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RE: Satellite ranging



So if I do this on our local voice repeater which is 40 kms away,

299 792 458m = 1 second (speed of light)
     40 000m = x second (our repeater)

cross mulitply

40 000 / 299 792 458 = 1.3342 x 10-04 (seconds)

which is 0.00013342 seconds or 133 us to get to the repeater.

So the round trip should be 266 us roughly. (delay due to gear ?)

Sound right ?

Can I do this with a 100 meter roll of hook up wire ?

299 792 458m = 1 second (speed of light)
        100m = x second (our roll of wire)

which is 3.335 x 10-07 (seconds)

which is 0.3335 us - my cro should measure that.

Andy Vk4TEC


-----------------------------------------
Andrew Rich - VK4TEC
Satellite Ground Station for PCSAT2
vk4tec@tech-software.net
www.tech-software.net
Brisbane AUSTRALIA

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of g3ruh R Miller
Sent: Monday, 10 October 2005 5:04 AM
To: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Satellite ranging


On 2005 Oct 09 Andrew Rich wrote:

> Has anyone done ranging experients, using a two channel CRO and sending a
> signal via a satelite and working out
> the slant range from delay ?

Satellite Ranging
-----------------
Yes. All Amsat P3 satellites had/have ranging capabilities.  Either the
flight
computer could regenerate and return a 400 bps signal, or a transponder
could return anything.  The resultant range measurements were used to
determine the satellite's orbit, and will do so again for P3E.

When AO-40 was working you could send pulses through the transponder, and
watch the changing delay.  Pulse-at-a-time measurements are of course noisy,
and you can do far better by sending a rapid stream of pulses.  These can be
faster that the round-trip time allows if you make the pulses a unique
stream
of +pulses and -pulses, which manifests itself as a quasi-random data
stream.
With this you can, with suitable mix of hardware and software, get both
uplink pulses and downlink pulses "into" a computer and do all the time to
range range conversion automatically to remarkable accuracy (sub km).

An article about this is at:

  http://www.amsat.org/amsat/articles/g3ruh/123.html

Hope useful.

73 de James G3RUH  - (AO-10), AO-13 and AO-40 command station

--
==========================================================================
    James R Miller      WWW/PGP:     http://www.jrmiller.demon.co.uk/
  Cambridge, England   Stardate:        2005 Oct 09 [Sun] 1902 utc
==========================================================================
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