[NLRS] 10 ghz dish feeds

[Donn Baker]

Hi Ray,
Modifying the dish feed is the way to go, if the feed can be modified. (My
opinion, at least.)  By using the feed that comes with the dish, you assure
yourself of two things: 1st, its at the feedpoint; and 2nd, it illuminates
the dish correctly.  However, not all feeds can be modified (at least easily).

The ones that I've seen modified have had long circular waveguide section
between the horn and the LNB.  They also need "thick" walls.  You remove
the LNA from the back of the WG section, remove the polarization septum in
the WG, and bore it out to 0.75".  Locate an SMA ~0.3" from the back end of
the WG section, and fabricate a plug or short across the backend.  If you
get around to doing this, several of us can help (and would be happy to).
The hardest part is making a "thing" to hold the feedhorn at the feedpoint.
 At least, with the feed that belongs with the dish, you know where the
feedpoint IS.

If you can't do mods, then the best bet is to use the W1GHZ Online Antenna
book and find a feed that will correctly illuminate the dish you have.  A
simple horn, of the proper dimensions, will work just fine, and can be made
from Hobby store sheet brass and tin-snips or (old!) scissors if necessary.
 The 18" Sony dishes than many of us are using are fed with the W1GHZ horn.
 Note that not all DSS dishes are alike... the feed may need to be changed
for each different DSS dish.  Google W1GHZ and Online Antenna Book.

73 Donn
WA2VOI

At 13:47 19-01-04 -0600, Ray J , W9RAY wrote:
>What are people using as a feed on their 18" round offset fed dishes
>(dish network)?
>
>Did I read some ware you can modify the existing dish feed?
>
>Thanks..
>
>Ray J
>
>W9RAY
>www.w9ray.org
>
>
>
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