[time-nuts] Survey plot as art.
kb8tq at n1k.org
Sat Jan 7 17:25:30 EST 2017
There is a *lot* of difference between how various receiver architectures respond to multipath.
You can spend hours of “quality time” looking into the various claims of people having completely
eliminated muitipath by this or that software trick.
> On Jan 7, 2017, at 4:31 PM, Peter Reilley <preilley_454 at comcast.net> wrote:
> In my case (the original post) there can be no multipath difference, same antenna and done at the same time.
> The length of the cables from the amplified splitter are about the same; within inches.
> This must be some difference in the receiver, perhaps in the math?
> On 1/7/2017 4:16 PM, Bob Camp wrote:
>> In terms of multipath at GPS frequencies, a couple of inches is a *lot*. Also unless you have
>> pretty good antennas (as in much larger than 1” each) they will have phase issues unique
>> to each antenna. Phase cancellation and addition is what gives you multipath.
>>> On Jan 7, 2017, at 4:00 PM, Gary E. Miller <gem at rellim.com> wrote:
>>> Yo Bob!
>>> On Sat, 7 Jan 2017 15:16:34 -0500
>>> Bob Camp <kb8tq at n1k.org> wrote:
>>>> The “simple” answer is that the weird legs going out from the central
>>>> blob are the result of multi-path / reflections in the received
>>>> signal. With enough data you might be able to correlate them to
>>>> observed obstructions.
>>> I have lots of data from GPS with the antennas mounted 1 inch apart.
>>> They show different weird legs, so I suspect that local geology/architecture
>>> is not the whole story.
>>> For example, compare the plot I just sent, to the one attached here.
>>> Two GPS right next to each other, very differently looking plots.
>>> I'll admit to never generating plots over the same time interval, I'll
>>> start a 24 hour test of two GPS right now.
>>> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>>> gem at rellim.com Tel:+1 541 382 8588
>>> Veritas liberabit vos. -- Quid est veritas?
>>> "If you can’t measure it, you can’t improve it." - Lord Kelvin
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