October 2009 - AMSAT-BB - mailman.amsat.org

Re: requesting help on a RF link solution (imaginary ka-bandlink!)
by i8cvs 28 Oct '09

28 Oct '09

Hi Bob, W7LRD I need to answere your question as well via AMSAT-BB because my emails sent to w7lrd(a)comcast.net are alwais rejected to me by your provider. From the point of view of Amateur Radio the best I can suggest to you is the book " The Satellite Experimenters Handbook " by Martin Davidoff K2UBC 2nd Edition ARRL Order No 3185 ISBN 0-87259-318-5 and also the ARRL " UHF MICROWAVE Experimenters's Manual" ARRL Order No 3126 ISBN 0-87259-312-6 Those books are full of easy calculations and you can follow it using a small scientific hand held calculator but very important every chapter of the UHF MICROWAVE Experimenter's Manual is full of "References and Bibliography " that you can find and read/study to go deeply into details on the above matter covering circuits and antennas which are described here in hardware but also with related easy to follow calculations. At the beginning you must go slowly with the above two books but after a few months you will improve and the above matter will come very familiar to you provided that you implement your knoledge following the recommended References and Bibliography. In AMSAT-BB I follow your experimental activity particularly into the S band.............congrats ! Best 73" de i8CVS Domenico ----- Original Message ----- From: Bob- W7LRD To: i8cvs Sent: Wednesday, October 28, 2009 3:23 AM Subject: Re: [amsat-bb] Re: requesting help on a RF link solution (imaginary ka-bandlink!) Hello Domenico I enjoy your posts, even though many are "out of my pay grade". Would you aim me towards a good tutorial place you may know of where I could learn some of the basics. I would like to gain a better understanding of this concept. Thanks & 73 Bob W7LRD ----- Original Message ----- From: "i8cvs" <domenico.i8cvs(a)tin.it> To: "Samudra Haque" <samudra.haque(a)gmail.com>, "Amsat-bb" <amsat-bb(a)amsat.org> Sent: Tuesday, October 27, 2009 5:44:14 PM GMT -08:00 US/Canada Pacific Subject: [amsat-bb] Re: requesting help on a RF link solution (imaginary ka-bandlink!) ----- Original Message ----- From: "Samudra Haque" <samudra.haque(a)gmail.com> To: "Amsat-bb" <amsat-bb(a)amsat.org> Sent: Tuesday, October 27, 2009 11:03 AM Subject: [amsat-bb] requesting help on a RF link solution (imaginary ka-bandlink!) > 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 2.4x10^9 Hz) > > Question : is 1 gbps not 1x10^9 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 10^9 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 Hi Samudra, N3RDX If I well understand your question is to know what is the maximum free space distance at which you can get a S/N ratio of 4.5 dB using two identical transmitting and receiving systems having the following characteristics: 1) Antenna gain for TX and RX = 56.4 dBi at 32.2 GHz 2) Frequency = 32.2 GHz 3) Overall receiving system noise temperature: T = 3000 kelvin 4) Bandwidth of receiving system = 2.4 x 10^9 Hz 5) TX power 10 W 6) Required Signal to Noise ratio S/N at the unknown distance = 4.5 dB With the above data we first calculate the receiver noise floor Pn = KTB where: K = Boltzmann constant = 1.38 x 10^ -23 (Joule/kelvin) T = Overall System Noise Temperature = 3000 kelvin B = Bandwidth of receiving system = 2.4 x 10^9 Hz Working out the numbers we get the following RX noise floor Pn = (1.38 x 10^ -23) x (3000) x (2.4 x 10^9) = 1 x 10^-10 watt and 10 x [ log (1 x 10^-10)] = - 100 dBW or - 70 dBm 10 Link budged calculation TX power = 10 W =..................+ 40 dBm TX antenna gain ........................+ 56.4 dBi ------------ Transmitted EIRP......................+ 96.4 dBm Free space attenuation for 61.000 km at 32.2 GHz............- 218.3 dB ------------ Received power over isotropic ant. at 61.000 km distance........- 121.9 dBm RX antenna gain.......................+56.4 dB ------------- Received power at RX input... - 65.5 dBm Receiver noise floor.................- 70.0 dBm -------------- Received S/N Ratio................. + 4.5 dB Conclusion: Using two boresight identical parabolic dishes having each a gain of 56.4 dBi at 32.2 GHz one transmitting with 10 watt and the other one receiving with a receiving system having a noise temperature of 3000 kelvin into a bandwidth = 2.4 x 10^9 Hz the free space distance at which the signal is received with a S/N ratio = + 4.5 dB is only 61.000 km so that your hypothetical system is not suitable for the NASA MRO Ka-band experiment because the distance Earth to Mars is about 1 AU i.e. 1 Astronomical Unit corresponding to 149 Million/ km 73" de i8CVS Domenico _______________________________________________ Sent via AMSAT-BB(a)amsat.org. 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Re Which rotator control to use.
by howard dawson 28 Oct '09

