[Not so] Recent News on AO-27

[Or jump to Grids/States/Provinces worked on AO-27 or arranging a sked.] This information is fairly old, but still remains fairly current. Check the AMSAT news, for current TERP states and other useful information.
To: amsat-bb@AMSAT.org
Subject: AO-27 TEPR States
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As of 9/21/97 the TEPR State are set to:

Tepr 4 - 12.5 Minutes
Tepr 5 - 18.0 Minutes

Current Infomation about AO-27 can be found at www.umbra.com

- Michael
From AMSAT news, August 17, 1997.
(Uplink 145.85 MHz FM, Downlink:
436.792 MHz FM (As of April 1, 1997)


The TEPR States are defined as follows:

Tepr 1, Started when the satellite Enters the Eclipse
Tepr 2, Started at (tepr 1 time) after the satellite enters the eclipse
Tepr 3, Started at (tepr 1 time) + (tepr 2 time) ...

Tepr 4, Started when the satellite enters the Sun
Tepr 5, Started at (tepr 4 time) after the satellite enters the Sun
Tepr 6, Started at (tepr 4) + (tepr 5) ...

TEPR states 1,2 and 3 happen during the Nighttime
passes and TEPR states 4,5 and 6 happen during the Daytime passes. 
occur during EVERY pass, not just over the U.S.A.

The times assigned to the TEPR states are chosen for the health of the
satellite over operation convenience.  Therefore, during parts of the year
the satellite will turn on late or turn off early as seen by ground

Users are asked not to transmit on 145.85 MHz if they do not hear the
satellite's downlink so as to avoid possible interference to other
satellite uplinks and downlinks on adjacent frequencies.
[ANS thanks Michael Wyrick, N4USI, AO-27 Control-op, for this update.]

[IMPORTANT: AO-27 has a sensitive receiver and unless you have a pre-amp, AO-27 will hear you long before you hear it. At least over North America, there is almost always activity on daylight passes, so please wait until you're sure you'll be able to copy callsigns before transmitting. Be brief; just give your callsign and grid square, and one of the regulars will come back to you, especially if you have an uncommon grid square. -- KD6PAG / 03-Jun-97]

From SpaceNews, June 3, 1996.
As of 27-May-96 at 17:00 UTC, AO-27's transmitter schedule is as follows:

20 minutes after entering the sun, the transmitter turns on at normal power
18 minutes after turn on, it shuts off. (38 minutes after entering the sun)

TEPR STATE 4 = 20 minutes, 40 Units
TEPR STATE 5 = 18 minutes, 76 Units 

To clear up any misunderstanding, the Amateur transmitter on board 
EYESAT-1 known as AMRAD-OSCAR-27 CAN and DOES from time to time run
off batteries.  The reason for an 18 minute window over latitudes equal
to most of the U.S. is a limited power budget for the Amateur payload.  
EYESAT-1 runs experiments for Interferometrics, Inc. in Chantilly, Va.  
There is not enough power left over to run the Amateur transmitter full

Ocassionally when AO-27 control operator Michael Wyrick, N4USI, has
the chance to work AO-27 during night time passes, he will turn the
experiments off and turn the Amateur payload on.  This is why ground
stations can hear and work it at night, mostly during weekends.

On 02-Feb-96, Mr. Wyrick had a skydiving accident that resulted in a
broken pelvis in six places.  This kept him from changing the TEPR
(schedule) for several months.  With the sun's movement during the
summer, TEPR schedules need to be uploaded every few weeks to keep
the Amateur transmitter turning on for all of the pass for stations
at mid US latitudes.  Michael is happy to report that with the help
of fellow amateurs, he now has a working control station located at
his home.  This now allows him to upload schedules when needed.

AO-27 is a secondary payload onboard EYESAT-1, and demands on system
resources need to go the the primary payload.

Jeff, KO6RD in Merced, California reports working N7SFI in Utah last
Thursday who was making satellite contacts through AO-27 while standing
in a parking lot with a dual band HT.  Many others have been able to work
AO-27 without receive preamplifiers or high gain antennas.  Stations have
also been known to work this satellite from their automobiles, and slow
scan television contacts have also been attempted.

AO-27 accepts FM uplinks on 145.850 MHz, and downlinks on 436.800 MHz.

[Info via N4USI and KO6RD]
[Yes, some mobile rigs (such as my Yaesu FT-5100) will receive AO-27, especially away from urban QRM, albeit, with alot of fading. If you try this route, please make sure you can copy callsigns before transmitting! -- KD6PAG / 03-Jun-97]

From the AMSAT-BB mailing list, 31 July 1997:
  Here is the correct information on AO-27 about packet vs. voice operation.

