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RE: Radios for 1.2 GHz operation



This could be easily compensated for by opening up the receiver bandwidth.
Since most ground stations have a very high uplink margin, the increase in
noise bandwidth is insignificant. This has been done on several spacecraft
in the past on higher frequency uplinks. As a matter of fact, the Israeli
Techsat has several uplinks in the L-Band which were used with good results.
Assi 4x1kx/kk7kx



-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Bob Bruninga
Sent: Sun, July 06, 2003 6:26 PM
To: Isaac Waldron
Cc: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Radios for 1.2 GHz operation


On Sun, 6 Jul 2003, Isaac Waldron wrote:

> Worcester, MA.  We are constructing a small satellite, and are currently
> in early design discussions.  We are interested in transceiver or
> separate TX/RX modules (kit or pre-assembled circuit boards) that
> operate on the 1260-70 MHz band for telecommand of our satellite.  We
> are planning to control the satellite with 9600 baud data components, so
> the radios selected must support direct FSK.

I would think that command via 9600 baud uplink at 1.2 GHz is not a
generally good idea because of the HIGH Doppler rate.  You will be
transmitting in the blind hoping to get into the middle of the Satellite
uplink receiver.  Even at 435 MHz this is a skill.  At 1.2 GHz, this
problem is 3 times worse.

You can reduce the problem somewhat by making the IF bandwidth of the 1.2
GHz receiver very wide so that tuning is not so critical, but then you
have just reduced the link budget.  But on the groun dyou have strong
transmitters so that helps.  Just remember to consider all these things...

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html

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