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Re: SQUINT vs Performance Profile from AO-40



Dear OM,
The information posted was tabulated using  Bit Error Analysis.
Every telemetry block downloaded has been analysed using criteria to
establish, error free (CRC'd ) useable non-error free and unusable
non-error free blocks. The error free bits are referenced to the useable
non-error free bits to establish the performance profile.
The performance profile encompasses as a whole the variables which
include spin modulation, shielding of the S2 helix by other aerials on the
platform, variable range, "black holes from trees", etc etc.
I have conveniently lumped them all together to define a performance
profile.
The partial shielding of the S2 helix is an interesting phenomena to watch
on the S meter. It is most noticeable at the lower squint angles and has
been measured at 8 to 10 dB . The cyclic variance can be timed with a
 stop watch to establish the spin. At low squint angles it does not impact
on the downlink performance, but becomes a contributing factor of bit errors
once the squint is greater than 25 degrees. The total result is a complex
mix
of all the above, possibly others I have not contemplated.
On the subject of EiRP etc I am not adequately versed technically to
offer an opinion.
Best regards,
Colin VK5HI

----- Original Message -----
From: "nn0v" <nn0v@home.com>
To: "Colin Hurst" <hurst_cj@msn.com.au>; <amsat-bb@AMSAT.Org>
Sent: Tuesday, July 17, 2001 5:24 AM
Subject: Re: [amsat-bb] SQUINT vs Performance Profile from AO-40


> How do you take into account the rotation mod that seems to hit at about
30
> degrees offpoint?
> Are these measured db or by signal to noise?
>
> I just finished tracking it at el 15 degrees to the east squint 90, had
10db
> or more ripple,
> could not connect to goddard, I dont think that works anymore.
>
> The ao40rcv was displaying many good pieces of telemetry if I watch it for
> awhile I get some readings
> I can beleive, just as long as that data chunk wasnt in one of these
nulls.
> Cant figure out the EIRP here,
> too much dish shading at that low elevation, but I recorded some maximums
at
> some other passes,
>  do you come up with 8 watts or so for the EIRP?
>
> Anyone in USA the 7/18/2001 pass is a good one should be worth a try, at
> 23:30z
>
>
> > VK5HI S2 Downlink Performance Profile
> > Squint    dB
> > 0           0.0
> > 5           0.0
> > 10         0.0
> > 15       -0.5
> > 20       -1.5
> > 25       -3.5
> > 30       -6.0
> > 35       -12.0
> > 40       -24.0
> > 45       -30.0
> > 50       -27.0
> > 55       -22.0
> > 60       -16.0
> > 65       -16.0
> > 70       -22.0
> > 75       -29.0
> > 80       -35.0
> > 85       -38.0
> > 90       -40.0
> >
>
> ----
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