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         RX-3a 435.193 MHz (AFC) 4800 bps,RSM
         RX-3b 435.193 MHz (AFC) 9600 bps,RSM
         RX-4  435.041 MHz (digital AFC) RX for RTX-DSP
        Downlink frequency: 145.983 MHz 3 watts (very strong!).
   The downlink can be switched to the following operating modes:
   Mode 1: 1200 bps, BPSK, NRZI,(NRZ-S) (like FO-20)
   Mode 2:  400 bps, BPSK, Biphase-S (Oscar-13 beacon)
   Mode 3: 2400 bps, BPSK, Biphase-S
   Mode 4: 4800 bps, RSM, NRZIC (Biphase-M) (like 4800 bps uplink)
   Mode 5: 9600 bps, RSM, NRZI (NRZ-S)+Scrambler (like 9600 bps uplink)
   Mode 6: CW keying (only for special events)
   Mode 7: FSK (F1 or F2B),e.g. RTTY, SSTV, FAX, etc. (for special events)
   Mode 8: FM modulated by D/A signals from DSP-RISC processor (speech)
        Transponder RM-2 system:
        Linear transponder: inversely heterodyned translator
        Uplink passband             435.123 to 435.043 MHz
        Downlink frequencies        145.866 to 145.946 MHz
        Transmitter output max      10 Watt max.
        Bandwith  (3db)             80 kHz
        Uplink EIRP required about  100 Watts
 Antennas: 435 MHz receiving antenna (shared by analog and digital modes)
 Helix +3 db max RHCP. 145 MHz transmitting antenna: Half wave dipole.
Power supply (up to 100w) comes from the main GEOS satellite  power  supply
system. System RM-1 consumption 47 Watts. System RM-2 consumption 40 Watts
                               Pat Gowen, G3IOR   7 May 1992
19216.SAT
            CHARACTERISTICS of OSCAR-13
   This second functioning Phase III-B  satellite  was  launched  by  ESA's
ARIANE-4 from French Guiana on  15  June  1988  into  a  highly  elliptical
'Molniya' type orbit with a 36,000 Kn Apogee and a 2546 Km Perigee. Due  to
Lunar and Solar effects the orbit is  becoming  more  elliptical,  and  the
lowering  perigee atmospheric frictional drag is set to shorten the life of
this spacecraft. The period is some 11 hours. Four transponders are carried
that are placed on according to ground command control.
   Frequencies for AMSAT-OSCAR 13  (AO-13)
General Beacon      145.812 MHz (PSK,CW,RTTY)
Engineering Beacon  145.985 MHz (PSK,CW,RTTY)
Mode B Uplink       435.423 - 435.573 MHz (SSB,CW)
Mode B Downlink     145.825 - 145.975 MHz (SSB,CW,inverting)
General Beacon      435.651 MHz (PSK,RTTY)
Engineering Beacon  435.677 MHz (PSK,RTTY)
Mode L Uplink      1269.351 - 1269.641 MHz (SSB,CW)
Mode L Downlink     435.715 -  436.005 MHz (SSB,CW,inverting)
Mode J Uplink       144.423 - 144.473 MHz (SSB,CW)
Mode J Downlink     435.940 - 435.990 MHz (SSB,CW,inverting)
Beacon             2400.325 MHz (PSK,RTTY)
Beacon             2400.664 MHz (PSK,RTTY)
Mode S Uplink       435.603 -  435.639 MHz (SSB,CW,FM)
Mode S Downlink    2400.711 - 2400.747 MHz (SSB,CW,FM)
RUDAK Uplink       1269.710 MHz (Inoperative)
RUDAK Downlink      435.677 MHz (Inoperative)
   The 145.812 MHz beacon sends CW telemetry at the  hour  and  half  hour,
RTTY at the quarter and three-quarter hours, and PSK all the  rest  of  the
time. Updated information on mode switching and status is supplied by  this
beacon. The 145.985 MHz beacon is much stronger,  and  is  mainly  used  in
controlled magnotorquing by the command stations DB2OS, G3RUH and VK6AGR.
   The Mode 'B' uplink requirements for A-O-13 are accomplished by using 25
-  50 watts of CW or LSB from any conventional 70cm TX to a 12  X/Y    Yagi
or a 10 turn RHCP Helix  with  azimuth/elevation  pointing.  The    dowlink
requires  an azimuth/elevation pointing 10 element  RHCP  Yagi  or  8  turn
Helix  to  a  low noise pre-amplifier at the antenna feeding any USB 2m RX.
   Mode 'J' requires exactly the  same  antennas  as  for  Mode  'B',  with
reversed transmitters and receivers, with a Low Noise pre-amplifier on  the
70 cm receiver.
   'L' mode needs a pair of 23cm 20 element Quad Loop  Yagis  fed  with  at
least 100 watts of CW or SSB. The downlink needs are as for Mode 'J'.
   'S' Mode needs some 50 watts of 435 MHz CW or SSB  from  the  same  70cm
antenna, and an azimuth/elevation controlled 20 turn  Helix  for  2400  MHz
with a  good low noise front end. A 13cm to 2m or  13cm  to  10m  converter
may  be  used feeding the main station 2 or 10m receiver.
                                       Pat Gowen, G3IOR  25 April 1992
14781.SAT
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