Ham Satellite news

PCSAT Default Beacon Transmissions 144.390 MHz

Det har visat sig att PcSat skickar ut beacon på 144.390 MHz vilket Bob Bruninga, WB4APR, förklarar varför här:
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 144.39 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

We are sorry that we have no good answers.  But we hope we can mitigate
this instance of “friendly fire” collateral damage so that we don’t cause
an overall black-eye to amateur radio overall friendly operations?

What you may hear will be 2 one-second packets per minute, one at 1200
baud and one at 9600 baud, trying to “call home”.

[ANS thanks Bob, WB4APR, for the above information]


Webmaster and member of the AMSAT-SM steering group.

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