>Newsgroups: rec.radio.amateur.misc >Path: news.unomaha.edu!unlinfo.unl.edu!wupost!cs.utexas.edu!uunet!psinntp!digex!sgreene >From: sgreene@access.digex.com (Stephan Greene) >Subject: Summary - Getting onto the Hamsats >Message-ID: <1992Mar20.165707.3374@access.digex.com> >Keywords: Satellites, OSCAR, AMSAT >Organization: Express Access Public Access UNIX, Greenbelt, Maryland USA >Date: Fri, 20 Mar 1992 16:57:07 GMT >Lines: 249 On Wednesday, 11 March 1992, I posted a message to rec.radio.amateur.misc asking for suggestions and advice on equipment for using the amateur satellites. This article is a summary of the responses I received, as well as some related e-mail and news articles. A big thank-you to those who responded directly to my posting or posted a related article: mbutts@mentorg.com or mbutts@qcktrn.com (Mike Butts), KC7IT psmith@mozart.convex.com (Presley Smith), N5VGC rwa@cs.athabascau.ca (Ross Alexander), VE6PDQ gary@ke4zv.uucp (Gary Coffman), KE4ZV Andy MacAllister, WA5ZIB (via CompuServe's Internet gateway) Don_R._Moberly.El_Segundo@xerox.COM, WB6LFC Here's the consensus opinions (any misrepresentations or misquotes are my own - so flame me, not the nice folks who contributed!) Antennas: ------------ For AO-13, the consensus is get to get KLMs, Telex/Hy-Gains, or roll-your own, Nobody liked the Cushcraft satellite antennas - they appear to have problems in wet weather. Bigger is also better, if you have the space. Several people mentioned the KLM 22C and 40CX pair as excellent performers (again - you need the room for those long booms!) KE4ZV stated his pair of KLMs (the big ones!) lets him work AO-13 with 3 to 30 watts (hardline feed and rigorous attention to routing the feedlines a nd cables properly to maintain the antenna patterns helps, too.). Others mentioned the KLM 14C/18C pair as good performers - but you need more power on the uplink. Telex/Hy-Gain antennas were recommended by several people as a less expensive alternative to KLMs that work almost as well. There's also M2 (started by an engineer from KLM). While no one who responded uses them, the information I received from a call to their factory in California suggests they are comparable to slightly better than the KLMs in performance, and about the same in cost. Dave, WB6LFC, said homebrewing antennas is also feasible - it takes work, but attention to detail results in top-notch performance for very little money. Finally, Ross, VE6PDQ, reported good results using a pair of Cushcraft 215WBs on receive. Problems encountered with AO-13 antennas include routing cables and feedlines off the back of the antennas (to preserve antenna patterns), use of fiberglass cross booms, mounting preamps as close to the feedpoint as possible, and long antenna booms drooping. (Gary, KE4ZV, recommends using a rope to brace the boom or stiffening booms and fiberglass masts internally with foam-in-a-can insulation.) On antenna rotators, it appears the Alliance UD-100 is no longer made, though it should still show up at hamfests. People with long-boom antennas report the Alliance rotator is too weak to move a big array anyway, and recommended Yaesu's elevation-only rotator or their Model 5400 azimuth-elevation unit. Antennas for the low-altitude satellites appear to be much less critical. J-poles were most frequently mentioned (the design from the AMSAT Journal?), but dipoles, ground- planes, and yagis are also in use. Several people work RS-10 quite well with antennas in the attic. Best results are with steerable antennas, but the high operator workload during a pass (unless the satellite is just grazing your access circle) almost demands computer control of the rotators. Preamps: ----------- You need a preamp for AO-13. (I can hear the downlink after a fashion on a Ringo fed with cheap coax and a 10 dB preamp in the shack, but it's not communications quality reception!) Only two people mentioned a specific brand name (Advanced Receiver Research and the unit included with the Ten-Tec 2510), so I assume almost any GAsFET preamp in the 20dB gain class is adequate. THE PREAMP MUST (almost always) BE MOUNTED AT THE ANTENNA (check the discussion in Chapter 9 of the Satellite Experimenter's Handbook and you'll see why!). KE4ZV recommends mounting the preamp AT the antenna feedpoint, if your elevation rotator can handle the unbalanced load. While no one mentioned it (maybe it's obvious), if the antenna is used to transmit (say Mode J) as well as receive (on Mode B, for example), the preamp MUST either include RF-sensed switching, or be switched out of the line before you transmit. TRANSMITTING INTO AN UNPROTECTED PREAMP WILL DESTROY IT INSTANTLY! Preamps also seem to help on RS-10 (especially with older HF rigs) and on the Pacsats. It seems to be a case of "try it, and get a preamp if it looks like it would help"). Rigs: ------ Three radios were mentioned by name - Yaesu FT736 (and it's predecessor, the 726 with satellite module), Kenwood TR751 (a mobile-capable 2 meter multimode), and Ten-Tec's 2510. The Ten-Tec unit is out of production. The few units left are selling for about $300-350. I'm sure other multi-mode radios, and setups with converters and transverters work well, too - it's just that no one mentioned any by name. Power output required is a function of the satellite, your antennas, and how badly you want to communicate. [QRP on the satellites is just like QRP on HF - you need good antennas and feedline, you have to pick optimal passes, and skilled operators at both ends are needed. Given the apparent "calmer" operating style on AO-13, QRP is probably easier there than on 20 meters!] Anyway -about power for AO-13. 3-30 watts will work if you have top-notch antennas (KE4ZV). KC7IT uses 50-100 watts (Ten Tec 2510, Mirage D1010 amplifier, KLM 14C/18C fed with 50 feet of 9913). Both KE4ZV and KC7IT use Mirage D1010 amplifiers on 70 cm when they need a little extra power. For an "optimum station", WA5ZIB recommends 60 watts on 70 cm and 80 watts on 2 meters for AO-13, assuming good antennas (Telex/Hy-Gain or better) and feedlines, and 20 watts to a 5' dish for Mode L. Andy emphasized that you can get by and have lots of fun with much less! For Mode A, WA5ZIB said 6 watts to the AO-13 2 meter antenna will work well. People using omnis report success with the Pacsats running 50-70 watts to a J-Pole (N5VGC). Several people said they (or someone they know) have no trouble using RS-10 at lower power (10-25 watts) with simple, omnidirectional antennas. Again, it's a case of "try it and see if it works." There was unanimous consensus that the receiving quipment (antenna, preamp, feedline, and receiver) is more important than the transmit equipment. Running more power "to hear yourself" is frowned upon, to say the least! It's also important to be able to vary uplink power to adjust to specific conditions. Both the Ten Tec 2510 and the Yaesu 736 have continuously variable power output (I guess the rest of us just have to fiddle with the drive controls on our rigs!). Accessories and Other Stuff: ---------------------------------- You need a PSK modem to use the Pacsats. PacCom makes fully assembled units, either already integrated with their own TNC, or as a board you install in your TNC-2 clone. They make similar 9600 bps units for accessing UO-22. The downlink receiver (on 70 cm) should be capable of being tuned by the PSK modem's AFC lines. Newer radios can use the up/down lines from the microphone jack or an accessory connection on the rear panel. Older radios must be modified, or be tuned manually. N5VGC told me he sees about 20KHz of doppler on an AO-16 pass, and that without automatic tuning, operator workload is too high to do much else besides tune the receiver! Just about any radio suitable for packet on 2 meters will work for AO-16, WO18, and LU-19. To run 9600 bps on UO-22, modifications to bypass the microphone and speaker's audio processing circuits are required. I've seen some reports on rec.radio.packet and in the various Hamsat columns that differences between UO14 and UO-22's transmitters make UO-22 more difficult to copy. (I'll worry about that problem later - I'll start with AO-16 and LU-19 first!) No one mentioned computers - again, it must be obvious (also, we're "talking" using computers!). They're handy, and you need one IN THE SHACK when working the Pacsats or for automated, real-time control of antenna rotators (useful for low altitude satellites). Other operator aids mentioned, or I thought of on my own: If your radio can't slave uplink and downlink tuning (Ten Tec 2510 and Yaesu 736 can), you need something to help convert between uplink and downlink frequencies (and account for doppler shift and calibration errors on the radios' frequency readouts). A cardboard slide scale or dial will work. I'm thinking of programming my HP48 to do the conversion for me. You need something like this to know where to tune on the uplink to hear a given downlink frequency. Software to track satellites and predict passes. There are many programs that work. Price ranges from free to $70 for state-of-the-art QuickTrack or InstantTrack (available from AMSAT). Special software is also needed to use the Pacsats, and to interpret telemetry data. This software is also available from the usual ham sources, and from AMSAT (BTW, software sales support the amateur satellite program!) Polarity switchers optimize antenna performance by allowing switching antenna feeds from RHCP to LHCP as the need arises. They are a very useful add-on, but don't appear essential. Equipment to measure power output, SWR, transmit frequency - all useful (see - satellites are not that different from HF!). Conclusion: --------------- Finally, there's AMSAT! They're the people who build and run several of the satellites (AO-10, AO-13, AO-16), and have a hand in many of the others! They're also beginning development of the replacement for Oscar 13 (known as Phase 3-D). ANYONE INTERESTED IN THE AMATEUR SATELLITES SHOULD BECOME AN AMSAT MEMBER. Its' the closest place I've found to one-stop-shopping for information on the satellites (this newsgroup is number two, at least until I get onto the satellites myself!). You can reach AMSAT at: AMSAT PO Box 27 Washington, DC 20044 (301)589-6062 I know there are several AMSAT members in this newsgroup (who even have satellite experience. I'm still working on it!) - so you can always ask here! Again, thanks to everyone who answered my query! You've helped a great deal. I'll look for you on the birds! 73, Steve (AMSAT Member 21876) packet:: KA1LM@N4WJN.VA or KA1LM@WA3ZNW.MD Internet: sgreene@access.digex.com