Von: i8cvs [mailto:[email protected]] 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 MHz
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 informations:
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 and than calculate the advantages using a digital system.
Thanks for your answere.
73" de i8CVS Domenico
----- Original Message -----
From: Andreas Imse To: [email protected]
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, Andreas DJ5AR / EI8HH [email protected] www.dj5ar.de
----- Original Message ----- From: "Andreas Imse" [email protected] To: [email protected] 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 try.
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, Andreas DJ5AR / EI8HH mailto:[email protected]> [email protected]
-------------------------------------------------------------------------- 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
LINK BUDGED CALCULATIONS by i8CVS
We consider the ISS like a passive reflector with reflectivity factor of 10 % to try a QSO by reflection Earth-ISS-Earth
DATA:
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.
CALCULATION PROCEDURE :
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
NOTE: (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"
CALCULATION OF ATTENUATION "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 EARTH-ISS-EARTH
Pt (1watt) 25 Att = --------------------- = 4.41 x 10 time in power -26 2.27 x 10 watt
25 and in dB the Att = 10 log 4.41 x 10 = 256.4 dB 10
CALCULATION OF THE OVERALL NOISE FLOOR FOR THE RECEIVER :
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 : -23 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 :
-23 Noise Floor KTB = 1,38 x 10 x ( 35 + 50 ) x 500 = -182.3 dBW
LINK CALCULATION "round trip" EARTH -ISS-EARTH at 1296 MHz 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
CONCLUSION :
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 degrees.
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