[time-nuts] eBay GPS antenna test results.
jimlux at earthlink.net
Thu Feb 15 09:13:25 EST 2018
On 2/15/18 6:04 AM, Bob kb8tq wrote:
> There are a number of reasons to believe that these antennas are worse
> than the typical “telecom GPS” antenna for L1 only duty driving a TBolt.
> If you are going to do L1 / L2 work with something like a NetRS, then indeed
> you will need a dual band antenna. These (the $99 ones) are the lowest cost
> “new in box” L1 / L2 antennas that I have seen. One would *guess* that their
> close to horizon multi path rejection is not quite as good as a Trimble Zephyr,
> a Novatel Pinwheel, or a choke ring. The ones from China
> also don’t cost $1800 to $6000 when new either …
one could probably improvise something that serves as a choke ring, or
elevation fence. The infamous JPL Helibowl is pretty simple, and has
pretty good rejection of signals near the horizon.
See, e.g. Page 143 in GPS/GNSS Antennas, by Rao. (I found it on google
Oddly, it cites to C.Y Cheng, Numerical Electromagnetic Modeling of a
Small Aperture Helical-Fed Reflector Antenna, Masters thesis, Ohio
University, Aug 1998.
Good luck finding that one on-line
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