Hi All,
The specifications of the Arecibo Observatory Amateur Radio Club for the 432 MHz Moon Bounce test on April 16-17 and 18 are as follows:
Dish diameter: 1000 foot equivalent to 305 meters Antenna gain: 60 dBi Tx power: 400 W Tx Frequency: 432.045 MHz
Since the given ERP is 243,902,443 Million Watts (see below) and since 60 dB is equivalent to 1000000 (one Million) time in power it comes out that the power reaching the feed of the dish is:
243902443 / 1000000 = 243 watt
The rest of the power 400-243 = 157 watt is lost in the feed line.
At 432 MHz a dish with a diameter of 305 meters has a -3dB points main lobe angle equal to:
Theta = Lambda / Diameter = 0.69 / 305 = 0.00227 rad.
The above lobe of the dish at an average distance of 380000 km light up a small circular surface S over the moon wich diameter is:
D = 380000 x 0.00227 = 865 km
The surface area S = (3.14 x 865^2) / 4 = 5.88 x 10^11 square meters
All the radiated power of 243 watt by the dish is now collected over the above S area.
The reflectivity of the moon at 432 MHz is the 7% so that the power scattered back isotropically by the moon is ( 243/100 ) x 7 = 17 watt
It is like to say that the power reflected back by the moon is 17 watt feeding an isoptropic antenna or 17 watt EIRP or +12 dBW EIRP radiated isotropically by the moon.
Since the surface of the moon lighed up by the dish is less then the whole surface of the moon the usual calculation procedure for the EME link considering the isotropic attenuation earth-moon-earth cannot be used here because as seen by the Arecibo dish the diameter of the moon is smaller than in reality and is large only 865 km in diameter not 3476 km as is large in reality the moon.
With this is mind we must imagine the dish of Arecibo to be an isotropic antenna with 17 watt applied to it and transmitting all around isotropically from the moon.
My ground antenna has a gain G= 15 dBi and an antenna picked up noise of 70 kelvin when looking at the cold sky
My receiving system at 432 MHz has an overall Noise Figure of 0.7 dB equivalent to 50 kelvin so that the noise floor KTB of my receiving system in SSB with a bandwidth of 2400 Hz is
KTB=1,38 x 10^-23 x (50 + 70) x 2400=3.97x10^-18 watt= -174 dBW
LINK BUDGED CALCULATION:
Isotropic power reflected by the moon...+12 dBW Isotropic attenuation for 380.000 Km.. - 197 dB ------- Power received on isotropic earth ant... - 185 dBW Ground antenna gain...............................+ 15 dBi ------- Power applied to ground receiver..........- 170 dBW Noise floor of ground receiver..............- 174 dBW ------- Received Signal to Noise ratio S/N.......+ 4 dB
By the way when KP4AO will operate on CW I can switch on the 500 Hz filter on my receiver and here I will gain in sensitivity 2400/500 = 4.8 time and 10 log 4.8 = 6.8 dB so that I gain 4 + 6.8 = 10.8 dB of overall 10 Signal to Noise ratio
If I can stake two 70 cm antennas with gain 15 dBi each I can gain about another 3 dB and I can improve the S/N ratio to 10.8 + 3 = 13.8 dB
If I can stack four 70 cm antennas with gain 15 dBi each I can gain about another 3 dB and I can improve the S/N ratio up to 13.8 + 3 = 16.8 dB a real very strong signal on CW or 16.8 - 6.8 = 10 dB in SSB Signal to Noise ratio wich is considered to be optimal for a comfortable reception in SSB
By the way to work EME using a big dish having a lobe with an aperture angle "theta" smaller than the diameter subtended by the moon wich is about 0.5 degrees i.e. 0.0087 radiants is useful only for the big dish to hear better those stations using smaller dishes but the big dish to be received better by the smaller one's "must" use more power and not increase the diameter of the dish because as soon as the moon is completely resolved the power scattered back isotropically do not increase increasing the diameter of the dish.
In conclusion I believe that ground stations with an antenna gain of 15 dBi and a receiving system with an overall Noise Figure of about 1 dB can easily hear KP4AO on CW and barely in the noise on SSB
Stations with the same receiver overall Noise Figure and antenna gain from 18 to 21 dB can hear KP4AO on CW and SSB without problems.
Stations using 100 watt or more and the above antennas ranging from 15 dBi to 21 dBi have chance to make QSO with KP4AO on CW
The above calculation shows that it is very difficult to hear KP4AO or be heard using a small hand-held yagi pointed at the moon.
Have fun
73" de
i8CVS Domenico
----- Original Message ----- From: "MM" [email protected] To: [email protected] Sent: Wednesday, April 07, 2010 3:06 PM Subject: [amsat-bb] Arecibo on 432 MHz Moon Bounce
Hi all: Here is a EME event you cant miss. Dust off your CW key, its time for Satellite, QRP EME.
The 1,000 foot dish has 60 dBi on 432 mc and 400 watts. That comes out to be approximately 243,902,443 Million Watts ERP.
enjoy
wf1f www.marexgm.org
(thanks to KB1MGI for passing on this data)
Arecibo on 432 MHz Moon Bounce
The Arecibo Observatory Amateur Radio Club will be putting the 1000-foot radio telescope on the air for 432 MHz EME from April 16-18.
It can be heard with a small hand-held yagi pointed at the moon
The scheduled times of operation are:
April 16: 1645 - 1930 UTC
April 17: 1740 - 2020 UTC
April 18: 1840 - 2125 UTC
Callsign: KP4AO
Tx Frequency: 432.045 MHz
Rx Frequency: 432.050 to 432.060+
Tx power: 400 W
Antenna gain: 60 dBi
System noise temp: 120 K (cold sky)
System noise temp: 330 K (when pointed at moon)
KP4AO can be heard with a small hand-held yagi pointed at the moon and a good receiver. A 15 dBi antenna and 100 W will be enough to work us on CW.
Operators at KP4AO will do their best to work as many stations as possible. Each session will start with a brief announcement and CQ in SSB. SSB QSOs may continue for 30 minutes to an hour, if the QSO rate remains high.
The mode will be shifted to CW as soon as it is judged that higher QSO rates would result.
We will listen for calls at frequencies 5-15 kHz higher than our own, and even higher if QRM warrants. Callers who s-p-r-e-a-d o-u-t are more likely to be copied.
If you've already worked us in any mode, please do not call again -- give others a chance.
If we call "CQ QRP", we will listen for stations running 100 W or less to a single yagi. Please do not answer such a CQ if you are running more power or have a larger antenna.
On April 18, if we reach a condition where most calling stations have been worked, and we judge that operating in the digital mode JT65B would produce a higher QSO rate, we will switch to JT65B.
Note that any of these planned operating strategies may be changed as circumstances dictate.
We are extremely fortunate to have been granted access to the world's largest radio telescope for this amateur radio good-will event. We look forward to working as many stations as possible in the alloted time!
From QRZ.COM
KB1MGI
Moon-Net Email reflector
http://list- serv.davidv. net/mailman/ ...erv.davidv. net
Moon Bounce information
http://www.vhfdx. info/eme. html
UK Ham makes EME contact with just 25 watts
http://www.southgat earc.org/ news/jan. ..me_contact. htm
Earth-Moon-Earth with 20 Watts
http://www.southgat earc.org/ news/jan. ..h_20_watts. htm
WSJT Software for EME
http://www.physics. princeton. edu/pulsar/ K1JT/
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