 What is the satellite called?
  Object 22825 is called AO-27 by the Amateur and Eyesat-1 by the commercial 

 When can AO-27 operate?
   The Satellite contains batteries and solar panels and is could run the
transmitters during ANY portion of a pass.  Due to power budget limits, the
AO-27 Transmitter can not run all the time. If it did, the batteries would
run down in a week's time.  Therefore the AO-27 TX is on only for 17 Minutes
a pass.  This is a difference in the Amateur and Commercial sides.  The 
Eyesat-1 commercial Transmitter could be left on all the time at different
power levels.

 What Hardware is on-board?
   The Satellite contains 3 Transmitters and 7 Receivers.  It also has 5 FSK 
demodulators, 2 GMSK demodulators, 2 GMSK modulators,1 G3RUH modulator, 1 
AFSK modulator and 3 analog modulators for sending received analog to any of 
the 3 transmitters.  There is NO DSP on-board.

 What are the differences between the Amateur and Commercial sides of the 
  For all practical purposes any RX can be switched to and demodulator and 
any TX can be switched to any modulator. AO-27 and Eyesat-1 can both be used 
to send Packet (any of the modulations the modems support) and Voice.  There 
is no real difference from the Amateur AO-27 side and the Commercial Eyesat-1 
side as far as modems are concerned.  Both AO-27 and Eyesat-1 can run the 
AO-16 microsat style software and can be used as a digital-store-and-Forward 
satellite.  The Commercial TXs have 16 power levels and the Amateur TX has 
only 4 levels.

 What can the Analog mode do?
  The Analog mode simply hooks the discriminator of the Receiver to the 
varactor of the Transmitter.  Tests before launch showed about 30KHz can be 
passed through in this mode.  If you can fit it into 30KHz (well almost) you 
can send it through AO-27.

  Slow-Scan TV, 1200 baud GMSK, 1200 AFSK, Lets not forget Voice, 
DOVE (DO-17) Telemetry and a host of other modes have been sent through 
AO-27 in Analog mode.

 What should we be sending through AO-27?
  AO-27 in Analog mode is not a very good way to send Packet.  There are 
enough packet satellites out there that do a better job.  Voice is the 
preferred use as it reaches the most people.  But from time to time, other 
modes should not be ruled out.  The slow-scan TV worked very well, and I for 
one like to see new ways to use the satellite that we did not think of when 
we built it.

 So if we should not use packet, WHO is sending packet to AO-27?
  1) The uplink 145.850 is very close to other satellite uplinks. LO-19 has 
Uplinks at 840 and 860 that pass through the Analog passband.  When LO-19 is 
in the sky at the same time AO-27 is, you can hear uplinks from ground 

  2) There is ground based packet station that don't pay attention to band 
plans, it comes up on the Analog passband. (you can decode some packets with 
a TNC to see who).

 What can we do?
  Just enjoy the satellite when you can.  Most people enjoy making contacts 
and don't worry about the interference picked up by the receivers.  If we 
had built deaf receivers so only 5 KW EIRP could make it into the satellite, 
there would be far less contacts from low power stations and many of you 
would never have known that AO-27 was available.

  If you do happen to decode a packet callsign, just drop them a nice note.  
I have called several stations that were using packet and some that were 
using simplex voice that never knew they were operating on a satellite 
frequency.  If you demand they move, you might be surprised just how strong 
their signal becomes in the following weeks.

 Final Note.
  Please LISTEN before you transmit.  If you can't hear the satellite, you 
can't make a contact and you will keep everyone else from making one.

- - Michael

(* Michael Wyrick                                                         *)
(* N4USI                                                                  *)
(* AO-27 Control Operator                                                 *)
(*                                                                        *)
(* PGP-public key can be found at www.umbra.com                           *)

KD6PAG grid squares via AO-27 as of 27-Sep-97:

With several contacts awaiting written confirmation (including FL, VA, and AL)... Usually operating from CM87; with CM86, CM88, CM97 or CM98 available upon request.

If you want to try to work me, first check the predictions for your locality against mine, which are UTC. Bear in mind that because of TEPR shutoff, certain times of the year, i'm not able to work more than few minutes past MEL; that local clutter (and antenna pattern for overhead passes) will sometimes cause bad fades for me just before MEL, and that weekends are so busy sometimes that it's hard for me (or you) to get through. So maybe I'll hear you on AO-27, and if i don't, there's a good chance the 'Utah contigent' will... Often i'm on most transcontinental and Pacific passes these days (at least, when i can keep up with sending QSL cards).

Now, if that doesn't work or you want a more formal schedule on AO-27, send me e-mail (with your location if it differs from the on-line callbook). I'll run predictions for both localities and you can pick the specific pass(es) you want to try for. I used to work Mir/SAFEX when it worked, but alas, that is no more and currently, the ISS is primary packet, with occasional voice contacts with the resident astronauts.  -- KD6PAG

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