February 2010 - AMSAT-BB - mailman.amsat.org

AO-51 Signal Strength Post Flip
by John Papay 10 Feb '10

10 Feb '10

It has been about a month now since AO-51 was commanded back to its normal orientation. But many are reporting that they are having more trouble hearing it now than they did before the first re-orientation. It does seem to me that some stations that usually hear very well are not hearing that well now. This morning's pass (9Feb2010 1045z) of AO-51 seemed to bear that out. AF6RF, KB1RVT, KE3LB, WD0X?, KJ4CBC, K5QXJ, WB2IOL and YF6BFE were on the pass and with a few exceptions, all were not able to hear at some point during the pass. There are also a few noisy uplink transmissions as well. The recording can be downloaded at: http://www.papays.com/AO-51_09Feb2010_104452za.mp3 (there are no signals in the first minute of the recording) Is anyone else having trouble hearing AO-51 as well as they heard it before the flip experiment? 73, John K8YSE

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Office Closed
by Martha 10 Feb '10

10 Feb '10

Due to blizzard conditions today, the AMSAT office is closed. -- 73- Martha

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Down East Microwave 2355LYK 1.2GHz 55 elements loop antenna
by Juan Antonio Fernandez 10 Feb '10

10 Feb '10

Have anyboy worked with this 55 elements loop antena for 1.2 GHz. What about its mechanical and electric features? Juan Antonio EA4CYQ

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Good Night, Loran
by Howie DeFelice 10 Feb '10

10 Feb '10

Minor clarification, Loran-A was used from WW-2 until it was turned off in the 1980's I believe. The current system, Loran-C was in commercial use starting in the late 70's. When Loran-C was used for returning to a previously stored waypoint, it's accuracy was almost as good as current GPS and better than the early "dithered" commercial GPS service. Howie AB2S _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. http://clk.atdmt.com/GBL/go/201469229/direct/01/

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Re: New Lindy's QRV
by Clint Bradford 10 Feb '10

10 Feb '10

I read that article, and when I got to the last of it and he mentioned that he was using a pre-amp for working the FM birds, I wondered out loud: "Why???" We're working '27, '50, and '51 with HTs and meager antenna improvements. Better yet, build a tape measure Yagi - you can realize great gain with about six bucks of parts. Note that I haven't mentioned, "Buy a pre-amp" anywhere. I was considering building one of those antennas mentioned in QST last month - until I read that he was using a pre-amp. I'll just stick with what works for me ... home-brew or commercial Yagis ... a log periodic every now and then ... and no pre-amp anywhere. Clint, K6LCS http://www.work-sat.com

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Re: New Lindy's QRV
by Clint Bradford 09 Feb '10

09 Feb '10

>> ... Does it -matter- if he uses a preamp on FM, SSB, or freaking two cans and a string? Absolutely not. It has just been my "mantra" the past four years advising folks that you do not need 100 Watts of TX power, expensive Yagis on the roof, and a rotator under computer control to get into working the FM satellites. Now, then, if I lived in Drew's neighborhood, all that equipment sounds pretty appealing ... working the birds while adding fire to the fireplace with a hot toddy (or three) at hand. Clint, K6LCS

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Good Night, Loran
by Clint BRADFORD 09 Feb '10

09 Feb '10

In a series of small ceremonies, the U.S. Coast Guard on Monday shut down Loran-C, a navigation and timing system that has guided mariners and aviators since World War II. The death blow came last May when President Obama called the system obsolete, saying it is no longer needed in an age in which Global Positioning System devices are nearly ubiquitous in cars, planes and boats. Killing Loran-C will save the government $190 million over five years, Obama said. But supporters of Loran -- including the man known as "the father of GPS" -- say the nation's increasing reliance on GPS paradoxically has increased the importance of maintaining Loran as a backup. At 3 p.m. Monday, the U.S. Coast Guard turned off Loran signals at 19 of the 24 Loran stations. Signals remain at five stations because of agreements with Russia and Canada, but the Coast Guard expects those stations to be decommissioned by June after the United States receives verification that those countries have been notified of the change. The five stations that temporarily remain on line are at Attu, in Alaska's Aleutian Islands, and Caribou, Maine; Nantucket, Massachusetts; Shoal Cove, Alaska; and George, Washington. - from CNN/Reuters Clint Bradford, K6LCS

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Re: John's take on AO-51
by Robert Smith 09 Feb '10

