On Jan 20, 2008 12:44 PM, Stefano Simonetti iw1rdz@yahoo.it wrote:

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

Steve:

I don't believe there is a permanent S-band signal in LEO that makes an easy means of testing your downconverter. The CanX-2 cubesat will have a downlink in s-band, but some modulation modes are less useful for setting up a system than others, and I can't tell what modulation they'll be using, or on what frequency, exactly.

I guess we might have S-band from the ISS some time soon, too.

If you need a cheap-and-dirty signal source, try using one of those small, canned RF oscillators at 40 MHz. Properly powered with a 5v voltage regulator and a 9v battery, it will produce a harmonic signal that you'll hear well from right next to the downconverter, and, with a gain antenna, from some distance away. Don't worry about building it an antenna. If you're not sure if what you're hearing is the sig gen. or a birdie, just blow on the sig gen, and its frequency will warp!

At $2, it was all I used to hack and tweak my downconverter. I got this idea from a VE2 ham's webpages, but I can't seem to google them up right now.

----- 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