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Subject: Re: HollStar Dishes


Author:
Outsider
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Date Posted: 03:16:07 12/29/03 Mon
In reply to: JVT 's message, "Re: HollStar Dishes" on 13:48:50 12/28/03 Sun
 >
>Hi Outsider,
>
>The Tursat Echo 130+ has two side support arms which
>are supposed to position the main LNB arm at the focal
>point. They are positioned at approx 45 deg points on
>the edge of the dish and meet at a common point on the
>main LNB support arm. The side support arms, though of
>equal length seem to displace the main arm such that
>at what ever axial displacement of the LNB along the
>main arm, Astra2D can not be picked up. The best I've
>been able to achieve is with only one side support arm
>fitted. The side arms do provide a little vertical
>support for the main arm too so when I remove both the
>main arm drops a little. From what your suggesting,
>I'd be better off not having either support arm and
>concentrate on the axial displacement ? Either way,
>the problem also is apparent when I try and place the
>LNB mount where the machined holes are on the main LNB
>support arm and have tried to move the LNB mount right
>the way along the main arm but with limited success.
>My only conclusion is that the machining on the dish
>is very poor as Astra2A/B come through loud and clear.
> It's been very frustrating and am about to revert to
>another 110 TRIAX dish. I have had reports of 24-7
>with the CM120 but have been unable to secure one.
>Tried sourcing a Gibertini dish through Denmark but
>they pointed me in the direction of Swedish companies
>who then said they couldn't help so a bit stumpted !
>It would be great if TRIAX had a larger dish than
>110cm but they've no plans apparently.
>
>If you had any suggestions as to what I'm doing wrong
>I'd really appreciate it. Thanks.

Difficult to say what's the problem, the construction looks sturdy and sound, strange if the dimensions of the arms are not correct. Have you measured the focal length of Tursat vs. Triax dishes, do the F/D values differ much? If they do differ maybe the LNB does not make a good match with the Tursat dish. (I think the best guess of the focal length of an offset dish is to measure the distance from the LNB cap to the bottom rim of the dish.)

Btw, seems the gain values given at Tursat site are totally imaginary, 55dB gain for 1.3m dish at 10.7 GHz would mean an efficiency of around 1500%! ;-)

Because the dimensions of the Triax 110 in fact seem to be only 105cm x 100cm, i.e. it's actually an 1m dish, it migh make some sense to upgrage to 1.2m Channel Master, specified to give 1.8dB more gain, but I think a reasonable step is indeed to go at least to 1.5m.
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Re: HollStar DishesJVT05:13:23 12/30/03 Tue

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