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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Quick numbers from RF Ham Design Mesh dish kits with 2.8mm screen for operation up to 10 GHz (which you may already have):<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">2.4m -> ~40lbs (and is about the weight of my spun aluminum dish at 2.3m, maybe a bit more)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">3.0m -> ~70/80 lbs (there are two variants)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">4.5m -> ~172 lbs<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Those numbers include feed support arm weights. The numbers do not include mounting brackets (which might be pretty beefy) or the actual weight of a feed and feed
mounted electronics (which should be fairly small at 10 GHz).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Those numbers also do not include the (usually required) counterbalance weights. As a very rough first cut, I would say whatever the dish weight is, add 3dB to
account for the counterbalance (lever arm distance, center of mass of the dish and some geometry math could refine this estimate, I think it’s a bit more than required). So if the rotator is rated for a 100 lbs (static weight), a 2.4m/8ft dish is probably
going to be about the largest that can be supported. Might want to add a little margin there (or maybe the margin is in more refined math for the counterbalance requirements already, and 3dB more weight is too much with reasonable arm length).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">2.4m is a lot of gain and a narrow beam (~1 deg at 10GHz). So depending on the target pointing accuracy requirement of the system (rule of thumb I heard somewhere
is 1/10<sup>th</sup> the beamwdith of the antenna as a minimum requirement), that might be OK.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">To summarize, I think 100lbs sounds about right for the total static weight handling of the dish, brackets, feed arms, feed/feed electronics. If the pointing accuracy
is around 0.1 degrees, then the rotator would be able to support up to about a 2.4m reflector, with counterbalance, fairly accurately but might be pushing the limits of the systems. If the pointing accuracy can be improved better than 0.1 deg, that would
increase confidence that a 2.4m size would be reliably handled. Somewhere in there is probably a needed analysis for accelerations/velocity capability of the system to make sure it can keep up with LEO az/el angular rates fast enough. Whipping 100 lbs around
quickly might be tough. As a point of reference my personal Spid RAS/HR is slowwww with my 2.3m system, but the VTGS Spid Big-RAS/HRs can keep up with LEO angular rates with an RF Ham design 3m antenna no problem (only tested up to S-Band frequencies though,
so not sure how stable it would be for 10 GHz LEO tracking).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Hope this helps.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">-Zach, KJ4QLP<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">--
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Research Associate<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Aerospace & Ocean Systems Lab<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Ted & Karyn Hume Center for National Security & Technology<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Virginia Polytechnic Institute & State University<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Work Phone: 540-231-4174<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Cell Phone: 540-808-6305<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Ground-Station <ground-station-bounces@lists.openresearch.institute>
<b>On Behalf Of </b>KENT BRITAIN via Ground-Station<br>
<b>Sent:</b> Thursday, January 9, 2020 4:52 PM<br>
<b>To:</b> Michelle Thompson via Ground-Station <ground-station@lists.openresearch.institute>; Michelle Thompson <mountain.michelle@gmail.com><br>
<b>Subject:</b> Re: [Ground-station] Checking some assumptions about dish weight<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Helvetica",sans-serif">Usually 60-75% of the weight is in the mount and positioners.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282A">On Thursday, January 9, 2020, 2:20:31 PM CST, Michelle Thompson via Ground-Station <</span><a href="mailto:ground-station@lists.openresearch.institute"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif">ground-station@lists.openresearch.institute</span></a><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282A">>
wrote: <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282A">This question is related to the open source tracking station project.<br>
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I've looked at a lot of dish catalogs and eBay sales. <br>
<br>
For big dishes, for use up to 10GHz or so, would it be reasonable to specify 100lbs (45kg) for the weight? I'm seeing a lot of dishes up to 8ft that are less than that. We have to pick a number for the mechanical designer.
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Another breakpoint seems to be 250lbs (115kg). <br>
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-Michelle W5NYV<o:p></o:p></span></p>
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