09 Feb '10

Aloha All In general, Hawaii is a very quiet place. Most passes of AO-51 fly by with no usage. Accordingly, signal strength and quality are usually quite discernable (assuming no anomalous QRM) when QSOs do occur. The initial reorientation of AO-51 was very apparent here. In general, the bird appeared to have less signal strength and more fades. It was, SO-50 like. Since reorientation, it is my impression that the signal strength has improved significantly but there remain some fades; especially at lower elevations. In discussions with KG6NUB and others, the feeling is that the bird is still in some kind of "recovery mode." To me, "51" now seems like its old "self." Fades are becoming less prevalent. Finally, my knowledge regarding orientation, reliability and stability of OSCAR satellites is extremely limited. The concept of "recovery" may not even be applicable. Perhaps the AO-51 team can shed some light on the results of the overall experiment. 73 and Aloha to all. Respectfully, robert NH7WN, Honolulu

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Re: New Lindy's QRV
by Bill Dzurilla 09 Feb '10

09 Feb '10

Dave, I would be suspicious of the construction. I can get a few minutes of good copy from AO-51 on a high pass with just a rubber duck on an HT. If you do get a preamp, the run between the antenna and the preamp is critical, so if possible keep it short and use good coax. Ed seems to be having success with 4' of RG-58U, but generally the use of any RG-58U at 70cm is not a good idea. Here's a quick summary of my results with various antennas: * HT and rubber duck or other antenna mounted directly on the HT - success only at high elevations * HT and Arrow or Elk antenna, no preamp - success from horizon to horizon, if no trees or other obstructions * base rig and dual band omnidirectional ground plane, no preamp, 40' of RG-213U - success on most birds only when elevation is above 25-35 degrees * base rig and dual band omnidirectional ground plane, ARR preamp, 40' of RG-213U - success on most birds when elevation is above 15 degrees * base rig and Elk antenna on 12' pole at 15 degrees fixed elevation, azimuth rotation with old TV antenna rotor, ARR preamp, 70' coax run (my current setup) - full success from horizon to horizon on all birds, except in directions where blocked by trees or roof. The Elk is $135 shipped and the used rotor was $25, and this combo is by far the most effective I have used. My community has antenna restrictions, but so far no one has complained about the little 2' long Elk. The Elk could be replaced with a homebrew Cheap Yagi or tape measure yagi, which can be built for $10. I am not aware of anyone who is able to work the sats at low elevations with any type of omnidirectional antenna, even with the best preamp. You can have plenty of fun working the birds at higher elevations, but you will be able to work more passes and better DX (e.g., Europe on AO-7) if you can catch them at lower elevations. 73, Bill NZ5N > Date: Mon, 08 Feb 2010 17:26:11 -0700 > From: David Ek <dave(a)eksfiles.net> > Subject: [amsat-bb] Re: New Lindy's QRV > To: amsat-bb(a)amsat.org > Message-ID: <4B70ABA3.9090908(a)eksfiles.net> > Content-Type: text/plain; charset=ISO-8859-1; > format=flowed > > Question for anyone out there: I just built the parasitic > Lindy from the > Feb 2010 QST. What kind of performance (on receive) should > I expect from > it during, say, an AO-51 pass (max EL 83 deg)? I had my > Kenwood TH-F6a > HT connected directly to it (only a few feet of RG-8X coax > to the > antenna) with no preamp, and I only had good copy for a > moment here and > there. Just wondering if I need a preamp or if I need to be > suspicious > of my construction. > > tnx & 73, > > Dave NK0E > > ----------------- > > Edward Cole wrote: > I forgot to add that these are patterned after Tony, AA2TX, > designs > (UHF version is in Feb. 2010 QST). > My variation was to use pvc sched-40 plastic pipe (white). > > The preamp is one of the older DEMI designs that uses a > mgf-1302 > GasFet with about 0.7 dBNF. I see about one s-unit of > noise when I > turn it on. There is 4-feet of RG-58 to the UHF Lindy > and 60-feet to > the FT-847 from the preamp. The VHF Lindy has no > preamp and is fed > with 60-feet of RG-213. > > The VHF Lindy brings up repeaters 70-miles away with 50w, > and the UHF > Lindy hears repeaters that far away. So actually can > make a nice > general purpose antenna. > > 73, Ed >

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Tracking - End-stop Problem
by Clive Wallis 09 Feb '10

09 Feb '10

Hi, A problem that I've had for many years is how to track when the satellite's azimuth crosses across the rotator's end-stop, ie. when the azimuth changes from 0 to 359 degrees. My rotator turns between 0 and 450 degrees, so it should be possible to use angles between 360 and 450 to overcome a sudden transition from 0 to 360 degrees. As the pass data is available within the tracking program, it should be feasible to deal with the problem in the program. Do any tracking programs include this feature? A possible solution would be to use a small PIC between the computer and tracker, which could modify the commanded azimuth. I'm using a Yaseu 5500, LVB tracker, Sat_Explorer tracking program and WinXP. Any help, suggestions or comments would be most welcome. 73 Clive G3CWV Hitchin, North Hertfordshire, UK

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