[amsat-bb] Re: mode s converter

[i8cvs]

----- Original Message -----
From: "Stefano Simonetti" <iw1rdz at yahoo.it>
To: <AMSAT-BB at 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