July 2007 - AMSAT-BB - mailman.amsat.org

Re: Future radical satellite designs
by Fred A Parker 09 Jul '07

09 Jul '07

I am in the process of putting a group together of local amateurs to build and launch a triple Cubesat. The club will be called the Northern Lakes Amateur Satellite Organization. we have already drawn up the bylaws and a locale ham, an attorney is preparing the paper work. The website should be up in about two weeks. Our goals are to put together a single ham radio payload in a cubebesat. Have spoken to several persons in the Amsat NA origination. They have agreed to do the peer review for us. As we are week in electronics part of it. I am a retired aerospace machinist and have for the last three years been doing a lot of the mechanical work for Amsat. So the mechanical side of it will be easy for us. On the payload we have not made a final decision. Here is some of our ideas. 1: Leverage from the electronic package that is planned for Suitsat 2. This our preferred payload. As it would give us a lot of flexibility with the SDR transponder. Only problem is when is suitsat 2 going to be ready? If it is going to take to long our group may not want to wait. 2: Would be to build a transponder with hamtronics kits. Upside of this is that all parts are off the shelf and could be easily assembled in few months. Bob Bruninga has been using them for some time with success. 3: Ask someone to build us a transponder who has more experience than us. On the orbit. To me the ideal orbit would be an MEO orbit. To see what that would mean I suggest David's G0MRF http://www.g0mrf.freeserve.co.uk/MEOSAT.htm website I have seen some talk on the web that that SpaceX maybe launching cubesats into MEO. Otherwise there seems to be launch availability in LEO. Fred KF0AK

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1.2 GHz antennas
by John Kopala 09 Jul '07

09 Jul '07

Any recommendations for 1.2 GHz satellite antennas? I've been looking at a Directive Systems 2325LY as a possible choice. I was trying to find an antenna of similar size with circular polarization switchable between RHCP and LHCP. John Kopala N7JK

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hi-gain antennas
by Fernandez Montaña, Juan Antonio 09 Jul '07

09 Jul '07

Hi Joe, I have been using these antennas for years and I did not have any problem. One of the main advantages is that they are not very heavy. You can see a comparative of CP antennas at http://eb4dka.tk , into the "archivos" carpet there are several articles in relation satellites apart form the comparative. The articles are in Spanish although you will not have any problem to understand the tables. Surely at the end of the summer the Web will be in English too. Juan Antonio EA4CYQ 73s =============================================================== Este mensaje se dirige exclusivamente a su destinatario. Los datos incluidos en el presente correo son confidenciales y sometidos a secreto profesional, especialmente en lo que respecta a los datos personales, se prohibe divulgarlos, en virtud de las leyes vigentes. Si usted no lo es y lo ha recibido por error o tiene conocimiento del mismo por cualquier motivo, le rogamos que nos lo comunique por este medio y proceda a destruirlo o borrarlo, y que en todo caso se abstenga de utilizar, reproducir, alterar, archivar o comunicar a terceros el presente mensaje y ficheros anexos, todo ello bajo pena de incurrir en responsabilidades legales. Cualquier idea contenida en este correo es exclusiva de su autor y no representa necesariamente el criterio de Iberdrola. El emisor no garantiza la integridad, rapidez o seguridad del presente correo, ni se responsabiliza de posibles perjuicios derivados de la captura, incorporaciones de virus o cualesquiera otras manipulaciones efectuadas por terceros. This message is intended for the exclusive attention of the address(es) indicated. Any information contained herein is strictly confidential and privileged, especially as regards personal data, which must not be disclosed, in accordance with legislation currently in force. If you are not the intended recipient and have received it by mistake or learn about it in any other way, please notify us by return e-mail and delete this message from your computer system. Any unauthorised use, reproduction, alteration, filing or sending of this message and/or any attached files to third parties may lead to legal proceedings being taken. Any opinion expressed herein is solely that of the author(s) and does not necessarily represent the opinion of Iberdrola. The sender does not guarantee the integrity, speed or safety of this message, not accept responsibility for any possible damage arising from the interception, incorporation of virus or any other manipulation carried out by third parties. ===============================================================

