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Re: AO-51 mode V/S



I have gotten good reception using a signal generator with -20dBm 
output on 800-MHz to a simple diode paralleled by a 47-ohm resistor 
mounted in a coffee can placed 20-feet from my dish (my receive 
system is very close to Franscesco's in performance).  I used about 
40-foot of RG-58 for the 800-MHz signal so that dropped the signal 
another 13-dB or so.  The third harmonic would be less than 1/3 the 
power of the 800-MHz signal.

73 Ed - KL7UW

At 05:16 AM 5/14/2008, i8cvs wrote:
>----- Original Message -----
>From: "francesco messineo" <francesco.messineo@gmail.com>
>To: "George Henry" <ka3hsw@earthlink.net>
>Cc: <amsat-bb@AMSAT.Org>
>Sent: Wednesday, May 14, 2008 9:09 AM
>Subject: [amsat-bb] Re: AO-51 mode V/S
>
> > Hello,
> >
> > On 5/13/08, George Henry <ka3hsw@earthlink.net> wrote:
> > > You can use any oscillator module, such as from an old PC motherboard,
>that will put out harmonics up in the 2.4 GHz range.  I happened to find a
>24.000 MHz one on an old MB.  Just now, looking around in the junk drawer, I
>found ones for 4.000 and 16.000 MHz as well.  Add 5 volts and a short piece
>of wire on the output pin, and you're good to go.
> > >
> >
> > I can confirm, I used a 50 MHz xtal oscillator and I have a very
> > strong armonic signal at 2400 MHz.
> >
> > hth
> > 73
> > Francesco IZ8DWF
>
>Hi Francesco, IZ8DWF
>
>To test if your 2400 MHz receiving system is suitable or not to receive a
>satellite signal you don't need a strong armonic signal because  a XTAL
>signal source tell you only 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 has an output power of - 28 dBm measured at 2400.408 MHz
>
>The overall noise figure of my receiving system is 0.7 dB equivalent to
>a noise temperature Te = 51 kelvin
>When the elevation of my 1.2 meters dish is zero degrees the feed get a
>noise level from the ground of about 290 kelvin
>In this condition the equivalent noise temperature Tsys of this receiving
>system  is 51+290 = 341 kelvin and the calculated noise floor with the IF
>receiver switched to SSB in a BW of 2500 Hz is  -139 dBm
>
>With the above sensitivity if I plan to receive with a S/N= + 15 dB my
>- 28 dBm signal source connected to a dipole while  using my 27 dBi dish
>I must put my signal source  in a free line of sight about 20 km away from
>my dish as calculation shows.
>
>Please note that a received signal of + 15 dB over the noise is a very
>good signal for SSB as tell the experience with OSCAR-10, OSCAR-13
>and AO40
>
>Power of  Signal Source ...................   - 28.00 dBm
>
>Gain of  Signal Source dipole...........   +  2.14 dB
>                                                                -------------
>Signal Source EIRP...........................   -  25.86 dBm
>
>Attenuation 2.4 GHz over  20 km.....  - 126.00 dB
>                                                                 ------------
>Power received on isotropic ant......... - 151.86 dBm
>
>Gain of 1.2 m dish.............................. +  27.00  dB
>                                                                  -----------
>Available power at RX input.............. - 124.86 dBm
>
>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
>
>
>
>
>
>
>_______________________________________________
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