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Možný problém při Perseidech

(Od: OK1AXH Téma: Krátké zprávy Zveřejněno: 4. 8. 2015)
  • Na Moon-netu proběhlo pár zpráv, které se týkají možného problému při MS spojeních. Za pár dnů jsou tu Perseidy a mohlo by to dost vadit.
    14. let starý amatérský satelit PCSAT (NO-44) má problém, protože se díky poruše přepnul do nouzového režimu a tím spustil svůj maják na 144.390! Takže každý oběh (asi 110 minut) je tento střed random MS pásma v Regionu I. asi na 12 minut zarušen. Stejný kmitočet je ovšem Severoamerická APRS frekvence. Celé, i s dalšími podrobnostmi, to vyústilo do varování IARU_c5, které je v pokračování. (Díky za info Honzo OK1VAO)
Ahoj Petře,
něco na web, je to dlouhé a tak to nepřekládám.
Honza

---------- Původní zpráva ----------
Od: Jacques Verleijen <jacques.verleijen@skynet.be>
Komu: iaru_c5@ml.oevsv.at
Datum: 3. 8. 2015 20:44:55
Předmět: [Iaru_c5] Possible interference due to malfunction of a satellite

Hello all, 

Please release this note to by the channels you have in your society for the
VHF/MS enthusiasts(before the Perseids). 

73 

Jacques ON4AVJ 

 

Possible interference due to malfunction of a satellite 

For the past few weeks many 144MHz meteor scatter enthusiasts have been 
complaining of interference from AFSK packet transmissions. As a 144MHz DX 
enthusiast, in addition to being VHF manager I took an interest and started 
monitoring. 
The transmissions on 144.390MHz FM AFSK occur at regular intervals, mostly 
on Northerly headings from my location near Saxmundham in Suffolk. The 
transmissions fill about 15KHz of spectrum on the waterfall display of my 
SDR receiver. 

 

The impact the satellite signals on narrowband MS users can be seen from 
this video from GM4JJJ 

https://www.youtube.com/watch?v=2ZJgMA4i7PY&feature=youtu.be
(https://www.youtube.com/watch?v=2ZJgMA4i7PY&feature=youtu.be) 

Because of the inclined orbit Northern European amateurs get a longer pass 
than those in the US which means that there is a burst every minute for a 
pass lasting up to about 12 minutes, repeating every 110 minutes orbit time.
Whilst that is not continuous QRM one pass is enough to cause a meteor 
scatter QSO on 144.390 ± 6KHz to fail if they coincide. 

 

Find hereby the text of AMSAT-NA, published in their weekly bulletin: 

 

PCSAT Default Beacon Transmissions on 144.390 MHz 

 

An FM APRS signal has been received in England causing interference to the 
MGM frequency and weak-signal Meteor Scatter (MS) operation which is just 
below 144.390 MHz. A MS DXpedition was disrupted by such activity earlier in
the month and interference has been occurring at various times since. 

 

Bob Bruninga, WB4APR, explains that the beacon was planned over 15 years ago
for operation only when PCSAT is over North America based on published band 
plans at that time. Now, after 14 years on orbit, the ability to turn that 
backup beacon off has been lost. 

 

PCSAT (now 14 years old) had a backup fail-safe beacon on 144.390 that would
activate after any unknown spacecraft reset to give a backup comm link in 
case the primary 145.825 channel died.  Being on the North American APRS 
frequency with hundreds of IGates there would always be at least one that 
would hear this "emergency call home" from PCSAT even though the channel is 
generally saturated.  It worked. 

 

The problem is, that now PCSAT resets on every orbit due to negative power 
budget and so, on every orbit that beacon comes back on.  Even if we did get
a command up to reset it, that setting would last only 15 minutes to the 
next eclipse. 

 

We learned our lesson!  That was our FIRST amateur satellite and we sure 
learned NOT to use a "connected-packet-command link" that needs ACKS and 
Retries and logon passwords  just to LOGON before you can even send a SHUTUP
command.  All our satellites since, operate without the multiple Send, 
connect, ACK, retry, ACK, command, ACK overhead.... just to get one command 
understood.  Now, only the receiver on the spacecraft has to be functional 
to command it to silence in a single packet.  But too late for PCSAT. 
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