28 Oct '09

Hi Eric. I have been using Fodtrack along with F6DQM's (Gabriel Rivat) excellent programme Sat_Explorer for over a year now, with no trouble whatsoever, Fodtrack was home built a long time ago in the days of KO-23, UO22 etc and has never given any trouble. Gabriels programme SAT_Explorer can be downloaded free of charge from his excellent web site http.//www.f6dqm.fr, it is very easy to set up and runs perfectly. Best of luck. 73 Howard G0VBT Amsat 6058 Send instant messages to your online friends http://uk.messenger.yahoo.com

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Diamond Yagis
by John Geiger 28 Oct '09

28 Oct '09

Has anyone tried out the Diamond 2m or 70cm yagis? If so, do they do a pretty good job? They sure are priced nice. I am especially interested in the A430S15 15 element UHF yagi model. 73s John AA5JG

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Nova Satellite Prediction Program
by Jimcknwire＠aol.com 28 Oct '09

28 Oct '09

Installed, reinstalled, changed versions- multiple problems with calculating scripts. What program should I change to?

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PIC rotator control
by Andrew Rich 28 Oct '09

28 Oct '09

Hello I am re-visting a rotator controller. I am curious, should I push the processing of the "compare and make a decision" onto the PIC, or pull that function back into the PC ? PC is LINUX I/O is serial PIC is 16F877 Andrew VK4TEC

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requesting help on a RF link solution (imaginary ka-band link!)
by Samudra Haque 28 Oct '09

28 Oct '09

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 2.4x10^9 Hz) Question : is 1 gbps not 1x10^9 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 10^9 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

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Re: FS items (Arrow, PCR-1000)
by Mark L. Hammond 27 Oct '09

27 Oct '09

The UT-10 L-band module has been sold. Thanks for the interest. The Arrow antenna and the PCR-1000 are still available! 73, Mark N8MH >Date: Mon, 26 Oct 2009 15:51:50 -0400 >Delivered-To: marklhammond(a)gmail.com >Subject: FS items (Arrow, PCR-1000, 1.2 GHz module for TS-790). >From: "Mark L. Hammond" <marklhammond(a)gmail.com> >To: amsat-bb(a)amsat.org > >Hello AMSAT-BB, > >I need to pursue a tower/rotor/antenna project. Therefore, I am >selling some items in the shack to help fund the project. The prices >are "fair" and therefore "firm". I'm giving the BB a shot before I >take these to a local hamfest or eBay. Prices do not include >shipping/insurance. > >1) Arrow II Antenna 146/437-10WBP Satellite version with built-in >diplexer and split boom. Condition: nearly new, only assembled about >5 times. Elements/boom neatly numbered via label-maker tape. $100 + >shipping/insurance. > >2) Icom PCR-1000 receiver. Includes receiver, serial cable, and >power supply. Condition: few minor scuffs/scratches, perfect working >condition. (The variable bandwidth permits reception of 38k4 packet >signals!) $250 + shipping/insurance. > >SOLD 3) UT-10 1.2 GHz L-band module for Kenwood TS-790. This is a >plug-n-play module, about a 5-10 min. no-tuning install. Includes >screws. Condition: Perfect working order, low transmit time, full >10W output. Price: $475 + shipping/insurance. > >Please contact me directly offlist at: marklhammond AT gmail DOT com > > >73, >-- >Mark L. Hammond [N8MH] Mark L. Hammond [N8MH]

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SatPC32, Yaesu FT-736, and KCT
by Jim Bennett 27 Oct '09

27 Oct '09

Has anyone got this configuration working? My current setup is: Yaesu FT-736, WISP, Kansas City Tracker/Tuner with Yaesu 5400 rotor control box. I have try to use Satpc32 with the KCT and it will interface with the rotor control, but will not tune the radio. Do I need a separate cable for the data link? Or will Satpc32 interface with KTC and tune thru the KTC board? Thanks for any info. Jim KE4KOL

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Ares
by rwmcgwier＠gmail.com 27 Oct '09

27 Oct '09

Launch at 9:49 am edt Sent from my Verizon Wireless BlackBerry

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Plan 13 in Python
by Mark VandeWettering 27 Oct '09

27 Oct '09

Bruce's recent experiments with the AVR port of Plan 13 has reminded me that I should make a public release of my Python implementation. I keep thinking that I am going to get to making improvements, but somehow I never seem to get around to do doing it, so rather than just delaying, I'll toss it out in its current state and let people experiment with it. It currently includes a plan 13 module, a module for converting maidenhead grid squares and a couple of example scripts (most notably an "elements" script, for fetching elements, and a "nextpass" script that can be used to find details of the next pass of a satellite, mostly useful for LEO sats, but which illustrate the use of the plan 13 module). Feel free to download and use this code for your own experimentation: it's under an open source license whose only significant feature is to acknowledge Miller's original Plan13 code. The code runs under Python 2.5, and can be found at: http://brainwagon.com/files/pyham-0.1.tar.gz I'd be interested in hearing of any adaptations, extensions or uses of this code. 73 Mark K6HX

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