From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sainfoin-smtp-out.extra.cea.fr (sainfoin-smtp-out.extra.cea.fr [132.167.192.228]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id E32E33CB37 for ; Tue, 14 Nov 2023 03:50:51 -0500 (EST) Received: from pisaure.intra.cea.fr (pisaure.intra.cea.fr [132.166.88.21]) by sainfoin-sys.extra.cea.fr (8.14.7/8.14.7/CEAnet-Internet-out-4.0) with ESMTP id 3AE8opfD022884 for ; Tue, 14 Nov 2023 09:50:51 +0100 Received: from pisaure.intra.cea.fr (localhost [127.0.0.1]) by localhost (Postfix) with SMTP id E90D1203A93 for ; Tue, 14 Nov 2023 09:50:50 +0100 (CET) Received: from muguet1-smtp-out.intra.cea.fr (muguet1-smtp-out.intra.cea.fr [132.166.192.12]) by pisaure.intra.cea.fr (Postfix) with ESMTP id E011B203A8B for ; Tue, 14 Nov 2023 09:50:50 +0100 (CET) Received: from [10.11.242.12] ([10.11.242.12]) by muguet1-sys.intra.cea.fr (8.14.7/8.14.7/CEAnet-Internet-out-4.0) with ESMTP id 3AE8oow5054474 for ; Tue, 14 Nov 2023 09:50:50 +0100 Message-ID: Date: Tue, 14 Nov 2023 09:50:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: fr To: starlink@lists.bufferbloat.net References: <68f92846-73eb-4183-ad97-79f2aa56b022@gmail.com> <66d7dc64-1b8e-4629-8ffb-6ab2d14d48fb@auckland.ac.nz> From: Alexandre Petrescu In-Reply-To: <66d7dc64-1b8e-4629-8ffb-6ab2d14d48fb@auckland.ac.nz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CEA-Virus: SOPHOS_SAVI_ERROR_OLD_VIRUS_DATA Subject: Re: [Starlink] one dish per household is silly. X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Nov 2023 08:50:52 -0000 Le 13/11/2023 à 21:34, Ulrich Speidel via Starlink a écrit : > > Caution - 250 kW peak sounds more like a horror movie (around 500 W > average powers your average household) but there's an easy > explanation. It's also a good example for why Reddit isn't a good > source of information unless you know and can interpret what it is > that you're looking at. The figures you've seen are almost certainly > EIRP ones (effective isotropically radiated power). And EIRP ain't the > same as power consumption. > > Simple example: Take a 100 W light bulb that radiates more or less > isotropically (same amount of light power in all directions) without > any reflectors etc. When you look at that light bulb, you see 100 W > EIRP. Put a mirror behind the lightbulb, so you now see the bulb and > its reflection, which looks like two bulbs. Makes 200 W EIRP, but it > doesn't increase your power bill. A simple mirror like that has a gain > of 3 dBi. > > At a Ku band frequency of 18 GHz, a 1.5 m diameter parabolic dish has > a gain of over 48 dBi. Each 3 dBi step in there effectively doubles > the number of transmitters you see reflected to you if you're the > receiver. 48 dBi means 16 such steps. So you have to divide the EIRP > of something like this by the "2^16" reflections that this gives you. > If you're having 250 kW EIRP, then the actual transmit power is just a > few watts, and similarly your power consumption is a lot more modest. > > Another way of looking at this is that what goes up (to the satellite > in terms of bits) has to come down (to another ground station / > dishy). That happens via a similar path. So if you'd transmit to a > satellite with anything like even 25 kW actual transmitter power, > you'd also need a similar amount of transmit power at the satellite to > downlink. And you'd have to generate that power up there in orbit. Now > I have solar PV, and I know that generating a measly 5 kW peak takes > 20 panels of around 2 sqm size each. Generating the sort of power > you'd need to transmit at 25 kW would require solar arrays on the > satellite that are more like the size of a football field. Ballpark. > > Thankfully EIRP for a dish of fixed size goes up as a linear function > of dish diameter and transmit frequency as the antenna becomes more > "pointed" as you move from conventional C band to the Ku and Ka bands > used by Starlink. > Also, I'd check the label on the power supply unit of the dish box.  That tells how many Ampers - at a maximum - it can draw. Alex > On 14/11/2023 5:22 am, Inemesit Affia via Starlink wrote: >> You have to size power equipment for max power plus a percentage >> regardless of current traffic needs. >> >> Look for the ANATEL docs on Reddit you'll see it there(per dish at >> least). Or search the NASASpaceflight forum. >> >> I think it's 250kw peak. Could be 25kw instead can't remember right. >> But each dish is more than 5kw and there's other equipment than dishes >> >> Nov 13, 2023 5:10:27 PM J Pan : >> >> is the power consumption related to traffic volume? currently the >> traffic is very light >> https://www.reddit.com/r/StarlinkEngineering/comments/17k3jas/intergs_ground_station_satellite_links_much/ >> >> -- >> J Pan, UVic CSc, ECS566, 250-472-5796 (NO VM), Pan@UVic.CA, >> Web.UVic.CA/~pan >> >> On Sun, Nov 12, 2023 at 10:40 PM Inemesit Affia via Starlink >> wrote: >> >> >> It's kinda expensive to run. Likely 75KW peak. >> >> Check the power requirements for a regular gateway and divide >> by two. >> >> Might be useful for Taiwanese Islands though >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink >> >> >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink >> > -- > **************************************************************** > Dr. Ulrich Speidel > > School of Computer Science > > Room 303S.594 (City Campus) > > The University of Auckland > u.speidel@auckland.ac.nz > http://www.cs.auckland.ac.nz/~ulrich/ > **************************************************************** > > > > > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink