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Re: Interference on AO-51



----- Original Message -----
From: "Tim Tuck" <tim.tuck@penrith.net>
To: <amsat-bb@amsat.org>
Sent: Friday, May 05, 2006 1:41 AM
Subject: Re: [amsat-bb] Interference on AO-51


> Robert Bruninga wrote:
> >>>> "Phil Paulhus" <ppaulhus@verizon.net> 05/04/06 10:47 AM >>>
> >> I thing Bob's ideas are right on target.  Using 2 meters
> >> for both the up and down links would open the door ...
> >
> > Ah, but that is the problem.  We cannot have the uplinks
> > and downlinks in the same band.  That is the current
> > problem on ISS.  Because they use 2m for both up and
> > downlinks for school contacts, no other system can
> > use 2m at the same time becuase it will either be
> > jammed when the ARISS system transmits, or it will
> > jam ARISS when it transmits.
>
> Umm... I may be missing something here but cant we use some nice cavities
> or helical filters  just like we do in normal repeaters to reduce or
> eliminate this  problem ?
>
> regards
>
> Tim

Hi Tim VK2XTT

OSCAR III the first radio amateur active real-time communication satellite
lanched 9 march 1965 in a LEO orbit 565/585 miles carried a 50 KHz wide
1 watt transponder that received radio signals near 146 MHz and
retransmitted them,greately amplified, back to earth near 144 MHz thereby
demonstrating that big cavity filters where not needed on board of it and
infact you can see the small size of this satellite reading the book " The
Satellite Experimenter's Handbook " written by Martin Davidoff  K2UBC
Chapter: The Early Days, page 2-11

Probably well designed helical filters were used as you suggested to
sufficiently isolate the upconverter and downconverter only about 2 MHz
apart on this 2 meter in-band transponder in a epoch time 1965 in wich high
dynamic range mixer and transistors were not yet invented and available
and so............imagine the difference in now'adays technology !

Quoting K2UBC,  "OSCAR III operated only 18 days during wich time about
1000 amateurs in 22 countries were heard trough it .A numbar of long
distance communications were reported, including Massachusetts to Germany,
New Jersey to Spain, and New York to Alaska "

Best 73" de

i8CVS Domenico
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