[NLRS] more 10ghz questions

[Baker, Donn B]

Hi Ray,
I can't offer first-hand info (by Jon, W0ZQ did... thanks, Jon), but I can give you some background.

The two numbers (110 and 119) on the dual LNB framework refer to the orbital position of two satellites... 110* W and 119* W longitude. As Jon pointed out, its easy to build a feed horn and mount for the "center" of the feed arm and have only one feed horn.  Its also possible to use one or the other of the feed positions and its LNB (converted for 10GHz use, of course) as is.  In this case, there will be a slight offset when aiming the dish (its called "squint").  The actual aim point of the dish will be slightly offset from the centerline of the dish.  You'd need to figure out how much, and which direction, but only once.  It'll always be the same.

Feedpoint positioning is important, but not critical, at 10GHz.  Within 1/4" is OK.  Closer is better, of course, but that'll work just fine.  Remember that the location is in three dimensions: left-right, top-to-bottom, and front-to-back. The idea that Paul, W1GHZ, had about a knotted string attached to the dish is great.  Shows you EXACTLY where the feed point is located.  (W1GHZ's "Online Microwave Antenna Book," Chapter 5. [<http://www.w1ghz.org/antbook/preface.htm>])

Hope to work you, and the others, on 10GHz this summer from Eau Clare !
73 Donn
WA2VOI/0

> -----Original Message-----
> From: Ray J [mailto:ray at w9ray.org]
> Sent: Tuesday, June 01, 2004 9:14 PM
> To: nlrs at mailman.qth.net
> Subject: [NLRS] more 10ghz questions
> 
> 
> Here's more stuff for the 10 GHz club :-)
> 
>   I was meaning to get some kind of 10 GHz signal here in Eau Claire
> someday..  Now in a a week or so there is to be several 2watt DEMI
> stations in the area. So I feel motivated to work on my pile of Macom
> "stuff" again..
> 
>  I asked about the stock dish feeds on the 18" dish network stuff
> before..  I have recently gotten a hold of a "dish 500" unit. 
>  Which is
> a little bigger..  the problem is it has the dual feeds... has anybody
> tried to use this dish on 10ghz with just 1 of the "modified" stock
> feeds...Will this work? 
>   It has a crapy plastic "holder" that extends out from the end of the
> feed support and holds the 2 lnbs. One says 110 degrees and 
> 119 degrees
> on the other.. not sure what they are talking about here...
>   Would I be better off extending the feed support arm ..centering the
> feed between the 2 that's there now and totally get away from the the
> dual feed plastic thingy???  
>  more questions... what kind of accuracy is required on the dish feed
> alignments... are we talking like 3db per mm or what
> 
> thanks a bunch
> 
> 
> Ray Johnson
> W9RAY
> 
> www.w9ray.org
> 
> 
> 
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