AMSAT-BB September 2009

228 participants
393 discussions

Call for Papers--2007 ARRL/TAPR Digital Communications Conference

by Ford, Steve, WB8IMY

Technical papers are solicited for presentation at the 26th Annual ARRL and TAPR Digital Communications Conference to be held September 28-30, 2007 in Hartford, Connecticut. These papers will also be published in the Conference Proceedings (you do NOT need to attend the conference to have your paper included in the Proceedings). The submission deadline is July 31, 2007. Please send papers to: Maty Weinberg ARRL 225 Main St Newington, CT 06111 or you can make your submission via e-mail to: maty(a)arrl.org Papers will be published exactly as submitted and authors will retain all rights. 73 . . . Steve, WB8IMY ARRL

10 years, 2 months

Re: EggBeater

by Bill Dzurilla

Steve, I have both a commercial and a homebrew Eggbeater and am disappointed with both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than with an HT and an Arrow. Guess an omni can't cut it, at least not from my QTH. Maybe if I could get it up higher, clear of all roofs, it would do better. I can make contacts at relatively high sat elevations, but can do just as well with a $10 dual band ground plane. My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better, down to 10 degrees elevation in some directions. Good luck and 73, Bill NZ5N > > Hi Steve, > > > > It is surprising to read that you are not hearing > anything. I have > > repeatedly used a 2m and 70cm Eggbeater for the sats > and have had no > > problem hearing things. No pre-amp. > > > > I was using a short cable (e.g. less than 10 meters). > The rigs I > > used were a FT-736r (deaf) and a FT-847 (so-so). > > > > 73, > > > > Dave

10 years, 3 months

FW: Re: The Moon is our Future

by Dave

We have met the enemy and they are us. WE need to do something. Yes, $15m is outta reach, but isn't there a cash prize for the first on-commercial moon landing? Dave DM78qd // KA0SWT If it weren't for Philo T. Farnsworth, inventor of television, we'd still be eating frozen radio dinners.-- Johnny Carson +++++++++++++++++++++++++++++++++++++ -----Original Message----- From: amsat-bb-bounces(a)amsat.org [mailto:[email protected]] On Behalf Of Jeff Davis Sent: Thursday, July 02, 2009 9:35 AM To: amsat-bb(a)amsat.org Subject: [amsat-bb] Re: The Moon is our Future On Thu, Jul 02, 2009 at 06:48:51AM -0600, Jack K. wrote: > communications anyway) and move forward... We can put up all the leos > we want, but until someone makes something like B. Bruninga's cell > concept work, we are only going to have more of the same, We don't > need more of the same! I couldn't agree more - we don't need more of the same. If I want to sit back and have a two hour rag-chew with someone on the other side of the planet I will use Skype or my cell phone! Dreaming about what *might* be in space is a fun exercise. Actually doing something about it requires sending things to LEO because reality has dictated that's as far as we can afford to go. How's about we use some of that frustrated *imagineering* to come up with interesting new concepts at LEO? We don't need any more FM repeaters buzzing overhead, but what about more cameras downloading HD images, scientific payloads that monitor the ongoing climate change, payloads to study the Earth's magnetic field, etc. etc. Our own 'Twitter' messaging network from space...? The Apollo 13 creed of "failure is not an option" has completely infected the brains at AMSAT and this list. You want something at HEO or on the moon, cut a check for $15 million dollars and let's get on with it. Been waiting since 1996 for another AO-13 and I am getting too old to keep waiting. AMSAT is becoming completely irrelevant as it strives without success for the impossible mission and exhibits a shocking amount of leadership malfesance as it stubbornly refuses to recognize and adapt to realities in the launch business. I know, I know maybe NEXT year someone rich will die and leave us a boatload of cash. Or the bankrupt US government will suddenly cough up a billion dollars for some orbiting emergency communication system. In the meantime we have to stifle the truth because it might blow yet another *secret* deal that's in the works and *almost* a done deal, so let's not complain publicly and ruin it. Heard the stories, heard the lies, got all the t-shirts and ball caps. Whatever. -- Jeff, KE9V AMSAT-NA member since 1994, Skeptic that we will ever go back to HEO since 2002 _______________________________________________ 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

