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Re: RE: Prime-Star Dish - Now Sky dish too



The original design should be copied as closely as possible but the width is
probably not that critical. The return loss on my feed was 6 dB without the
shim and only varied between 9 and 12 dB with a shims of various widths
between 3/8" and 5/8" wide.

The way to adjust it without test equipment (other than an AC voltmeter) is
to measure sun noise. Bend the shim upwards and see if the difference
between sun noise and clear sky can be maximized.

73,

John
KD6OZH

----- Original Message -----
From: "Bill Acito W1PA" <w1pa@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, 11 June 2001 14:32 UTC
Subject: [amsat-bb] RE: Prime-Star Dish - Now Sky dish too


> Excellent!
>
> I finished my 2.4Ghz dish helix feed over the weekend. I used 1/4"
> copper tubing wrapped around 1" PVC pipe as a form.
>
> I 've used 5 turns for what I was told was the correct illumination on
> a DSS style (18") dish.
>
> I used W1GHZ's articles to find the phase center of the dish.
>
> The shim that I soldered to the first 1/4 turn is wider than 6 or 8mm
> (more like 10mm). How critical is the width of the shim to the overall
> match (I have nothing I can use to test the match at this point)? I
> used 1/16" Teflon as a spacer between the shim/tubing and the Hammond
> box I am using as a cup.
>
> Bill
> W1PA (openly admits he is a Newbie)
>
> ----
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