been taken every 20 minutes while the work was being done. Edited together, here is the result.

AVI version of this movie is available (40 MB).

Some technical facts

The concrete slab

A 3 x 3 meters, 20 centimeters thick, slab of steel reinforced concrete is used as the base for the antenna. Due to the specific type of the soil, the slab fundation is made of 16 concrete piles, 3 meters long.

To increase the stability, a concrete slab is added that encase the foot of the antenna dish. This second layer of concrete is linked to the base slab with some pieces of steel rod.

Installation of the dish

Four coprer posts, 3 meters long, are used at the four corners of the base slab to provide electrical grounding. Those posts are linked together with 15 sqm copper electrical cable. The antenna foot is grounded this way, as well as every electrical appliances that are used on the outside earth station.

Major problem encountrered was that a missalignment of the antenna panels was creating radio interferences and the signal was degradated. On Ku band, the wavelength of the signal is about 2 centimeters. A missalignment of 5 millimeters represents one quater of the wavelength and cannot be tolerated. After the missalignment was corrected, the normal functionning could be resumed.

Fence

A 2 meters high metalic fence is errected to protect the earth station equipment. Care should be given that the fence is not an obstacle tp the antenna beam.

Given the relatively low elevation (31 degrees) the fence had to be set to follow the exact path of the beam. Here the fence is set with an azimuth of 101.82 degrees East, corresponding to the azimuth of the dish, so the right most part of the fence is parallel to the dish.

The lower part of the figure shows that to escape a 2 meters high obstacle with a 30 degrees angle, the distance to the ground should be 3.40 meters.

Considering that the angle is more than 30 degrees, the distance between the dish and the fence is 4.50 meters and the lower edge of the dish is at 50 centimeters from the ground, enough provision is given so that the fence is non obstrictive.

Monitoring of the link quality shown no modification after the right most side of the fence was erected.

CSIM home pageWMailAccount managementCSIM LibraryNetwork test toolsSearch CSIM directories
Contact us: Olivier Nicole AI3    CSIM    SET    AIT Last update: Mar 2000