[amsat-bb] APRS signal "W3ADO-1" being heard in the UK

[Robert Bruninga]

We need to be careful not to blame PCSAT (which identifies itself in each
of its occasional 1 second packets) for every unknown signal heard on
144.39 in the UK.  Maybe someone could record the unknown interference
being heard so we can be sure to separate the known few PCSAT packets from
all the other possible sources of weak emissions that could possibly be
heard by sensitive receivers…



Then we will know what is and what is not emitted from PCSAT.



Thanks

Bob, WB4APR





*From:* M5AKA [mailto:m5aka at yahoo.co.uk]
*Sent:* Thursday, July 30, 2015 3:34 PM
*To:* Robert Bruninga; AMSAT BB
*Subject:* Re: [amsat-bb] APRS signal "W3ADO-1" interfering with Meteor
Scatter in England



Thank you for explanation Bob.



The MS community in Europe has been suffering this interference for several
weeks. I have not seen any notifications on this list that there was a
problem with NO-44.



When did you first become aware of the problem ?



> We learned our lesson!  That was our FIRST amateur satellite and we sure

> learned NOT to use a "connected-packet-command link"



May I suggest that the lesson to be learned is NOT to use frequencies like
144.390 MHz which have not been agreed Internationally for satellite use
across all three IARU Regions.



73 Trevor M5AKA







On Thursday, 30 July 2015, 20:08, Robert Bruninga <bruninga at usna.edu> wrote:



> An FM APRS signal has been received in England on 144.390 MHz.
> Does anyone know if 144.390 APRS is installed on any current orbiting
satellite...

So sorry, but yes.  "Houston, we have a small problem..."  I hate to say
it, but that beacon was IARU coordinated 15 years ago for operation only
when PCSAT is over North America, but after 14 years on orbit, we have
lost the ability to turn that backup beacon off.

PCSAT (now 14 years old) had a backup fail-safe beacon on 144.39 that
would activate after any unknown spacecraft reset to give us 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.  And 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.

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".

Bob, WB4APR
Naval Academy
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