Tag Archives: measurement

VTX power comparison – quick run #3


Got several new 5.8G VTX’es and decided to test their power output. Quick table for reference, but see notes below:

VTX dBm mW Comments
Aomway #1 (fat pigtail)
8 6,3
22 158,5
Aomway #2 (thin pigtail)
5 3,2
24 251,2
Aomway 4″ copter
-13 0,1 Dead PA…
-15 0 Dead PA
RP-SMA DIP BG: http://www.banggood.com/Skyzone-FPV-TS5813S-5_8G-25mW-40CH-Mini-AV-Wireless-Transmitter-For-Mini-Multicopter-QAV250-p-1021364.html
10 10
Foxeer 600mW:
23 199,5
Foxeer 200mW:
24 251,2
Foxeer switcher:
11 12,6 (floating – pwr1)
13 20 (floating – pwr2)
13 20 (floating – pwr3)
600mW: http://www.surveilzone.com/58G-32CH-AV-600mW-Mini-VTx-for-DJImini-Multirotor-g-1303
26 398,1
TS58400: http://www.banggood.com/Skyzone-TS58400-5_8G-400mW-32CH-AV-Transmitter-Module-p-1004170.html
24,5 281,8 (stable)
ET526: http://www.banggood.com/Eachine-ET526-5_8G-40CH-25mW200mW600mW-Switchable-FPV-Transmitter-p-1075702.html
13 20
22 158,5
26,5 446,7 Hot
FT48X: http://www.himodel.com/FPV_Telemetry/FPV_5.8G_0.25-600mW_Adjustable_48-Channel_A_V_Transmitter_VTX_FT48X.html
13 20 (stable)
21 125,9 (stable)
25,5 354,8 (stable, veryhot)
-5 0,3

In short:

  • My equipment is not calibrated for absolute power output, but is precise enough (~1dB) for relative power output. Have that in mind when comparing power output between different measurements.
    In other words – relative output between VTX’es is precise. Exact power (for example, 300mW) may be off (may be somewhere in 3dB range).
  • All measurements done at A1 channel (5865MHz), 2 minutes after powering up, stock heatsinks and no airflow; 20x 1-second sweep iterations, max power average
  • Third switchable (25/200mW) Aomway which dies in the same way. No, it was not powered without antenna. Sometimes PA just dies for some reason and it becomes unusable (module is sold on taobao, but not on public-accessible places, so… Expensive and useless)
  • Foxeer 600mW sucks, but nothing new (see earlier post about it)
  • Foxeer switcher is useless – switching maybe internal heat generator, but not power output. But note – i have first version, with SMA on side. Second version (SMA in middle) may work better (and yes, i unpowered/powered it back after changing power setting). Also, it’s power is jumping in +/-6dBm range all time, really random-power VTX
  • TS58400 is something i like for mid-range mini-airplanes. It’s compact, no excessive heating (but i’m using small heatsinks on 2 of them), has very stable power output (all other VTX’es change power with time due to heating) and very stable frequency. Too much power for race copters, but nice stuff for mid range
  • ET526 is nice, starts-up at zero power, need to press button to power up. Heats up a lot at max power setting, airflow required (or at least heatsink). Two buttons for configuration and strange channel layout (A1 == C1 here, etc)
  • FT48X – VTX with 5.3G band! Startup at 25mW, which may be good and bad at the same time, depends ;-) Two minor issues with it – very hot at max power (the same as ET526) and “no RF power setting” is actually “Low RF power”, which is still flyable few meters around (~15m range with omni antennas), so you MAY kill someone on race with that “no power mode”. Other than this… Nice VTX with mic.

Simple portable RF power meter

I had several RF heads – based on AD8317 (and working from PC), also based on AD8313 (you can get entire RF head assembled for ~20$ or so at https://www.sv1afn.com/projects.html) and decided that i need portable box for measuring signal levels and VTX power.

Did that, working well:

it’s actually very simple and entire box costs ~35$ or so (if you have basic parts and attenuators already). Accuracy is acceptable (+/- 1.5dBm in -10 … -40dBm range).

And no, it won’t work better than other tools (even RF explorer is much better with it’s -105dB+ range); it won’t do correct math for frequency (MCU is too weak to do proper calculations). So, if you need serious tool – go look for other solutions. If you need something cheap and working well enough to test antennas/TX/RX – it works good enough.

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