Hi all, 1 or 2 degree per second is an educated guess for almost all passes. If the pass is "over head" the speed will increase up to 4/5 degree per second (as maximum value), such a speed is not achievable by all rotators.
Hope that helps, 73s Fabio IZ5XRC www.amsat.it On Mon, May 13, 2013 at 2:52 PM, Robert Bruninga <[email protected]> wrote: > One needs to also realize duration. The time say above 70 degree > elevation (where rates are highest) are less than 2% of the total pass > times. Not worth worrying about. Similarly, a LEO satellite spends 70% > of its time below about 22 degrees. (but it is far away and needs max > gain). So simply design for the best operation for most of the time when > the link will work. > > Remember, the satellite is 3000 km away on the horizon and very weak, but > as it gets into say 1500 km it is twice as close and 4 times (6 dB) > stonger which is a heck of a lot of gain. When it goes directly overhead > it is another 6 dB closer which is more than *ten* times the signal on the > horizon, so don't worry about the 2% of the time it is going to be above > 70 degrees. The signa is 10 times stronger and easy to deal with. > > Bob, WB4APR > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Art McBride > Sent: Monday, May 13, 2013 12:44 AM > To: 'Roger'; [email protected] > Subject: [amsat-bb] Re: ISS HamTV Frequencies > > Roger, > A SWAG, (Wild Guess) 1 degree per second at a Zenith of 90 degrees. > Anything less than 90 degrees will be slower with several minutes spent > near the horizon. You can use an orbital program to get exact numbers. > With a wide beam width antenna, the lag overhead may never require the > antenna to move with the object, as there will be time for the antenna > system to catch up after passing overhead. > Art, > KC6UQH > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Roger > Sent: Sunday, May 12, 2013 2:34 PM > To: [email protected] > Subject: [amsat-bb] Re: ISS HamTV Frequencies > > Anybody off the top of their heads know how many degrees a second swing > are (is?) required for direct aim at the ISS? I know there are beam width > tolerances, altitude variations and degree above horizon variations but > I'm looking at Bob B's fixed antenna aiming of 15-20 degrees above horizon > to evaluate swinging a dish without torque eating up the drive train... > > Roger > WA1KAT > On 5/12/2013 5:01 PM, M5AKA wrote: > > The AMSAT-UK page at > > http://amsat-uk.org/2013/05/12/hamtv-from-the-iss/ > provides the links, they are: > > > > Facebook https://www.facebook.com/Hamtvproject > > > > More information at > > http://www.amsat.it/Amsat-Italia_HamTV_brochure.pdf > > and http://www.amsat.it/Amsat-Italia_HamTV.pdf > > > > The HamTV.pdf gives the link budget, looks like there's 7dB of > coax/connector losses to overcome between the ISS transmitter and the > antenna. That document indicates a 90cm dish should be sufficient. > > > > I believe that it's going up on ATV 4 which is currently slated for > > June > 5. > > > > 73 Trevor M5AKA > > > > > > _______________________________________________ > Sent via [email protected]. 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 > > _______________________________________________ > Sent via [email protected]. 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 > _______________________________________________ > Sent via [email protected]. 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 > _______________________________________________ Sent via [email protected]. 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
