July 2008 - AMSAT-BB - mailman.amsat.org

Fox Delta ST3 problem
by morry＠tekinnovations.com.au 27 Jul '08

27 Jul '08

Hi all, I have a Fox Delta ST3 interface, and I can't get it working properly. So far I have: Adjusted the full scale on the 5500 as per the manual. Set the output adjust voltage to 4.5 (also tried 4.7) volts. When the ST3 says 360 degrees, the 5500 display says around 290. It's almost like it was not designed for a rotator that turns 450 degrees (I know this is not the case). I even set the rotor to 360 degrees and tried to adjust the output adjust voltage to get 360 on the ST3 - there was not enough range! We have two of these units and both behave the same. Our home made interface works fine! Any ideas? Morry VK4HBK

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Re: Delfi C3 transponder frequencies ?
by Alan Cresswell 27 Jul '08

27 Jul '08

Hi David, The frequencies I indicated were the satellite input/output frequencies as I saw them here. My transmit and receive frequencies were those frequencies +/- Doppler It seemes to me that there is a 6kHz offset within the satellite transponder. I presume the Delfi team can tell us what the actual situation is. Alan ZL2BX _____ From: G0MRF(a)aol.com [mailto:[email protected]] Sent: Sunday, 27 July 2008 21:14 To: alancresswell(a)xtra.co.nz; oz1my(a)privat.dk Subject: Re: [amsat-bb] Re: Delfi C3 transponder frequencies ? In a message dated 27/07/2008 20:27:18 GMT Standard Time, alancresswell(a)xtra.co.nz writes: Hi all, On the one good pass over ZL so far I had to use a +6kHz offset on my uplink to receive on the nominal downlink frequency. i.e. satellite input frequency of 535.556 (nominal 435.550) to hit the 145.900 satellite output frequency. Alan ZL2BX Hello Alan Hello Ib That's quite a spread of frequencies 556 to 565. Was that corrected for doppler? I suppose the other possibility is that Alan has been listening towards the end of the pass when the satellite has reached its maximum temperature and drift? This will be interesting to follow! Sorry not to see you at Surrey this year Ib. Hope everything is OK Regards David

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VHF UHF Rig
by Mike Miller 27 Jul '08

27 Jul '08

Thinking about selling 847.....Which rig is best for satellite..work.? ICOM 910 H Kenwood 2000 opinions ....your 2 cents Mike Miller KA5SMA

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Delfi C3 transponder frequencies ?
by OZ1MY 27 Jul '08

27 Jul '08

Hi all, The transponder was working at the pass with AOS at 0926 UTC here in Copenhagen. Had a couple of QSOs with HA2RD and PE1ITR. As far as I can make out the frequencies are different from the published ones. Just after the transponder was turned on I har to go to an uplink of 435.565 MHz to get 145.900 MHz down. This is the nominal pair I used in SatPC32. After some time had to adjust the uplink down to 435.563 MHz. Can someone confirm this ? 73 OZ1MY Ib

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Re: LEO launch?
by G0MRF＠aol.com 27 Jul '08

27 Jul '08

In a message dated 27/07/2008 19:32:26 GMT Standard Time, w7lrd(a)comcast.net writes: Near the end of this article they mention a LEO launch vehicle. Something to think about! http://www.comcast.net/articles/news-science/20080726/TEC.Space.Tourism/ 73 Bob W7LRD Seattle Hi Bob. Sadly I think the general approach to Virgin Galactic's space tourism is incompaible with small satellites as we know them. The Virgin / Rutan plan takes people into space, but with zero relative velocity to the earth. This means that gravity will cause their spaceship 2 and any satellite to fall straight back down. To achieve orbit, the satellite would need propulsion capable of generating about 18,000 miles per hour of 'horizontal' motion + a bit more altitude would be nice too. Easier than launching from the earth. No friction from the atmosphere, but still a very difficult task. 73 David

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Dish surface 'flatness'
by Peter Ellis 27 Jul '08

