[amsat-bb] Re: eggbeater rx performance
n3tl at bellsouth.net
Fri May 29 21:54:46 PDT 2009
Greg and all,
I must respectfully disagree - unless we have different definitions of what constitutes a fair signal. The carious satellite-description pages on the AMSAT Web site include information about transmit power for all of the satellites. All of them except AO-7 are transmitting nominally at power levels less than 1 watt.
If anyone following this thread remembers the special operating mode the ISS repeater was in during December, for the 25th anniverary, you may recall that ARISS announed it would be a "low power" operation, which I believe meant 5 watts out. Somebody correct me if I'm wrong about that. Even at 5 watts, the ISS, was so strong one almost didn't have to Doppler-tune for the downlink, and it was on UHF! For the special operating period, they put the repeater in Mode J instead of the usual Mode B.
My point is that the ISS, which is in an orbit quite a bit lower than our satellites, was transmitting with more than 5 times the power of our FM and most of the linear satellites. My experience with mobile operation has been that I do best with AO-27 and SO-50. Both of them use 0-gain, quarter-wave verticals mounted on one corner of the satellite.My vertical likes their verticals ... hihi.
Dave is right about the quadrafiliars, by the way - I just saw his post come in as I was typing this. Contact Allen, N5AFV, who has picked up one of the Antennas US quadrafiliars, and he's using it mobile with pretty good success.
Eric, if you're interested in truly mobile operation, your decision will involve a compromise. You will not get the same "coverage" during a pass that you get with either the Arrow or the Elk when you are parked and pointing. Your "operating window" will be more narrow. But it's definitely do-able. I was shocked to work Craig, KL4E, in Anchorage a couple weeks ago from southwest Missouri. We worked on AO-27, and I was using my Yaesu VX-7R HT and an MFJ 1729 dual-band mag mount. That pass was a maximum elevation of 16 degrees to my location, which was just east of Seymour, Mo., along the side of U.S. 60 on a county road. I had about a minute of readable copy, and I was in a location with a "look" toward the satellite that was flatter and more unobstructed than what I routinely deal with at home. If I'd gotten to that spot in time to assemble the Elk, I would have been able to work from at least 3 degrees elevation coming up to 3 degrees going down. That's my nominal AOS/LOS cutoff with the handheld Elk. Using the Elk would've given me several minutes of the pass, instead of just 1 on the vertical. That's where the compromise of an omni directional antenna comes in.
Whichever way you go, have fun with it!
Thanks, Mark, for the kind words about the operating Patrick and I are doing with our portable stations. It far exceeds anything I expected.
73 to all,
Tim - N3TL
Athens, Ga. - EM84ha
-------------- Original message from "Greg D." <ko6th_greg at hotmail.com>: --------------
> Many years ago I worked the MIR space station while driving to work. I was headed West on I-80, and MIR had just come up on the horizon. Admittedly it had a lot higher power, and a lower orbit, but he was full quieting on FM into my Larsen 2/70 glass mount. I wouldn't be surprised if you could get a fair signal
> with a whip antenna and a good preamp running SSB on FO-29.
> I'm not going to encourage anyone to operate CW while driving! Even for SSB, get your rig hooked up to a small laptop with automatic doppler tracking, and set it up before departing, or you might just shift yourself off the road and
> into a tree. That might damage the rig.
> Greg KO6TH
> > From: mlunday at nc.rr.com
> > To: eric.fort at gmail.com
> > Date: Sat, 30 May 2009 00:10:32 -0400
> > CC: amsat-bb at amsat.org
> > Subject: [amsat-bb] Re: eggbeater rx performance
> > Good question. With Arrow/Elk, it is directional. Good gain but not omni.
> > With whip it is omni, but reduced gain.
> > Don't know of anyone who operated while driving, so I cannot help you with
> > that one. Maybe eggbeater is the way to go.
> > Mark Lunday
> > WD4ELG
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