| Subject: Re: HollStar Dishes |
Author:
Outsider
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Date Posted: 05:52:12 12/30/03 Tue
In reply to:
JVT
's message, "Re: HollStar Dishes" on 05:13:23 12/30/03 Tue
>
>Yes, I'm very dubious about the Tursat claims. I'd
>tried measuring the focal length and diameter and
>checked the ratio and there's not much in it. I'll try
>one last experiment with the dish. I'll turn the main
>LNB support arm around so I have a longer length to
>play with for axial LNB displacement. (The end fixed
>to the bottom of the dish has two bolt holes, if I use
>just the outer one this will give me another 4" to
>play with on LNB axial displacement and I can check
>out your theory on LNB positioning from the front face
>of the dish. Otherwise, I think the TRIAX 110 will
>have to serve as my interim solution until I can try
>out a CM120 or perhaps a 1.5m ..... but I'm a little
>dubious about going for the Hollstar 1.5m - Firstly as
>the shipping quoted is very expensive and secondly it
>is a bit of an unknown quantity.
>[The LNBs I've tried out so far include the EuroStar
>ESKD-T2 Twin O/P 0.5db, Invacom TWH-031 0.3db Twin
>O/P, Invacom Single 0.3db MTI AP8-T2, Acer 0.6db all
>with Panasonic TU-DSB30s, Panasonic TU-DSB20, Pace
>2500S3, Grundig 210/2 and an Amstrad DRX100. The
>Invacom twin is the best and gives marginally better
>results than the EuroStar.]
>
>Thanks for the feedback, I'll keep you posted on my
>experiment. Cheers.
>
>JVT
What did you mean by "I'd tried measuring the focal length and diameter and checked the ratio and there's not much in it", do you mean that the values were equal in both dishes? I measured my Triax TD88 (well, actually a noname one, but the construction easily reveals the origin) and got F/D=0.6, quite ordinary value. I was just thinking that if Tursat has essentially different F/D, it may need different feed/LNBF to work well.
Please, note that the axial placement of the feed is very critical, moving it something like one wavelength, about 3cm (I do not have any reference readily at hand to check the exact value) in either direction makes a complete null, moving it further away gets other minimums and maximums, you should not try to move it too much!
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