11 years, 6 months

Not everyone is working on ARISSat-1

by Alex, N3SQ

There are some of us out here who are trying to bring a little order to the chaos and help AMSAT, but we are all not working on ARISSat-1. Our effort lies in the following vectors and scalars: - Change needs to be EVOLUTIONARY not REVOLUTIONARY. - Chaos can be harnessed with the correct application of traceability. - The future leads through the correct application of effort There are clouds of dust on the horizon . . . . . with the sound of many hoof-beats in the distance . . . . . is that a bugle call-to-arms I hear on the wind? Those who know, understand. Those who need to know will find out soon enough. I will leave you with these two thoughts until next time . . . * Look to the Empire State near the Harvest Moon. * A gift may arrive near the ides of May. *Dobranocz*

12 years, 11 months

Satellite Orbit Prediction in Python

by Mark VandeWettering

I just thought I'd drop a quick note here about some fun I've been having today with satellite orbit prediction in Python. When I started mucking around with satellites, I used "predict", which was pretty good, but at some point I wanted to answer some questions which weren't easy to answer using predict. Questions like "when will AO-51 be visible from both my home in CM87 and locations in Hawaii", or "what was the radius of the circle of visibility for AO-7 compared to ISS"? Luckily, I'm a programmer. In fact, I'm a programmer who programs for fun. So, I did a bit of research, and then coded up a version of G3RUH's "Plan 13" algorithm in Python, and then wrote some scripts to download elements from celestrak, and then a simple one to print data on the next pass of any named satellite. And, they worked pretty good. I've used them for the last year or so to do all my pass predictions. But there are still a couple of minor issues with the library. It didn't handle geosynchronous satellites very well. It implemented only the most basic of orbital models. I was never confident that the "is this satellite in eclipse" stuff working exactly right. Luckily though, it turns out that someone else has been busy writing a more complete library: PyEphem http://rhodesmill.org/pyephem/ It's a library whose primary purpose is to calculate the positions of astronomical objects. I've used it a couple of times to (for instance) figure out the size of Mars compared to Jupiter, and found it very easy to use. But today, I realized that it had a full implementation of the SGP4 and SDP4 orbital models built in, and could be used to predict satellite passes. As a proof of concept, I hacked together a 23 line script that could print the details of upcoming ISS passes. It seems to work great, and is really quite easy to use. You can find some of the simple example code at my blog: http://brainwagon.org/2009/09/27/how-to-use-python-to-predict-satellite-loc… I'll probably be porting all of my existing scripts to use this soon. In the mean time, if you have a similar task, you might look to it to solve your custom satellite prediction problems. 73 Mark K6HX

