Create a New Forum Admin Login Member Login Contribute to Voyager Search VoyForums Help Desk VoyForums Exchange VoyForums Directory/Categories VoyForums Homepage VoyForums News FAQ - Frequently Asked Questions

[ Show ]

Support VoyForums

[ Shrink ]

VoyForums Announcement: Programming and providing support for this service has been a labor of love since 1997. We are one of the few services online who values our users' privacy, and have never sold your information. We have even fought hard to defend your privacy in legal cases; however, we've done it with almost no financial support -- paying out of pocket to continue providing the service. Due to the issues imposed on us by advertisers, we also stopped hosting most ads on the forums many years ago. We hope you appreciate our efforts.

Show your support by donating any amount. (Note: We are still technically a for-profit company, so your contribution is not tax-deductible.) PayPal Acct: Feedback:

Donate to VoyForums (PayPal):

[ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1, [2], 3, 4 ]

Subject: Re: HollStar Dishes Author: Outsider [ Next Thread | Previous Thread | Next Message | Previous Message ] Date Posted: 05:29:23 01/07/04 Wed In reply to: JVT 's message, "Re: HollStar Dishes" on 03:41:23 01/01/04 Thu >>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! > >The F/D ratio values for both the 110 TRIAX and the >Tursat 130 were about 0.58 in both cases. I've not >tried using a feedhorn at all on either of the dishes. > > >In terms of axial displacement of the LNB on the >Tursat I moved the LNB mm by mm along as full a range >of positions as was possible, even with main support >arm attached at the limit of it's fixings. Needless >to say, re-mounting the TRIAX resulted in a return to >viewing. The Tursat dish is soon heading for the tip >I think ! I'll look into an alternative large dish >later in the new year. Thanks for your tips. > >Happy New Year. A bit puzzled! An 105cm x 100cm dish with gain 40.2 dB (i.e. the specifications for Triax TD110) would have efficiency of appr. 66%, an 1.3m wide offset dish with equal gain would have efficiency less than 40%, quite poor indeed. Sure, the Tursat dish wasn't damaged during transport? Larger dents or especially warp can totally ruin the performance. [ Next Thread | Previous Thread | Next Message | Previous Message ]

Replies:

Subject Author Date Re: HollStar Dishes JVT 06:08:58 01/07/04 Wed Re: HollStar Dishes -- Outsider, 03:21:17 01/08/04 Thu Re: HollStar Dishes -- JVT, 06:19:06 01/08/04 Thu