[time-nuts] GPS backup for the stationary time and frequencyuser
jimlux at earthlink.net
Fri Oct 8 18:22:43 UTC 2010
Brooke Clarke wrote:
> Hi Jim:
> I've got a spare Ku band satellite dish and would like to use it for GPS.
> In an ideal application the GPS antenna would be mounted in the normal
> manner and above it would be a sub-reflector aimed at the Ku dish.
> That way the antenna might pickup sats near the horizon directly and
> from a narrow part of the sky by means of the dish.
> The dish might be aimed at a WAAS GPS sat.
> I've heard that you can just use the TV dish with a normal GPS antenna,
> and it gas gain even though the polarization is reversed.
Give it a shot. The other thing is that if you have your GPS antenna
facing straight up, at the focus of the dish, you're looking at the side
of the gps antenna, where the polarization might be less circular.
But one thing to think about here... a standard Ku dish isn't very big..
At GPS frequencies, you're looking at 20 cm wavelength. The dish is
perhaps 2, maybe 3 wavelengths across. That's not a huge amount of gain.
You might do just as well with a flat cookie sheet.
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