27 Jul '08

I am now the proud owner of a very 'second-hand' 3m mesh-covered skeleton dish. The mesh covering is metaphorical, rather than actual. I watched the dish on its back while as a group of small children rolled the dish back and forth and trampled holes in the mesh. That's the reason I was able to ask for it. "Please take it away," was the manager's reply to my query. Now, I need to re-mesh the dish, but I need to decide what 'flatness' ('true-ness') the surface should be. There has to be a formula, that encompasses things like: frequency of operation, curvature or focus distance, etc. I've done some looking online, but can't find it readily. Suggestions, and discussion, please? Please note: If you're going to also make product, brand name, or supplier suggestions, then be generic as suppliers and products in VK (Australia) will differ from where most list members will be sited. With thanks, Peter VK1KEP

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LEO launch?
by w7lrd＠comcast.net 27 Jul '08

27 Jul '08

Near the end of this article they mention a LEO launch vehicle. Something to think about! http://www.comcast.net/articles/news-science/20080726/TEC.Space.Tourism/ 73 Bob W7LRD Seattle -- "if this were easy, everyone would be doing it"

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DELFI-C3 transponder report 09:38
by Rob Hardenberg PE1ITR 27 Jul '08

27 Jul '08

Hi All, I saw the delfi-c3 command team on video from the uk amsat weekend sitting with the laptop while the sat was on AOS. My thought: They are switching on the transponder! And yes :-) wkd: DL1YDD, OZ1MY, IW5EJM and DG0ER Great signals! Sometimes Freq Modulaton on the downlink signals 73 Rob PE1ITR http://www.pe1itr.com

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Re: AMSAT-BB Digest, Vol 3, Issue 375
by James Whitfield 27 Jul '08

27 Jul '08

Peter Ellis, vk1kep: I hope that you will get "better" answers from others of the group that have practical rather than theoretical experiences with large parabolic reflectors. My only qualifications on this subject come from experience as a Geometry teacher and limited amateur astronomy, but for what it is worth, here are my thoughts. The simple answer to the necessary "flatness" is better than a quarter wavelength error. The general idea is that the radio waves you want to capture come to the "ideal" reflector and all of them bounce back to a focal point, and all of the waves reaching that point at the same time, that is "in phase". The error of the real surface translates into a phase shift. If a substantial surface area is a quarter wave behind the ideal and if an equal area is a quarter wave in front of the ideal, then the waves from the two areas will be half wave apart, causing full cancelation. The quarter wave error is used to indicate that the maximum error difference from a high point, relative to the ideal, to a low point is no more than a quarter wave. That way the wave error causes phase shift rather than cancelation. A greater error probably will provide some "gathering" of the signal, but if you want to have a parabolic reflector that all of its aperture is effective, then you need the surface to meet the quarter wave flatness. As with optics, the less the error, the better the "image" that can be resolved. As a practical matter on radio frequencies, trying to exceed quarter wave is not worth the effort. You did not state if the framework was in good enough shape to serve as a template for the ideal parabola. If it is not, I can give you a formula, but I will need more information about the dimensions of the dish. Best Wishes. James n5gui > Date: Sat, 26 Jul 2008 08:00:26 +1000 > From: Peter Ellis <vk1kep(a)gmail.com> > Subject: [amsat-bb] Dish surface 'flatness' > To: amsat-bb(a)amsat.org > Message-ID: <488A4CFA.6060703(a)gmail.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > I am now the proud owner of a very 'second-hand' 3m mesh-covered > skeleton dish. > > The mesh covering is metaphorical, rather than actual. I watched the > dish on its back while as a group of small children rolled the dish back > and forth and trampled holes in the mesh. That's the reason I was able > to ask for it. "Please take it away," was the manager's reply to my query. > > Now, I need to re-mesh the dish, but I need to decide what 'flatness' > ('true-ness') the surface should be. There has to be a formula, that > encompasses things like: frequency of operation, curvature or focus > distance, etc. > > I've done some looking online, but can't find it readily. > > Suggestions, and discussion, please? > > Please note: If you're going to also make product, brand name, or > supplier suggestions, then be generic as suppliers and products in VK > (Australia) will differ from where most list members will be sited. > > With thanks, > Peter > VK1KEP

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FO-29
by rm2642＠aol.com 26 Jul '08

26 Jul '08

Northerly pass?footprint was coast to coast but only three users?counting myself. FO-29 works?great on SSB. Thanks to JARL. Ron N6PAA

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