[amsat-bb] . Re: International Space Station-Bounce on 1296 MHz

i8cvs domenico.i8cvs at tin.it
Thu May 30 19:54:41 PDT 2013

Von: i8cvs [mailto:domenico.i8cvs at tin.it]
Gesendet: Donnerstag, 30. Mai 2013 01:13
An: Andreas Imse
Betreff: Re: [amsat-bb] Re: International Space Station-Bounce on 1296 MHz
Wichtigkeit: Hoch

Hi Andreas, DJ5AR

Using the RADAR equation I would like to perform a link calculation of your
QSO with Jan PA3FXB through the International Space Station-Bounce on 1296

I already know that the gain of your 3 meter dish is 29 dB and your power at
the feed point is 200 W but I need the additional estimated following

1) The range and the elevation from the ISS and your QTH as soon you started
     receiving your own ECHO'es signals.

2) The maximum range and the elevation from the ISS and your QTH when your
     received signals were the strongest possible.

3) Were you receiving in analogic CW using 500 Hz filter and headphone or
     were you using digital WSJT software such as FSK441 or others software
     (commonly used for rapidly moving meteor scatter QSO's). ?

When the ISS is at the AOS with elevation of 2 degrees the range is about
2000 km and when the elevation is about 35 degrees the range is about 700 km
so that I plan to calculate the budged link for a range 700 km and see what
the results are in Signal to Noise ratio using only a analogic CW receiver
than calculate the advantages using a digital system.

Thanks for your answere.

73" de i8CVS Domenico

----- Original Message -----

From: Andreas Imse
To: domenico.i8cvs at tin.it

Sent: Tuesday, May 28, 2013 9:23 AM

Subject: [amsat-bb] Re: International Space Station-Bounce on 1296 MHz

Hi Domenico,

I saw your posting and will give you a short reply.
We are both using 3 m dishes, 200 W here and 375 W on Jan´s side.

That was far enough for our tests.

As our QTHs are quite close (only 367 km), it is possible that QSOs over a
larger distances might be possible with less power like in aircraft scatter.

If you are equipped for 1296 MHz and able to track the ISS with your
antenna, we should have a try.

Doppler compensation can be done completely on my side.

vy 73,
dj5ar at darc.de

----- Original Message -----
From: "Andreas Imse" <andreas at imse.de>
To: <amsat-bb at amsat.org>
Sent: Thursday, May 30, 2013 10:20 AM
Subject: [amsat-bb] Re: International Space Station-Bounce on 1296 MHz

Hi Domenico and all others, interested in this subj

I am not looking for completing QSOs only and would like to test with
receiving stations too.

if you have an antenna for 1296 MHz and are able to do ISS tracking, we can

I can perform the complete doppler compensation as well for uplink as for
downlink here.

So the receiving station may stay and listen on a fixed frequency ( e.g.
1296,300 MHz).

vy 73,
mailto:dj5ar at darc.de> dj5ar at darc.de

Hello Andreas, DJ5AR / EI8HH

Using the data of your station and that of Jan PA3FXB I was
able to compute the Link Budged calculations for the international
Space Station-Bounce on 1296 MHz


We consider the ISS like a passive reflector with reflectivity
factor of 10 % to try a QSO by reflection Earth-ISS-Earth


1) The solar panels of the ISS plus the central body large like a
     Boeing 747 have a metallic reflecting surface of about
     2000 square meters and we consider the ISS like a circular
     RADAR target having being a metallic plate an estimated
     reflectivity factor S of 10 % at SHF

2) The range EARTH-ISS at elevation of 35 degrees is about
     700 km

3) Our EME station at 1296 MHz uses a 3 meters dish in diameter
     with gain of 29 dB and 200 W at the feed

4) The overall noise figure of our receive system is NF = 0.5 dB
     while the antenna temperature is 50 kelvin when pointed at the
     Cold Sky and we receive on CW using a filter with a BW large
     500 Hz

5) We use only analogic reception without digital software like
     WSJT or similar tecniques.


Aiming the dish towards the ISS when distant 700 km and
transmitting on CW and using the RADAR equation we
calculate the Signal to Noise ratio S/N to see if on CW the
echoes reflected by the ISS are above or belove the Noise
Floor of receiver.

