Hej
Dagens nät på 3740 Khz klockan
10.00
Deltagare
SM0AIG
SM4EFW
SM4JLX
SM6NZV
SM7WSJ
Svåra
konditioner,,,
*ISS synbar i sommarnatten
HO-68
12:45…Turn
On–FM/PACSAT
Europe,NA,South America
13:30…Turn Off
16:00…Turn
On–CW/SSB
India,West Asia,Africa,Europe,NA
16:45…Turn
Off
17:50…Turn On–CW/SSB
India,West
Asia,Africa,Europe,NA
18:35…Turn Off
*SO-67 tillbaka
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:
1. As
the satellite comes over the horizon, an unmodulated carrier
(“quieting”)
will be received by all on UHF
2. Person A starts to transmit on VHF
(with valid “transponding” tone
embedded in the transmission) and the
transmission is relayed on UHF
3. When Person A releases his/her PTT, the
satellite will continue to
transmit what it is receiving (usually this will
be “noise”) for a further
?3s. Nobody should start to transmit during this
time!
4. At the end of the ?3s period, everybody will again hear
the
unmodulated carrier.
5. NB: only when this unmodulated carrier is
heard should Person B
start 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.
En fortsatt god sommar
tillönskas!
73 Håkan SM7WSJ
