On 04/18/2013 04:00 PM, Jim Lux wrote:
On 4/18/13 12:01 AM, Chris Albertson wrote:
If I read the paper correctly you can skip the choke ring if you mount
the
antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot
lengths. The choke ring is for portable survey antenna that can't be
placed on tall rooftop masts. I think a 2 meter pole on a roof pretty
much meets their criteria of multi path difference being over 10 meters.
yes.. multipath that is more than a chip away is generally filtered out
by the PN tracking loop, so all you really worry about is multipath
signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300
meters long. If you're doing P/Y code, it's a tenth of that.
In reality, if the multipath signal is lower, and it's "far" away (a
good fraction of a chip) it doesn't contribute much to the output of the
correlator. So their 10 meter thing is probably a good number for a
"typical" receiver they make.
It's an interesting mix of sample-rate/bandwidth, code you track and
distance between early-late detectors (normal distance is one chip)
comes in when analyzing and combat the multi-path. I recall there is
some subtle points with some of the C/A codes.
Cheers,
Magnus
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