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

Re: FO-29



> William Erhardt wrote:
> 
> Howdy Fm Montana - I was calling cq cw on FO-29 on the 23:30 UTC pass
> at 145.950 up and 435.847 down when an FM signal came on freq for
> about 1 minute - I moved up frequency and called again and the FM
> followed me up about 10 kcs and transmiited again. Did anyone else
> here this FM signal
> 
> Bill KA7YAO

Hi Bill,

I have some thoughts about your posting.  The fact that the signal 
"followed" you is proof of "intentional" interference.  When I ask 
myself why anyone would do this, it required me to ponder my long
term experience with the "FO" birds.

First consider this, although I could not find a suggested band plan
for Fuji birds, I trust it is similar to other analog birds.  That
is, voice modes are above the passband center and CW contacts are below
the passband center.  Even a CW signal at 435.847 could be considered
encroaching on the voice segment.  Passband center is 435.850.  

The Fuji birds have very sensitive receivers and a very small uplink
signal is needed for sucessful QSOs' in voice or CW modes. Too strong
an uplink signal stresses the satellite power budget and sucks away the
output power for the rest of the transponder.  For those who have
experienced this phenomenon, you know that this is an insidious form of
interference as usually the offender does not know they are causing a
problem to others.  

The downlink output on the Fuji birds is not very powerful.  Let's 
consider the implications of CW operation on these satellites.  A 
good receiver system is needed to copy the Fuji birds well.  Most 
voice operators use beam antennas with pre-amps.  However, voice 
contacts can be made using egg-beater or verticle antennas, but the 
received signal not near as good.  A very minimal antenna system would
be needed to work CW on these birds, but the operator must always 
make sure the downlink signal is no louder than the beacon.  Any time
the downlink signal is louder than the beacon, it indicates the use of
too much uplink power.  A CW operator needs to be much more carefull
in the adjustment of uplink power levels.  The duty cycle of the CW
signal uses much more of the satellites power budget than the SSB QSOs. 
In other words, it is very easy for CW to cause QRM on these birds.

CW operation is welcome on the Fuji birds and I encourage those that
are interested to try it.  However, if the reason you are using CW is
because you are having trouble hearing the voice conversations on the
Fuji birds, it is likely that what ever power output you use in order
to hear yourself is going to be enough to cause interference to other
operators on the satellite.  If this is your situation, I suggest 
working on upgradeing your receiving system.

Among satellite operators there is a tradition of experimentation and
pride in developing fine receiving systems.  Consider the ZRO awards 
given for copy of weak CW signals through AO-13.

Bill, please don't think I imply that you have caused interference that
provoked retaliation.  I do think it is possible that some individuals
simply do not like CW operators on the Fuji birds because it requires
a very skillfull operator to be courtious in the CW mode.  I certainly
can never justify an individual causing willful interference.  It is
illegal and childish.

Just Food for Thought from N8OCX
Brook Smith


----
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