Purchased for $45 from Amazon here on February 8, 2022
This antenna was given a full 3D spherical swept gain test program with gain measured in over 400 physical directions and at 200 frequencies. This kind of testing helps you visualize the full radiation sphere. With normal intended installation the antenna would be vertical (the Z axis in these diagrams) with intended gain towards the horizon (from the sides of the antenna) in the XY plane.
When marketed as a 10 dBi antenna, one would expect the gain in the “sideways” directions to be approximately 10 dBi. (This is way too good to be true – at a glace we can tell that this antenna is physically too small to possibly have omni-directional sideways gains of 10 dBi.) Actual measured sideways gain was as follows: 902 MHz -0.7 dBi; 915 MHz -1.1 dBi; 928 MHz -1.4 dBi.
While a peak gain of +2.6 dBi was measured, it was about 30 degrees above the horizon, and not really very useful. So this antenna is falling far short of the expected sideways gain/directivity by a whopping 11 dB. It is typical of consumer antennas to have over stated gains, so these results are not surprising. Although this is a fairly egregious over-statement of gain!
Upon disassembly, it can be seen that the antenna topology is a simple conical skirt monopole, which would normal have a sideways gain of 2 to 3 dBi. The 0.200″ diameter coaxial cable had a loss of 1.1 dB at 915 MHz.
The images below are all click-to-enlarge.