First of all using the RADAR equation we calculate the round
trip attenuation in dB between  EARTH-ISS-EARTH when
approaching to TCA the average range is 700 km

                                 RADAR EQUATION

                                     Pt x Gt x Ar x S
                 Pr =      -----------------------------
                                 ( 4 x 3.14 x R^2 ) ^2

 Where :

 Pr  = power received in watt

 Pt  = power transmitted = 1 watt

 Gt = isotropic gain of a ground antenna at 1296 MHz  = 1 time
          in power or 0 dB

 Ar = aperture area of isotropic antenna at 1296 MHz = 0,0043
          square meters

 S = Sigma or Radar Cross Section i.e. the surface of the ISS in
        square meters with reflecting coefficient of 0.10 = 10 %

 R = distance or range EARTH-ISS = 700 km = 700000 meters

 (4 x 3.14 x R^2)^2  calculates the surface of a sphere having a
 radius R=700000 meters elevated time 2 to take account of the
 round trip  "EARTH-ISS-EARTH"


S = Sigma of the ISS with reflecting surface of 2000 square meters
and reflection coefficient of 10 % = 2000 x 0.10 = 200 square meters

Calculation of the aperture area  Ar of isotropic antenna at 1296 MHz

                / 2                      2
              /\              0,2314
Ar = ---------- =  ----------- = 0,0043  square meters
         4 x 3,14       4 x 3,14

Calculation of the received power Pr on the EARTH
collected by the isotropic antenna at 1296 MHz

              1 x 1 x 0.0043 x 200                         -26
Pr = --------------------------------- = 2.27 x 10      watt
         (4 x 3.14 x 700000^2 )^2

Calculation of the attenuation Att for the Round-Trip

                 Pt (1watt)
 Att =  ---------------------  = 4.41 x 10       time in power
            2.27 x 10    watt

and in dB the Att = 10 log    4.41 x 10     =  256.4 dB


Data of the 1296 MHz receiving system :

Overall Noise Figure of receiving system NF= 0.5 dB = 35 kelvin
Bandwidth BW of receiver on CW  = 500 Hz
Equivalent Noise Temperature Ta of the antenna when aimed toward
the Cold Sky = 50 kelvin

Calculation to get the Noise Floor KTB of receiver

Where :
K = Boltzmann constant = 1,38 x 10      joule/kelvin

T = Equivalent noise temperature Ta of the antenna  plus the
equivalent Noise Temperature Te of receiver i.e. T= (Ta + Te)

Computation of the overall Noise Factor F for the receiver
F = 10 ^ (NF/10) and so F = 10 ^(0,5 / 10) = 10 ^0,05 = 1,12
in factor

The equivalent overall Noise Temperature Te of the receiver is
Te = ( F-1) x 290 = (1,12 -1) x 290 = 35 kelvin

The overall Noise Floor KTB of the receiving system with the
antenna connected is :

KTB = K  x  ( Te + Ta ) x BW  and in numbars :

 Noise Floor KTB = 1,38 x 10    x  ( 35 + 50 ) x 500 = -182.3 dBW

on CW

TX power at feed.................................+23 dBW = 200 watt
Antenna Gain in TX................. ...........+29 dBi
EIRP transmitted to the ISS. ..............+52 dBW  = 158.5 kW
Attenuation  EARTH-ISS-EARTH... - 256.4 dB
Power Pr received on EARTH  over
isotropic antenna   ............................ - 204.4 dBW
Antenna Gain in RX.........................  +  29 dB
Power incident at receiver input ...... - 175.4 dBW
RX Noise Floor......................... ........- 182.3 dBW
S/N ratio CW at RX audio output...  +  6.9  dB


At a range of 700 km from the ISS and using a 3 meters dish with
200 W at the feed and a receiving system with a Noise Floor of
-183.3 dBW = - 153.3 dBm it is possible to hear your hown echo
signals in plain analogic CW with a Signal to Noise ratio S/N of
+6.9 dB wich is very strong.

If two stations are equipped with the same equipments it is
possible to make good QSO for a short time when the ISS
is close range around 700 km at elevation of about 35

Increasing the BW of receiver at 2700 Hz to try receive SSB
it is very difficult since the signal reflected back by the ISS
will be very noisy with a S/N ratio of about - 0.5 dB and so
belove the Noise Floor of your receiver.

It is necessary to use a precise traking system particularly fast
to move the dish as soon the ISS approach the TCA because
the beam wide of a 3 meter dish with gain of 29 dB is large
only about 5 degrees at the -3 dB points so that traking the
ISS at 1296 MHz with a 3 meter dish or even larger for EME
it seems to be the more critical point.

73" de

i8CVS Domenico

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