From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rellim.com (rellim.com [204.17.205.19]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id CABCE3CB35 for ; Sat, 12 Jun 2021 15:20:21 -0400 (EDT) Received: from spidey.rellim.com (unknown [IPv6:2001:470:e815::19]) by rellim.com (Postfix) with ESMTPSA id E850B20084B for ; Sat, 12 Jun 2021 12:20:20 -0700 (PDT) Date: Sat, 12 Jun 2021 12:20:14 -0700 From: "Gary E. Miller" To: starlink@lists.bufferbloat.net Message-ID: <20210612122014.5338f636@spidey.rellim.com> In-Reply-To: <7759ff5d-9d0e-4dd5-8b05-5ea5646b7b5c@Spark> References: <950B8EAF-90B9-41A6-951D-91821F591D41@teklibre.net> <01a7bed2-6f49-3d7d-eb5a-209031ee8070@gmail.com> <391A8897-5A1F-424A-9DD0-01B66824887B@teklibre.net> <31411.1623506452@dooku> <7759ff5d-9d0e-4dd5-8b05-5ea5646b7b5c@Spark> Organization: Rellim X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/Om6/+DrrlVA.2fYhA1jJjxo"; protocol="application/pgp-signature"; micalg=pgp-sha512 Subject: Re: [Starlink] Microstate Accounting and the Nyquist problem 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: Sat, 12 Jun 2021 19:20:21 -0000 --Sig_/Om6/+DrrlVA.2fYhA1jJjxo Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Yo Mike! On Sat, 12 Jun 2021 21:05:19 +0200 Mike Puchol wrote: > Duh=E2=80=A6 you are correct, I was still on the desktop-sizes ones=E2=80= =A6 but > would you need one? What I can find is not cheap. It would be > interesting to work the math eg for Doppler shift compensation which > could require better accuracy than a =E2=80=9Cnormal=E2=80=9D GPS synced = timing > source. GNSS satellites have many atomic clocks. Usually three, to start with. Some Ceasium, some Rubidium. They know what time it is, but not where they are. Solar winds psuh them around by several meters. So ground stations bounce lasers off the sats to reduce the positiion uncertainty. After that, the Ionosphere and Troposphere uncertainty dominates. The doppler can be +/- 10Khz, but the receiver bandwidth is about 250 hz. So you need to know the doppler before you can lock on the signal from the bird. Starlink must have even greater doppler, compensated by a wider receiver bandwidth. No way you are improving on what the GNSS folks do. A lot of black magic invovled. For well under $100 you can get a receiver solution that will asily surpass the clock resolution in a Linux host (<50 ns). The actual PPS will be around 15ns. That can be improved with a bit of external hardware. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 gem@rellim.com Tel:+1 541 382 8588 Veritas liberabit vos. -- Quid est veritas? "If you can't measure it, you can't improve it." - Lord Kelvin --Sig_/Om6/+DrrlVA.2fYhA1jJjxo Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIzBAEBCgAdFiEEDImNR/2vUKZZKLG0LmvF3i7oaj4FAmDFCO4ACgkQLmvF3i7o aj4GHg//c2Lk86hD7HqI6cXsseCRJmQZDLf1297o3Ar3M1PDD2M2XncqTwnhMZd5 R4wV2eb+90OGzckXMSl0YAOtVmLgopG8Ih7JY0y8Y/q43VOxGhSf8CuNCICMAVbT EYHyrIDj0Tx32ZaCMbk/+0MhFAkCZkwuTrnAYrM8zXSqloJB/CJKlbyWHpK3Hpsu dVDs4N6orvnmIXOjANYSTWjcKvh/S3edE4GupB2h0oTNQ7iHCr8ErDSAr/HlKVmn K5ebvTyyOsh4RHqHHL+ICRqIdMlWgx7eQRudcA30llRgNXWvFqGvBTI/MTC0Dep+ vXtmzlWoClGQWBe5YGh5BPlkPdRPOAZysEobadInWky1TYSHTi7rP/0DuZMTw7w2 MyjKHBv3RYiKMUyCXpjaCPOl8FRjBRngB1NwncI6BT0EAbsGqTED7VcvDpqcLcwj tq2P6FKpnhPJEcn/LaRn3c5mJkLeDedovHUimJUKd3CnkqFdj/ruiriUwD6QMf5i HVOvdnRM9NhV3dRghw+5ZozZJ0ww3SbkTB3AWXqbMvaxGhg7guwMB8JKLhV5Y+Pw DIFLkAaVjCPXxl2wWsXU3m/qysdYfzEcgLFD96YYiKHf2CvXA2P06YN7bRzd3qJS bAAS8z1+eLSZ9WU26y3efzdY7MuPEjexin0H4LKp23fZyL+/n1g= =bKoC -----END PGP SIGNATURE----- --Sig_/Om6/+DrrlVA.2fYhA1jJjxo--