Recently I bough set of Lumenier antennas to upgrade my DJI FPV goggle. It looks quite good (except strange rattle sound when shaking stubby antenna) but I decided to perform simple measurements to compare it to stock DJI antennas.
Measuring reflected power
As you already know, professional RF measurement tools for 6GHz band cost a lot, so I build simple sweep antenna analyzer, to compare different antenna I have. It does not provide accurate(scaled) results, but it’s good enough to compare reflected power level, between two antennas, check bandwidth, etc. You can find out more about the tool there.
The theory of operation is very simply, RF generator generates signal starting from 5300MHz up to 6000MHz with 5MHz steps, which feeds measured antenna thru directional coupler. Then we can measure reflected RF power, and after applying some calibration data put everything to excel chart.
I measure every antenna 3 times, to avoid errors, and average results are like following. You can right click on the picture to view it bigger.
My conclusions are:
- Both AXII patch antennas are different. The 1st has clear resonance frequency at 5580MHz, the 2nd hasn’t, but seems to be minimum for frequencies between 5600MHz and 5760MHz. Looks like manufacture quality is not at very high level.
- The same problem with stubby antennas, the 1st has minimum at 5750Mhz, and the 2nd at 5900MHz, and it’s not so steep.
- All four lumbermen antennas have worst VSWR then DJI stock antennas, but please remember it’s not very imported …
Measuring antenna efficiency
It’s not easy to do, without RF anechoic chamber, but I tried to measure received signal using simple RF power meter. I used directional patch antenna to limit influence of reflected signals, and was trying to position every antenna to get strongest signal, without crossing the line marked on my desk.
And the results are like following.
As I wrote, it’s more funny trivia then scientific measurements, but the strongest signal was generated by Lumenier patch antenna -16,3dBm, then stock DJI antenna -21,6dBm, and then Lumenier stubby antenna -27.5dBm.
Real environment testing
Due to bad weather I had no opportunity to perform long range testing, but short range low flying testing using 25mW rf power shows that Lumenier antennas are better then stock, but hard to say how much…