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JX 90 Cm offset dish working on IS 5 @169 degrees East

JX satellite has been testing many combinations over the last few months in order to launch its domestic IS 5 reception system. During the testing time many equipment combinations have been tested and evaluated before we were confident that the system would provide quality pictures given any weather conditions.

We began our testing some months ago and settled on a 1m dish for domestic reception of IS 5 @ 166degrees east. However 1m dishes are a lot more expensive and 1.2m outrageous in price. So we settled on a 90cm which with careful component selection falls with in ½ a db of a 1m.

 We experimented with several types of LNBF’s some as high as 17 degrees noise figure and some as low as 13 degrees. In the end we decided on a 13 degree LNBF mated with a conical feed horn. Conical feed horns are the feed of choice when it comes to offset dishes. It radiates an axially symmetrical beam with a frequency invariant beam width and very low side lobes which results in a very high efficiency receive antenna system.

The key to the corrugated conical horns efficiency is the technique of corrugating the feed horn wall to optimize the radiation pattern symmetry thus increasing the receive gain. Such a horn has the added advantage that the beam width is relatively independent of frequency. Its primary disadvantage is the diameter of the horn. However given the fact that offset dishes place the feed horn so there is little or no signal blockage.

Comparisons  

Conical Vs Scalar

Conical		Scalar Feeds
Beam width 7-60		Beam width 7-60
Gain in Db 10-26		Gain in Db 10-27
First side lobe level -12 to -16		First side lobe level -20 to - 25
1m Azure shine IS 5 Test dish		Prototype conical horn

Custom made feed holder	90 cm with conical horn and LNBF

JX 90cm dish with 15 degree LNBF mated with a weather proof conical horn

THE PRIZE!

Australia Pacific Network	BBC World

Adhoc channel used for feeds from the US to Australia	Australia Network

Spectrum analyzer screen shots of the active transponders on IS 5

4160 H  (click to enlarge)	3760H  (click to enlarge)

Half Tpr 3991H (click to enlarge)

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