12 years, 11 months

Arrow antenna reconfiguration results - UPDATE

by Jeff Yanko

Hi all, A quick update to my new project to improving the Arrow antenna, efficiency wise. I wanted to see how well it would perform on gaining and losing access during AOS and LOS. AO-27 is not a good choice since the timer is turned on when it is well above the AOS horizon and it is switched off before it reaches its LOS horizon. That leaves a dependable AO-51 to test it out. With the last setup, the OEM diplexer provided by Arrow Antenna, I would copy AO-51 about 3 minutes after AOS and lose it about 3 to 4 minutes before LOS. Not bad, but people were saying they worked the birds when they were 1 degree off of the horizon. I have some pine trees that could be an issue but they are spaced far enough apart that I can work between them and I also have to deal with the McCollough Range to the SSE of me here in Las Vegas, NV. Today, there were 2 passes of AO-51, one at 12 degrees elevation, the other at 74 degrees. During both passes, I began to copy the downlink about a 1.25 minute after AOS. A considerable difference from 3 minutes. The downlink also improved down to about minute before LOS. On the last pass I worked KG6NUB at 0124z and LOS was 0125z and my downlink sounded fairly good, though I was fighting desense. (That's another issue I need to resolve.) Also, on both passes, I never once lost the downlink. No dropouts or fades. I'm still amazed. Another issue I came across was how wide the beamwidth is of the Arrow Antenna between the Arrow diplexer and the new diplexer. I was wondering if this was going to happen and it did. The reason that this happened was with the old diplexer, the signal attenuated so much that you had to be pointed right smack dab on the bird, a few degrees off and you lost the signal. Now, with the new diplexer, you can point the beam in the general direction and still copy the bird. In most cases I had to turn the beam 90 degrees before I completely lost the downlink! Twisting the antenna to make polarization changes makes absolutely no difference now. This also attributes to the fact that now I'm copying the entire pass without dropouts or fades. Makes sense. What I've regained over the lossy diplexer makes up for any polarization differences, etc. for a better copiable signal. Next weekend I will have to try more passes and get a feel of how much this system has changed. 73, Jeff WB3JFS Las Vegas, NV DM26

12 years, 11 months

quadrafilar helix for 70cm- ambiguous design specs

by Tim Goodrich

Hi All, The house I just bought precludes me from even using my arrow inside as there must be something un-RF friendly in the walls. Therefore, I was looking for a roof antenna and the October QST article on the QFH inspired me to build one. However, after doing some research, I have come up with two sets of design specs and I'm unsure which one is correct. I converted everything from you're the 146Mhz QST model to 436Mhz. However, when I plug that info into http://www.jcoppens.com/ant/qfh/calc.en.php The values it puts out are different in the "compensated length" field. The only difference is this model calculates for a full turn as opposed to a half turn, but the lengths shouldn't be as different as it says. Under the QST model, I get a wavelength of 688mm, but under the website's model, it gives me a "compensated wavelength" of 729mm. The values I used to calculate are: 436 1 1 15 2 .23 Can anyone tell me which specs to use and/or explain this compensated wavelength issue? Thank you, Tim KI6VBY

12 years, 11 months

Cute 1.7 Re Entry Competition

by John Heath

Hi folks, Thanks for the entries so far. It has been pointed out that I didn't allow much time, so the closing date is now one day later, midnight October 1st To enter this fun competition send me your best estimate for the re-entry date and time for Cute 1.7 Object 28941 Spacetrack suggests October 10th but I think it will be several days later. The prize for the closest prediction is a 2.4GHz patch antenna kit as shown on the Amsat-UK shop page under hardware. 73 John G7HIA

12 years, 11 months

College Satellite nights, Thursday night

by Dr. Jay Garlitz

Don't forget to work the Thursday evening passes and listen for, and work, college club stations. On AO-51 we'll be on the QRP transponder. AO-7 should be in mode B that evening. HAMSAT has been little used and is a great bird, with some nice passes that evening. Activity will be centered on passes starting Thursday Oct. 1st 22:00 UTC through 05:00 UTC. U of Kansas (K0KU), Stanford (W6YX), UF Gators (W4DFU) and Rochester IT (K2GXT) have already confirmed they will be on. Other clubs have been active during past events including U Michigan, Michigan State U, U Kentucky. U Arkansas, Naval Academy, and others. Please give college station priority on the QRP transponder on AO-51 that evening and let them work everyone they can. No good deed should go unrewarded.look for an award certificate program in the near future for working college club stations on satellite. We have asked the clubs to QSL those that they work and appreciate your patience in letting the club stations have priority for the evening. Jay, AA4FL

12 years, 11 months

Kursk experiment on ARISSAT-1

by Bruce Robertson

It's great to see the diagrams of ARISSAT-1 up on the web site: congratulations to KF4KSS and everyone who contributed. Can anyone describe the nature of the experiment from Kursk University that is going to be included in the satellite? 73, Bruce VE9QRP

12 years, 11 months

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AMSAT-BB September 2009