Dear Sumbandila Team,
Congrats and Thanks for getting SO-67 back on the air again. Will certainly look forward to work through the Satellite again.
We fully understand the requirement for activation during Day time passes. Since most of us here in India use simple "Fixed" antenna setups - please consider the Higher Elevation Angles ahead of the lower ones - if all the passes cannot be activated. Personal request from the small group here in South India.
The Sked required for the Day Passes over Indian Subcontinent is a follows:
Satellite Start time IST START UTC Start AZ Peak AZ Peak EL END - UTC End Az SUMBANDILA (SO-67) 22-Jun-10 08:31:56 03:01 31 101 20 03:12:51 167 SUMBANDILA (SO-67) 22-Jun-10 10:06:07 04:36 338 282 11 04:45:42 229 SUMBANDILA (SO-67) 23-Jun-10 08:13:52 02:43 43 99 10 02:53:27 153 SUMBANDILA (SO-67) 23-Jun-10 09:46:51 04:16 350 280 21 04:27:41 215 SUMBANDILA (SO-67) 24-Jun-10 07:56:20 02:26 59 98 4 02:33:30 135 SUMBANDILA (SO-67) 24-Jun-10 09:27:50 03:57 0 278 41 04:09:25 203 SUMBANDILA (SO-67) 25-Jun-10 09:09:03 03:39 10 196 88 03:50:53 191 SUMBANDILA (SO-67) 26-Jun-10 08:50:28 03:20 20 106 41 03:32:08 179 SUMBANDILA (SO-67) 26-Jun-10 10:26:04 04:56 324 284 4 05:03:19 246 SUMBANDILA (SO-67) 27-Jun-10 08:32:08 03:02 31 101 21 03:13:03 167 SUMBANDILA (SO-67) 27-Jun-10 10:06:21 04:36 338 282 10 04:45:51 229
Request an early confirmation so that the same can be published among the Local Hams and hope good activity from India.
Further sked for the next week will be emailed on Friday before 1200Z
Madhukar – VU2MUD Yahoo Mail: vu2mud@yahoo.co.uk Gmail: vu2mud@gmail.com General Blog: http://vu2mud.blogspot.com Satellite Blog: http://workingtheoscars.blogspot.com On Mon, Jun 21, 2010 at 7:34 PM, Jan-Albert Koekemoer < jan.koekemoer@sunspace.co.za> wrote:
Hello
After much delay we are now in a position to re-activate the SA-AMSAT payload schedules on a regular basis again!
During the downtime we conducted several experiments in order to investigate possible alternatives for the “cut-off” problem experienced by many at the end of last year / beginning of this year. The cut-off is caused by SW running on piggyback electronics that continues to gate the received audio onto the transmitter for about 3s after a specific ground transmission has ended, whereafter the received audio is cut off. The SW then waits for the next ground transmission with a valid “transponder” tone embedded, before gating the audio onto the transmitter again. So if a second transmission starts within the 3s “tail” period, it will be cut off when the 3s expires. Listen to this mp3 recording as an example: http://tinyurl.com/38vvg3o* *
Unfortunately the piggyback electronics does not have reprogramming functionality, so we are not able to change the SW. We did however manage to implement a mechanism on the satellite transponder (used by the piggyback) that should be of some assistance when using the payload: the PTT of the transmitter now STAYS ON for the duration of the payload activation (i.e. 15 min), regardless of a valid “transponder” tone received. Note that this does not get rid of the “cut-off” problem, nor of the requirement to embed a valid tone when you want to use the payload – see detailed explanation below.
The following example depicts the ideal usage scenario of the payload:
As the satellite comes over the horizon, an unmodulated carrier(“quieting”) will be received by all on UHF
Person A starts to transmit on VHF (with valid “transponding”tone embedded in the transmission) and the transmission is relayed on UHF
When Person A releases his/her PTT, the satellite will continueto transmit what it is receiving (usually this will be “noise”) for a further ±3s. Nobody should start to transmit during this time!
At the end of the ±3s period, everybody will again hear theunmodulated carrier.
NB: only when this unmodulated carrier is heard should Person Bstart to transmit. Listen to this mp3 recording as an example of valid usage: http://tinyurl.com/32rjbxm* *
I suppose this will take some getting use to – at least the system has a built-in “punishment” mechanism for the impatient! ;-)
Please refer to previous posts on general voice quality optimization when using the SA-AMSAT payload on SO-67.
I will request Gladys Magagula at the Satellite Application Centre to obtain regular schedules from the regional coordinators as soon as possible. We will start off with day passes only, transmit on 2.5W and see how things go.
Enjoy!
Regards Jan-Albert
*Jan-Albert Koekemoer, PrEng***
*Sun Space & Information Systems (Pty) Ltd.*
Stellenbosch, South Africa
www.sunspace.co.za
+27 21 880 8117 (tel)
+27 83 461 6643 (cell)
+27 21 880 1703 (fax)
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