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PA3GJE > SATELLIT 28.11.03 14:16l 70 Lines 2453 Bytes #999 (0) @ WW
BID : SBDLX0PAC004
Read: GUEST
Subj: swl&VUSatp2
Path: DB0FHN<DB0RGB<DB0FSG<HB9EAS<DB0CZ<DB0GE<LX0PAC
Sent: 031128/1303z @:LX0PAC.LUX.EU [Bourscheid JN39AV] bcm1.43l
From: PA3GJE @ LX0PAC.LUX.EU (Leon)
To: SATELLIT @ WW
X-Info: No login password
from : pa3gje @ lx0pac.lux.eu also via ve3mch.ampr.org
to : sat@ww, amsat@ww
sub : SWL HAMSAT, VUSat
SWL&VUSat ( HAMSAT ) part2
A little bit abt up&dwn frequencies of VUSat, HAMSAT.
HAMSAT : downlink center 145.90 MHz, uplink center 435.25 MHz,
bandwidth 0.060 MHz.
So we know :
145 MHz : 145.870.000 - 145.930.000
435 MHz : 435.220.000 - 435.280.000
this delivers a calc factor T ( f,T osc ) :
T (1) = 581.15 INV transponder
T (2) = 289.35 NON INV transponder
Some more :-) calculations deliver :
A1 RX=T-[TX+DS70]+DS02
B1 TX=T-[RX-DS02]-DS70
DS02 is 2m doppler and DS70 70cm doppler value.
DS02=DS70/3 and DS70=DS02*3 .....
An example : suppose somebody transmits on 435.25 MHz ( center band ) and the
LEO doppler value ( on 70cm, DS70 ) for that moment is -8 kHz ( a LEO LOS
situation ) : we will see the coming back signal ( downlink ) on the
ground station antenna :
formula A1 RX=T-[TX+DS70]+DS02=581.15-[435.25+(-0.008)]+(-0.008/3)=145.90533etc. MHz.
Because doppler values are changing less if existing LEO AOS/LOS situations,
sometimes it could be convenient to make such a calculation as above.
Further it is possible now to compose a satellite mode B ( in this case hi )
TRANSLATION CHART, perhaps with doppler shift compensation if you want. Some
very good results ( examples ) you will find in THE SATELLITE handbook ( ARRL
edition ISBN 0-87259-658-3 4-3fig4-2 & 4-4fig4.3 .....
You could use it outside, without a prgr. etc. etc.
Concerning a NON INV transponder :
A2 RX=[TX+DS70]-T+DS02
B2 TX=[RX-DS02]+T-DS70
An example : suppose somebody transmits on 435.25 MHz ( center band ) and the
LEO doppler value ( on 70cm, DS70 ) for that moment is -8 kHz ( a LEO LOS
situation ) : we will see the coming back signal ( downlink ) on the
ground station antenna :
formula A2 RX=[TX+DS70]-T+DS02=[435.25+(-0.008)]-289.35+(-0.008/3)=145.88933etc. MHz.
Remark : both uplink frequencies are the same ( example 1 and 2 ), center up, but
the downlink signals are different. The signal, when it arrives at the transponder
antenna, is not center anymore ( because of the doppler influences ).
Both transponder types will only work the same at f=center.
55 with the satellites, 73 Leon ((-,O)) PA3GJE.
pa3gje@lx0pac.lux.eu
pa3gje@amsat.org
http://www.qsl.net/pa3gje
http://www.qrz.com/database?callsign=pa3gje
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