Would the right approach be to use Port 0 (the source) on the VNA to drive a broadband probe (non trivial) and use Port 1 to measure the response of the antenna/LNA combination. ?You can calibrate your probe by the three cornered hat approach with 3 (notionally) similar antennas. Or choose a probe that is “known by design” (like a NIST standard gain horn or dipole).
If you’re looking for “survey” accuracies (cm or mm) there’s a lot of angle of arrival differences, although a good choke ring/artichoke antenna will have the phase center move by a mm or so over +/- 60 degree from zenith. ?UNAVCO has data on a lot of antennas on their website.
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If you check the time-nuts mailing list, there’s a fair amount of info on improvised GNSS antennas with very good multipath rejection. Probably about 10 years ago.
Time-Nuts -- Precise Time and Frequency for Amateurs ( )
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On Jan 2, 2025, at 09:33, Ted Chesley <tedchesley@...> wrote:
? Hi George, Look up "Bias Tee Power Injectors" on Amazon.Lots of them
at $15 or so with stated bandwidth to 6GHz.
-----------------------------------------From: "George"
To: [email protected]
Cc:
Sent: Thursday January 2 2025 5:11:46AM
Subject: [nanovna-users] Measuring GPS antenna bandwidth
I am building a high accuracy RTK locating system to measure my
property lines and the location of buildings on the property. To
achieve centimeter accuracy, it uses signals from multiple locating
satellite constellations on a range of frequencies between 1164 MHz
and 1610 MHz including those used for American GPS. I have several GPS
antennas, including a couple from high end Trimble survey systems but
am unsure if their frequency response extends far enough beyond GPS
frequencies and how flat the response is.
These antennas have built-in LNA's that utilize 3VDC supplied by
receivers via the coax. The antennas and the LNA's need to be tested
to ensure the system meets the bandwidth requirements. Some of them
can be broken down to access the antenna & LNA separately but I'm
unsure how to inject the necessary LNA DC power without impacting the
nanoVNA measurements.
Does anyone have recommendations for testing antennas with built-in
LNA's?
Regards,
George
Links:
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[1] /g/nanovna-users/files
[2]
/g/nanovna-users/leave/12583772/4866111/1865567994/xyzzy
