Initially it is necessary to find an offset TV dish of a diameter of 85/90cm, with its boom and its support. To adapt it for the reception of AO-40 satellite on 2.4GHz, it is necessary to replace the original TV source by a new helix feed since it is the simplest solution.
The characteristics of your parabola will be given thanks to the worksheet (under EXCEL) of Jean Louis F6AGR (to download)
Once the number of turns of the helix is known (between 6.25 and 8.25) owing to this sheet, you can now make it:
- bare copper wire d=3mm
- one socket type N
- 1 piece of epoxy single sided or an aluminum plated=20cm
The diameter of the helix should be 40mm and for left polarization, it should be wound in the opposite direction of that of a cork screw. Spacing between the turn is 27mm.
the good idea is to roll the wire on a tube whith a diameter smaller than 40mm and when you let wire loose, you will obtain an helix with a bigger diameter, hopefully of 40mm.
Matching is obtained by soldering onto the first turn,a small plate of single sidedepoxy which has the shape of the beginning of the wire of the helix. (see shématics and pictures attached).
Now you can assemble the feed onto the boom of the parabola dish in lieu of the TV feed..
Check the complete assembly using a 2.4GHz source and move the feed on the boom for a maximum signal.