[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: AO-40 sounded great on Sunday



Howard

I would like to echo your comments regarding the current attitude being 
wonderful for simple systems.

I was receiving 100% CRC good tlm blocks on Sunday morning with an indoor 9 
turn helix pointing through a (closed) window, and 0.8dB NF 
downconverter.  This system is marginal for solid tlm at apogee, and it 
shows just how good things are at the moment.  Unfortunately many stations 
seem to be under the impression that AO-40 is shut down until April - far 
from it.  Also, the short "low" squint slot encourages everyone to come on 
giving good concentrated activity "sessions".

At these squint angles, it is interesting to note the different fading 
characteristics of the downlink signals.  With the squint around 20-25 
degrees,  using a CP receiving system, the beacon level has barely 
noticeable spin fading.  Likewise both linear and CP uplinks on 1269 have 
little fading.  435MHz linearly polarised uplinks seem to suffer the most, 
while CP seems to be OK.

It is a shame, though, that at least one station is taking advantage of 
the  "better" characteristics of the Mode-L uplink by running so much erp 
that he was consistently as loud as the MB, while demonstrating on air that 
he could not get such a good downlink with Mode U, as  Leila kept biting.

Perhaps it is time for the command stations to remind us again of good 
operating practice!

73

Charlie



At 10:16 21/01/02 +0000, Howard Long wrote:
>Folks,
>
>I had some really easy QSO's from the UK into Europe and North America on
>AO-40 on Sunday 20 January 2002 between 10:15 and 11:20 GMT when the bird
>was just restarting its new orbit. South America was in view too but there's
>not much activity from there.
>
>Time (GMT)      MA      Squint   Range (km)
>10:15            9        39       12,700
>10:45           15        22       19,200
>11:15           22        22       25,300
>
>So despite the appalling squint, this was offset by the close range of the
>bird. There was also some QSB which occurs at larger squints: either due to
>polarisation mismatch or because the motor nozzle gets in the way at higher
>squints [assuming there's still a nozzle there ;-) ].
>
>Similar conditions occur with AO-40 every four days, but 25 minutes earlier.
>For instance on 24 January 2002, at 09:50 or so the same conditions will
>occur, assuming the spacecraft's ALON/ALAT has not changed significantly.
>
>Catch the bird early in the orbit between MA's 9 and 30 and you should
>certainly have no problem hearing it, and you should be able to work it too
>even with the current ALON/ALAT of 300/-8!
>
>Indeed, this situation is extremely reminiscent of our QSO parties back in
>May 2001 when the transponder was first switched on and many of us were
>using helices and not dishes. At one point on Sunday as an experiment I
>pointed a 6" long 7 element yagi in the general direction of the window and
>was picking up Q5 SSB QSO's at a range of 17,000km.
>
>Of course, the timing of these conditions will vary widely depending on your
>location.
>
>73 Howard G6LVB
>
>----
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home