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AO-40 passband usage



 Hello All,

Seeing Hilton's message prompted me to jump in with my 2 cents worth of
opinion. In fact, I have been having conversations about this matter with
some others over the last while, both via the  internet and on Ao-40. I may
even be one of the stations that Hilton is referencing in his message, hi.

I operate  using the L-band uplink on Ao-40 as my preferred  transmission
medium and have done so almost exclusively for the last  1 1/2  years.
Therefore, I have always had a keen awareness  of the  conditions  on
L-band, and the numbers of users with L-band capability.

First, it's very apparent to me that the number of  L-band users has gone up
very significantly over the last year, with many of them having the
capability to produce very strong signals. This increase seems to have
occurred in both N. America and in Europe, with my general impression being
that there is a somewhat larger increase in Europe.

What is not clear to me, or others that I talk to, is that this increase in
what are often very strong uplink signals is actually doing harm to other
users of the satellite. I have listened very carefully around the passband
when there are strong L-band stations in operation, and I have yet to see
any evidence that there is a detrimental effect to the other users, be they
on U-band or L-band.  I cannot detect, by ear or signal strength meter, that
other users are having their signal strengths deteriorated when there are
L-band stations operating near,at, or in some cases, over the beacon
strength level.

Watching the beacon telemetry, it is obvious that it takes more than one
very strong L-band  station to begin to even move the L-band agc from it's
nominal position at 1 db, yet the u-band agc is often at the 5-15 db level.
Also, it would seem to me that a very strong  L-band station would need to
start moving the S2 transmitter alc value from it's nominal position before
it began to effect other users, yet I find that the alc very rarely moves,
even when there are a number of strong L-band stations on at the same time.

Now, lest anyone think I'm suggesting that L-band operators  should be
encouraged to operate without regard to the general principles that have
always governed operations on the satellite transponders, that is the
farthest thing from my mind.  I agree that if  everybody operated at beacon
level signal strengths, it would promote a false sense of the receive
capabilities of some of the smaller or newer stations, and as we all know,
you can't have a good quality satellite station without having  better
receive capabilty than transmit capability.

 Also, if  it can be demonstrated that  L-band  operations  that are
stronger than the " beacon level -10 db" value that is suggested for U-band
operations are detrimental, I will be the first to propose that Leila should
be turned on for L-band operations.  I have no concern that I, or  any other
, L-band operator could not manage to still enjoy the satellite if we had to
also contend with Leila on L-band. A level playing field for all does not
scare me in the least.

Comments invited, I have my flame-proof suit at the ready...

regards,

Roy VE7BPB
Vancouver

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