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Re: Hy-Gain Yagi Antenna
by Pughkeithd＠cs.com 09 Jul '07

09 Jul '07

In a message dated 7/8/2007 10:40:06 PM Central Daylight Time, gary_mayfield(a)hotmail.com writes: > Subj: [amsat-bb] Hy-Gain Yagi Antenna > Date:7/8/2007 10:40:06 PM Central Daylight Time > From:gary_mayfield@hotmail.com > To:amsat-bb@amsat.org > Received from Internet: > > > Is anyone using these antennas? > > Hy-Gain http://www.hy-gain.com/ > UB-7030SAT > VB-216SAT > > What do you think of them? > > 73, > Joe kk0sd > Amsat 21357 > > _______________________________________________ > Sent via AMSAT-BB(a)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 > Joe, I have used a set of these as portable antennas for many years. The first use was for W1AW/5 the first year (1989?) we hosted the ARRL National at Ham-Com. Initial assembly was a challenge but we made it. The longest use was at the Soviet Space Exhibit in Fort Worth (1991). They were installed on top of the exhibit hall for six months and were used daily for LEOs and AO-13. They have been used for every Field Day since initial purchase and for several ARISS School Contacts (2 m only). I worked you with them on a couple of Birds this Field Day. I have used them on my portable tripod in my own back yard for several extended periods. Performance has always been good and they have withstood the partial disassembly and transportation well. The disassembly was only to shorten the booms. Elements were left in place. One of these days I will finally get around to replacing my KLMs (they have not been functional for some time) at the home QTH and the Hy-Gains will be considered along with the M2 antennas. I hope this helps. 73 - Keith, W5IU

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Field Day 2007
by Bruce 09 Jul '07

09 Jul '07

Now that field day is over, I hope everyone that participated had as much fun as they had expected. There is just one more thing to do. Be sure to send in your results and photos. If you are going to send via email (the preferred method), I will confirm that I have received your email (give me a day or two). If you do not get the confirmation, then something happened and you should resubmit. The deadline for receiving your submission (either email or postal mail) for AMSAT Field Day is Monday, July 16, 2007 at 11:59 P.M. CDT. 73...bruce -- Bruce Paige, KK5DO AMSAT Director Contests and Awards ARRL Awards Manager (WAS, 5BWAS, VUCC), VE Houston AMSAT Net - Wed 0100z on W0KIE Intelsat Americas, T1, 6.2/6.8Mhz Also streaming MP3 at http://www.amsatnet.com Latest satellite news on the ARRL Audio News http://www.arrl.org

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Re: Fwd: Future radical satellite designs
by Patrick McGrane 09 Jul '07

09 Jul '07

Hello maggie- I hate it when people snip or take things out of context. Go back to the original entire email to absorb the reason. thanks, patrick ------- Original Message ------- >From : Margaret Leber[mailto:maggie@voicenet.com] Sent : 7/8/2007 8:27:59 AM To : amsat-bb(a)amsat.org Cc : Subject : RE: [amsat-bb] Fwd: Future radical satellite designs On 7/8/07, Patrick McGrane <N2OEQ(a)aceweb.com> wrote: > Some will argue that they want continuous duty whenever the satellite is in range, day or night. > I would like to see a longer lived satellite capable of full power half the time that could > potentially last several decades in orbit. That's really insightful. So many of the birds end up operating in that mode *anyway*; what could be accomplished if we designed them that way on purpose? -- 73 de Maggie K3XS Editor, Phil-Mont Mobile Radio Club Blurb - http://www.phil-mont.org Elecraft K2 #1641 -- AOPA 925383 -- ARRL 39280 By the way, inbound email is broken on the address you're using: "SMTP Error (state 13): 550 5.1.1 <Patrick.McGrane(a)aceweb.com> is not a valid mailbox" _______________________________________________ Sent via AMSAT-BB(a)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

