Using my 85cm offset feed dish on 2400-MHz with a 0.6 dBNF preamp (MK232A2), I could see about 1/2 s-unit of sun noise and a similar amount of ground noise when looking at nearby forest on the horizon. Comparing the sun shaddow on the dish vs. noise peak az-el readings would indicate how close the feed was to perfect boresight and alignment.
73, Ed - KL7UW At 06:53 AM 8/13/2009, i8cvs wrote: >Hi Nigel, G8IFF/W8IFF > >You are right > >Aiming the antenna for maximum receiver Sun noise is the best method >because the antenna pattern can be affected by some squint angle and not >be perfectly aligned with the boom but receiving Noise from the Sun in >2 meters and 70 cm implies a very high antenna gain and a very low overall >receiving Noise Figure with a very low Antenna temperature. > >By the way at microwave such as 2400 MHz it is possible to receive the Sun >Noise using a modest dish diameter even when the Sun activity is low as >actually with around 67 sfu at 2800 MHz (10.7 cm) > >See here: > >http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt > >I use this method with my 1.2 meter dish 27 dBi at 2400 MHz and an overall >receiving Noise Figure of 1 dB equivalent to a Noise Temperature of 75 >kelvin > >With the above dish and receiver I actually get a Sun Noise of about 3.5 dB >of (S+N)/N wich is easily readible on the S meter or better using an AC >Voltmeter connected to the audio output of receiver. > >Using a tracking program and aiming the dish for maximum Sun Noise >it is possible to calibrate the AZ and EL angle of the control box for the >through reference Sun position in the sky. > >In addition repeating time to time the above procedure and knowing the >actual Sun's sfu it is possible to monitor the state of healt of our >receiving system. > >By the way without an HEO satellite using 2400 MHz the above procedure >is as well a little and interesting Radioastronomy exercise. > >Best 73" de > >i8CVS Domenico > >----- Original Message ----- >From: "Nigel Gunn G8IFF/W8IFF" <ni...@ngunn.net> >To: "Greg D." <ko6th_g...@hotmail.com> >Cc: <amsat-bb@amsat.org>; <n...@lavabit.com> >Sent: Thursday, August 13, 2009 2:17 PM >Subject: [amsat-bb] Re: rotator questions > > > > How about aiming for maximum receiver noise? That should be even more >accurate. > > > > Greg Wrote: and then adjust the antenna so the shadow falls directly >down the antenna boom. > > _______________________________________________ > > Sent via amsat...@amsat.org. Opinions expressed are those of the author. > > Not an AMSAT-NA member? Join now to support the amateur satellite program! > > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > > > > > >_______________________________________________ >Sent via amsat...@amsat.org. Opinions expressed are those of the author. >Not an AMSAT-NA member? Join now to support the amateur satellite program! >Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
