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2.4Ghz Sky mini-dish

How to modify a Sky mini-dish so it will work effectivly at 2.4Ghz.

Written by: G4RFR ( FRARS ) Tuesday, 30 July 2002

Click for full size imageA simple but high gain antenna can easily be made from an old Sky mini-dish. The dish that we've used for this article is one from the southern UK region, and is around 35cm minor axis diameter.

A standard tin-can feed horn is used to feed the dish, and looking at the polar plot, we can see that very small side lobes exist, indicating good dish illumination.

The tin can feed detailed on the FRARS pages was used to feed the dish. The SWR adjustment screw in the feedhorn is used when the feed is mounted correctly on the dish feed arm, to optimise the SWR.

Dimensions
Measuring from the bottom of the dish, along the feed arm to the front of the tin can feed should be 243mm. Two feed arm supports are also made from 410mm long pieces of aluminium strip. The feedarms are secured to the tin-can feed by means of a couple of jubilee clips.

Take note of the angle of the existing LNB feed, and ensure that your new feed matches this. Looking along the top of the feed horn, you should aim to see about 1" above the top set of screws on the dish surface.

See the pictures below for further details of the construction.

A polar plot of the dish can also be seen below, showing just how good the front to back ratio is, along with the narrow beamwidth.

Links:

  • More FRARS Wireless LAN articles [Click here]
  • 2.4Ghz tin can feed [Click here]

  • Attachments: (Click to view/download):
    DCP 1131.jpg DCP 1132.jpg DCP 1133.jpg dish polar plot.JPG

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