Hi Samundra, don't see which path loss you assumed, but for 1 AU (149 mill km), I calculate 286 dB @32 GHz.
Also 3000K seems much to bad.. assume 300K. So let's add up for 1 AU: 40 dBm (10W) +2x56.4 dBi -286 = -133.2 dBm at RX input 1 Gbit/s assumes 1 GHz bandwidth. 300K is roughly -174 dBm/Hz. 1 GHz = 60dB worse = -116 dBm. So you end up with -133.2 - (-116) = -17.4 Eb/No.. not good. If you add 20dB you end up at 2.6 dB Eb/No. Not brilliant, but close. 20dB means 0.1 AU instead of 1 AU = 14.9 Mill km. I think your result was 4.6E9 m (!), not km.. which is 4.6 mill km. Should be it, if getting back to your assumed 3000K RX. 73s Achim, DH2VA > Date: Tue, 27 Oct 2009 06:03:30 -0400 > From: Samudra Haque <samudra.ha...@gmail.com> > Subject: [amsat-bb] requesting help on a RF link solution (imaginary > ka-band link!) > To: Amsat-bb <amsat-bb@amsat.org> > Message-ID: > <d8c724880910270303k9a3b9cch123289eebcaeb...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Hi, amsat-bb > > CQ any satellite link budget expert ! > > I'm trying to do a calculation on my own based upon published specs > for the NASA MRO Ka-band experiment, but am getting some unexpected > results for a Ka-band simplex link with Temp=3000K (hypothetical), > operating with a Signal to Noise ratio (unitless) figure of 1.171 > (representing 4.5 dB eb/no with a data rate of 1 Gbps and a bandwidth > of 2.4x109 Hz) > > Question : is 1 gbps not 1x109 bps ? > > Question : if both antennas are 3m parabolic (both are the same type) > with 56.4 dBi boresight gain, what would you think the furthest > distance the link can perform with SNR of 1.171. I have actually used > a padding of 3 dB Eb/No in my link budget, so am not worried about any > further signal loss at first (ok, I should be ..) For the exercise, I > am choosing a 10 Watt estimated output on an arbitrary basis. > > So: > > P_t = 10W > > G_t = 56.4 dBi = G_r , can we assume the same gain for TX and RX on a > parabolic dish ? > > T = 3000K at receiver > > SNR = 1.171 required > > f=32.2 GHz > > B = 2.4E9 Hz, (bpsk, ldpc code 0.5) > > DR = 1E9 bps > > So, I am puzzled why this link budget says the range with these > parameters is equal to 4.644 x 109 Km -- that seems to be a long > distance ! What am I not able to conceptualize. > > > BTW, I know if I send this out, the answer will come to me soon > thereafter, but for education, I would like to know where the problem > in my understanding lies ! > > > Samudra N3RDX > > > ------------------------------ _______________________________________________ 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
