----- Original Message ----- From: "Stefano Simonetti" iw1rdz@yahoo.it To: AMSAT-BB@amsat.org Sent: Sunday, January 20, 2008 5:44 PM Subject: [amsat-bb] mode s converter
Hi to all, I would like to test my "old" AO40 13cm converter
(2400-2402MHz) to see if it is still alive...
I have not any kind of RF generator and I am wondering if some satellite
has now active some tx in that band.
Thanks, 73
IW1RDZ - Steve
Hi Steve, IW1RDZ
You don't mention what type of antenna you are using but if your receiving system was used for AO40 as I remember you must be in condition to actually receive the sun-noise.
Yesterday 19 Jan the solar flux at 2800 MHz was 71 sfu and using my 1.2 meter dish and a preamplifier + downconverter antenna mounted with an overall Noise Figure of 0.7 dB I was able to get a sun-noise with about 4 dB of (S+N) / N well visible on my S-meter.
I live 20 km south of Naples city and if I put my dish with EL= 0° in that direction the noise coming from the Wi-Fi channel-1 is about 20 dB over my noise floor with the antenna pointed for reference at a quite direction in the cold sky usually north with 50 degrees elevation.
A XTAL signal source tell you if you are correctly in frequency but very small in sensitivity of your receiving system because in general the output power of the source is too high and uncalibrated.
My XTAL signal source (G0MRF type) feeding directly a half wave dipole connected to it has an output power of - 28 dBm measured at 2400.408 MHz
The noise floor of my receiving system ( Te = 51 kelvin ) with antenna connected at zero degrees elevation ( Ta = 290 kelvin ) and so Tsys = 341 kelvin is just - 139 dBm with the IF receiver switched to SSB in a BW of 2500 Hz
With the above sensitivity if I plan to receive the beacon with a very strong signal having a S/N of about 15 dB over the noise and using my 1.2 meter dish with a gain of 27 dBi then I must put the beacon in a free line of sight about 20 km away with my dish as calculation shows:
Please note that a received signal 15 dB over the noise is a very good signal for SSB as tell the experience with OSCAR-10, OSCAR-13 and AO40
Measured power of the beacon .. .... - 28.00 dBm
Gain of antenna beacon (dipole) .... + 2.14 dB -------------- Beacon EIRP.................................... - 25.86 dBmW
Attenuation 2.4 GHz at 20 km........ - 126.00 dB -------------- Power received on isotropic ant....... - 151.86 dBmW
Gain of 1.2 m dish....................... ..... + 27.00 dB ------------- Available power at RX input............ - 124.86 dBmW
RX noise floor with ant. connected.. - 139.00 dBm ------------ S/N ratio of received signal............... 14.14 dB
I hope this helps
73" de
i8CVS Domenico