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Re: Future radical satellite designs
by G0MRF＠aol.com 09 Jul '07

09 Jul '07

In a message dated 08/07/2007 17:06:50 GMT Standard Time, N2OEQ(a)aceweb.com writes: I did read the whole thing. The challenges to amateur secondary payloads on commercial or military spacecraft have been discussed here at length in the past. *My* comment was that a standalone bird *designed* without battery-powered transmitters might be an interesting approach. Hello Patrick / Maggie / John As you all know battery failure has been the most common failure mode for AMSAT spacecraft for a very long time. Patrick's idea of solar power only will be put into practice with this falls launch of a triple cubesat Delfi3C. It has a 40kHz linear UV transponder and no batteries. - Should be very interesting. However, solar power alone has its own problems. With changing angles between the panel and the sun the voltage or perhaps more accuratly, power, will change with change in attitude. Consequently the supply could drop out frequently unless there is some form of short term storage. Certainly there would need to be some form of sequencing so that vital control electronics are given priority over heavy curent parts of the payload. Super capacitors would be a really neat experiment but I wonder how they would react if a large energetic particle pentrates the capacitor when it's holding a large charge? Perhaps OK for LEO, maybe a bit risky for HEO through the radiation belts. There could be another approach. The batteries usually go short circuit pulling all power from the solar panels to ground. Ocassionally they go open circuit....as per AO-7. but this must be a rare event. Imagine a satellite PSU which uses a battery but has a solid state relay between the battery and the satellite buss. Solid state relays have very low on resistance and only need a couple of milliamps to keep them in the on position. For 5 to 10 years the battery could supply the few milliamps required to maintain the relay in the on position. When the battery eventually fails, if it goes short circuit it pulls all the power to ground and the satellite stops working. However, at that point the relay loses its couple of milliamps 'holding current'. At this point the relay open circuits and the faulty battery is isolated from the still functioning solar panels and the satellite is restored to life.....but only in sunlight. There may be a down side to this, but if there is I cant see it. I suppose every now and again the satellite CPU could supply a few milliamps to the relay just to see if the battery has recovered. If it has it will be charged and normal operation will be restored. If not, then the supply line will get shorted to ground via the battery and then the relay will open again restoring the satellite to solar only power. Have I missed the obvious or is this a neat idea? regards David G0MRF

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Re: Future radical satellite designs
by Patrick McGrane 08 Jul '07

08 Jul '07

hi maggie- sorry for being short with you. Thank you for the more detailed posting. For low power sleep mode or standby of control electronics, super capacitors become more practical and longer lasting than batteries. I believe someone in the group has or is experimenting with supercaps. One possible group to approach for inclusion of an auxilliary payload is NOAA since they are prolific satellite builders and have a preexisting relationship with the amateur community. Take care, pat ------- Original Message ------- >From : Margaret Leber[mailto:maggie@voicenet.com] Sent : 7/8/2007 10:05:41 AM To : amsat-bb(a)amsat.org Cc : Subject : RE: [amsat-bb] Re: Future radical satellite designs On 7/8/07, Patrick McGrane <N2OEQ(a)aceweb.com> wrote: > Hello maggie- I hate it when people snip or take things out of context. > Go back to the original entire email to absorb the reason. thanks, patrick I did read the whole thing. The challenges to amateur secondary payloads on commercial or military spacecraft have been discussed here at length in the past. *My* comment was that a standalone bird *designed* without battery-powered transmitters might be an interesting approach. As it stands now we have several birds on-orbit designed with larger battery systems (that have subsequently failed) that come up in various random control system states when they come out of eclipse. These birds only transmit when in sunlight anyway; what if we designed one that way on purpose? Now *that's* a "radical satellite design". The payload weight that would have gone to bigger batteries to power transmitters during eclipse could be used for other equipment. A smaller (more reliable? certainly simpler and cheaper) auxiliary battery system could keep the control systems alive during eclipse. A lot of work is being done with ultra-low-power processor chips for mobile applications these days. Imagine if AO-40 had used this approach (admittedly not at all in-line with the elaborate something-for-everyone AO-40 design philosophy); it might still be usable. As it is, when the complex power system failed, we lost the whole bird. And the only hope of recovering it is the outside chance that it might fail *again*. -- 73 de Maggie K3XS Editor, Phil-Mont Mobile Radio Club Blurb - http://www.phil-mont.org Elecraft K2 #1641 -- AOPA 925383 -- ARRL 39280 _______________________________________________ Sent via AMSAT-BB(a)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

