[amsat-bb] Oscar Locator
Saguaroastro at cox.net
Mon May 30 03:58:30 UTC 2016
The ARRL store sells an evaporator for $1.00,though from the looks of it, it is just map portion, no mention of overlays..
Rick Tejera K7TEJ
Saguaro Astronomy Club
Thunderbird Amateur Radio Club
On May 29, 2016, at 15:44, James Duffey <jamesduffey at comcast.net> wrote:
Kevin - I used a Oscarlocator for many years, starting with Oscar 7 and moving up through the various RS birds until I got tracking programs for my computer.
This is from memory. My Oscarlocator is packed away somewhere, its existence obscured by at least two moves.
The Oscarlocator can be thought of as an analog computer. The background was an earth projection centered on the North Pole. There were two overlays for each satellite. One was the ground footprint of the satellite with azimuth markings on it and concentric circles for elevation. This overlay was attached to the background centered on the user’s QTH. The second overlay was the satellite ground track. The ground track was marked with tick marks that were labeled in minutes, with the mark corresponding to the equator being zero. The second overlay could be rotated with respect to the background.
To use the Oscarlocator, one needed equatorial crossing longitudes and the corresponding times for the equatorial times. These were published in QST, 73, the AMSAT Journal which for part of the time was known as Orbit, ARRL?AMSAT bulletins, and disseminated on the HF AMSAT nets. Having the crossing and time, one lined up the 0 tick mark on the ground track overlay with the appropriate equatorial crossing longitude. Knowing the equatorial crossing time, one then looked at the tick mark where the ground track intersected the footprint, added that to the equatorial crossing time to get the time for acquisition of signal. Azimuth and elevation could be picked off from the azimuth and elevation marks on the footprint. Similarly, when the ground track left the footprint, loss of signal occurred. I used this with fixed antennas for much of the time, so did not use the az - el capability.
One needed unique ground footprints and satellite tracks for each satellite, or more properly each satellite orbit type. The Oscarlocator I purchased came with ground tracks for Oscar-7 and Oscar-8. When the RS birds were launched, new ground footprints were made available, mostly through the above named magazines, which I copied on view graph transparency material at work. Others traced the new overlays onto blank transparent material.
Some of the local FM AMSAT nets provided local AOS and LOS times calculated with Oscarlocators, and I had several newcomers ask me for LOS/AOS times until they acquired their own Oscarlocator.
It is a very clever device, reducing rather lengthy orbital calculations to an almost trivial act of lining up the Oscarlocator to the equatorial crossing times in a magazine, and looking at a good clock. Of course the hard work was done in calculating the equatorial crossing parameters and generating the overlays. I continued to use it after I acquired a real time tracking program for my HP-67, but eventually transferred my satellite tracking to a computer which provided graphical output similar to the Oscarlocator.
Not sure if this is what you were looking for, but if not, feel free to ask questions. - Duffey KK6MC
On May 27, 2016, at 11:35 PM, Kevin Deane <summit496 at live.com> wrote:
> I am still interested in the way that the old timers used the Oscar Locator
> and have gotten very few responses in my past inquires... I think there was one maybe two people actually took the time and sent me in a direction they thought was clear but I might have to see it done or something. I suppose you could use keps off of any tracker and if worse came to worser you could even use months old keps and just keep track and listen...I know they do not change that much over time but enough eventually.
> My point is I would love to show my nephew how to track a sat in space with a pen and paper and two radios and two antennas ... That would be great, no cheating...Killer Boy Scout stuff right?
> Thanks for any input.
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