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: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Roger Sent: Sunday, May 12, 2013 2:34 PM To: amsat-bb@amsat.org 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
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