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Future radical satellite designs
by Patrick McGrane 08 Jul '07

08 Jul '07

Greetings from Patrick N2OEQ Let me preface my comments by stating the following; The solar energy in space, outside the atmosphere, is approximately 1400 watts per square meter. This equates to about 130 watts per square foot. AO-51 ( amsat Echo ) is roughly a one foot cube covered with 27 percent efficient GaAs solar cells which cost approximately 20,000 dollars. With that efficiency and almost complete side coverage with solar cells, I would guess the satellite solar cell power conversion is about 25 to 30 watts for half the orbit time. Conservatively, that is about 300 watthours or more per day. Now, the transmitter might use 2 watts of energy to provide the 500 milliwatt downlink RF power and the satellite control electronics uses about 1 watt of energy. The Digital transmitter might use another couple of watts. For argument sake, I'll say the satellite uses 5 watts continuously for 24 hours per day or about 125 watthours per day. For some reason, it seems the full potential of the solar cells is lost or underutilized. The transmitters power is kept low to reduce the batteries depth of discharge to a minimum to extend the battery life. The point I am trying to make is that if amsat is going to pioneer new technologies in satellite design, they should keep their eye on the big picture or the basics of operation. I'm aware that people are trying to find a replacement for batteries but I would go further in saying that perhaps for future designs that amsat resort to solar dependant power output or specifically, full transmitter power directly powered by the solar cells and a sleep mode while the satellite is in darkness. >From what I have learned about satellites, batteries are the weakest link often spelling disaster and limited satellite lifetimes. I would rather enjoy a high power intermittent solar satellite for many years more than the average lifespan of one dependant on battery life and cycling. Some will argue that they want continuous duty whenever the satellite is in range, day or night. I would like to see a longer lived satellite capable of full power half the time that could potentially last several decades in orbit. Another point to ponder is the idea of asking to have auxilliary or piggyback payloads on larger commercial satellites. This was done with the russian RS satellites and more recently with India's Hamsat. The larger commercial satellites would probably have much larger and more efficient power budgets. I just read on the space.com website ( linked from amsat ) that the new Directv satellite is about 6 or 7 thousand pounds and probably utilizes the most advanced and reliable technology available. Wouldnt it be cheaper and easier to build an auxilliary payload versus an autonomous satellite? This question has probably been answered many times but I'll bring it up again. If it is a costly idea, is the additional cost justified by better, more reliable operation? Thanks for allowing this forum and thanks for all replies. 73, patrick

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Fwd: Future radical satellite designs
by Margaret Leber 08 Jul '07

08 Jul '07

On 7/8/07, Patrick McGrane <N2OEQ(a)aceweb.com> wrote: > Some will argue that they want continuous duty whenever the satellite is in range, day or night. > I would like to see a longer lived satellite capable of full power half the time that could > potentially last several decades in orbit. That's really insightful. So many of the birds end up operating in that mode *anyway*; what could be accomplished if we designed them that way on purpose? -- 73 de Maggie K3XS Editor, Phil-Mont Mobile Radio Club Blurb - http://www.phil-mont.org Elecraft K2 #1641 -- AOPA 925383 -- ARRL 39280 By the way, inbound email is broken on the address you're using: "SMTP Error (state 13): 550 5.1.1 <Patrick.McGrane(a)aceweb.com> is not a valid mailbox"

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