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

ao-40 s -ant pattern, -eirp estimate -some data -rotation measured



Its kind of nice to know the AO40 s band is on all the time to be able to
measure its pattern,
took the time to set up a precise frequency cal, and set up a siggen
harmonic sent out to the dish,
  to cal out the freq errors.
Learned how to put bahn latitudes into winorbit and am able to better
understand why there
are times I couldnt find the satellite and what the squint was at that time.
To summarize:
Very confused at first why I could hear it fine sometimes and just never
find it other times.

*2401.323 non doppler.
*AO40 has a pretty teenie signal off the sides and zippo off the back. Not
too bad in the front cone.
*You have to know the squint angle. Have to use 80 not 270 like the man
says.
*impossible to find if squint is >120 and range is 60,000km.
Studied pictures of the satellite to figure out what hardware was around the
antenna that
might cause this pattern. I think as long as

*Have yet to look at it when it is supposedly pointed squint angle 0. eirp
unknown.
  If I take the signal I get off the side and put that to the main beam of
the satellite S dish its 31db s/n and in
wideband 150khz its still 18db snr. If I stay at 2.5k bw and knock down the
antenna,
to a 17db feedhorn, it still has 12.3db s/n. Thats just with a feedpoint
signal equal
to the peak of what I get now. Should be pretty strong if it ever gets
pointed this way.

*The pattern from squint 20 to 50 degrees squint is usable here for some
data but due to the
11.509 rotation and a few nulls in the pattern, a data block size of 512
40bits/sec thats 12.8 seconds,
  has 3 dead spots punched in it. EIRP 0.1w
P3d locks well but always fails CRC, garbles but readable if one ads
multiple frames together.

Maybe if it repeated the same block several times they could be added
together or change the format
to FEC or shorter blocks with CRC. Got a fair bit of capture but again it
has 20% hole punched into it.
The software just wasnt designed for this kind of data puncturing.
At S band it takes amazingly small amounts of power to make a link though.

*The pattern from squint 80 to 100 is two peaks for about 10% of the
rotation and in the noise the other 80%.
P3D occasionally locks and shows short blocks of text. eirp .05w peak

*The pattern from 120 to 180 can be detected only at low altitudes but has
more fill to it then the squint90.


1/3/2001 and 20 degrees to 45 degrees,
Able to capture 70% of the bits but Block length of 12.8 seconds ??? < am I
right here > is a bit long
for this rotation rate.
1/4/2001: Locked in with squints from 85-95 degrees.
Measure a rotation rate of 11.509 RPM.
Measure Az El while tracking - maches set 19 within 2 degrees.
Usable data +4db above noise period 1 second out of the 5 .21 period
remainder in noise 2 peaks at squint96.
Use a frequency of 2401.323.
Pattern at squint 96' 2 peaks on the s antenna side with 3 or 4 little
ripples.
Every once in awhile p3d sees the sync and captures mostly garbage...
The blocks need to be much shorter to get CRC to work but perhaps some
clever software designed around the
rotation rate and antenna pattern could recover some data.
Still it synced up on 3 blocks or so. Very little readable, maybe a few
words at a time.

Did the seti link budget spreadsheet on this satellite and the tdrss. There
was one floating around
in amsat on a web page but I think it opened in the browser and I didnt save
it.

In the seti sheet units are light years, remeber if you use this put range
in light years then check the meters figure
Can someone tell me what the actual tx power is? Pretty pathetic signal off
the side and back of this sat, but
could be usable.  I am telling you here what I think the eirp is. 6 foot
dish minimum it looks like to me
off the side of it as things are now.


http://www.setileague.org/software/spreadsh.htm

This is at squint 90 and applies to the peak value.

The SETI League, Inc.   Link Analysis
User specifies variables shown in  Bold

Transmitter:
Frequency  = 2401.323 MHz;   l  =   12.5 cm
Transmit Power  = 8.0E-02 W   = -11.0 dBW  =   19.0 dBm
Eff. antenna diam.  = 0.06 meters   = 0   ft
Illum. Efficiency  = 25 %
  Computed Antenna Gain = 5.7E-01 Ap  = -2.4 dBi
  Antenna Half Power Beamwidth = 2.1E+00 radian  =   1.2E+02 degrees
  Effective Isotropic Radiated Pwr  = 4.6E-02 W  =   16.6 dBm

Path:
Range  = 1.95E-09 parsecs = 6.357E-09 LY  =   6.0E+07 m
  Free Space Isotropic Path Loss  =   195.6 dB
  Incident Isotropic Power =  EIRP -  path loss  =  -179.1 dBm

Receiver:
Eff. antenna diam.  = 2.76 meters   = 9.0551 ft
Illum. Efficiency  = 75 %
  Computed Antenna Gain = 3.6E+03 Ap  = 35.6 dBi
  Antenna Half Power Beamwidth = 4.7E-02 radian  =   2.7E+00 degrees
  Drift Scan time (zero declination) = 1.1E+01 min  =   640.5 sec
  Recovered Power =   P inc + G ant  =   -143.5 dBm
  System Noise Temperature = 50 K   =   -7.6 dB/To
  Detector Noise Bandwidth = 2500 Hz  =   34.0 dB/Hz
  Receiver Noise Threshold  =   kTB  = 1.725E-18 J/S  =   -147.6 dBm
  Integration Time = 4.00E-04 sec  =   0.0 dB/cy

SIGNAL TO NOISE RATIO     4.2 dB

This is the best I think I've seen here...... squint 30 at lower range.

The SETI League, Inc.   Link Analysis
User specifies variables shown in  Bold

Transmitter:
Frequency  = 2401.323 MHz;   l  =   12.5 cm
Transmit Power  = 2.0E-02 W   = -17.0 dBW  =   13.0 dBm
Eff. antenna diam.  = 0.06 meters   = 0   ft
Illum. Efficiency  = 30 %
  Computed Antenna Gain = 6.8E-01 Ap  = -1.7 dBi
  Antenna Half Power Beamwidth = 2.1E+00 radian  =   1.2E+02 degrees
  Effective Isotropic Radiated Pwr  = 1.4E-02 W  =   11.4 dBm

Path:
Range  = 6.00E-10 parsecs = 1.956E-09 LY  =   1.9E+07 m
  Free Space Isotropic Path Loss  =   185.4 dB
  Incident Isotropic Power =  EIRP -  path loss  =  -174.0 dBm

Receiver:
Eff. antenna diam.  = 2.76 meters   = 9.0551 ft
Illum. Efficiency  = 75 %
  Computed Antenna Gain = 3.6E+03 Ap  = 35.6 dBi
  Antenna Half Power Beamwidth = 4.7E-02 radian  =   2.7E+00 degrees
  Drift Scan time (zero declination) = 1.1E+01 min  =   640.5 sec
  Recovered Power =   P inc + G ant  =   -138.5 dBm
  System Noise Temperature = 50 K   =   -7.6 dB/To
  Detector Noise Bandwidth = 2500 Hz  =   34.0 dB/Hz
  Receiver Noise Threshold  =   kTB  = 1.725E-18 J/S  =   -147.6 dBm
  Integration Time = 4.00E-04 sec  =   0.0 dB/cy

SIGNAL TO NOISE RATIO     9.2 dB




----
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