Got ~10x Surveilzone (Foxeer) VTX’es around, from 25mW to 600mW, also 25/200mW Aomway and decided to check what’s inside.

Testing setup – RFE + attenuator chain. 60dB attenuation + 3dB offset in RFE, so in total you need to add ~63dB to visible averaged result on graph. All tests done on C1 channel (5705MHz).

Absolute power ouput is not precise, relative – much better (0.5dBm or better).

Cold testing – ~10s after powering on (already full averaged cycle), hot – after 5 minutes on my desk.

This looks like:

VTX’es From low to high:

• SZ 25mW:
  Physically smaller than 200/600mW versions. No issues with heat – only warm after 10min on desk.Tested two. First one was perfect – ~35mW output and very stable. Cold:Hot:

  

  Also, video with this VTX, range test from ~2:00:

  Second one wasn’t so good. ~20mW output and, what’s worse – frequency is offset by 5MHz – also the same issue on another VTX.

  Cold:

  

  Hot:

  

• SZ 200mW VTX:Uses TM6659 as power amplifier, bigger than 25mW version, becomes hot after some time (but still can hold in hand, so < 60°C for sure):Tested two of them, first one (better) ~600mW output when cold (way higher power output, datasheet says that typical power output is 22dBm):

  

  ….and ~180mW when hot:

  

  Another one does not work so great. Cold is approx 200mW:

  

  Hot is only ~40mW, but while low power is issue, much worse is frequency shift. Peak is at 5700, instead of 5705MHz.

  I did not tested other frequencies, but this issue is also seen on 25mW version, i guess, there’s something wrong with frequency selector on both VTX’es….

  

• SZ 600mW VTX:Physically the same size as 200mW version, weight is the same. Uses TM6599 as power amplifier, so output peak should be around 800mW. Becomes really hot after some time, requires cooling:Tested only one (have 4, but all perform +/- at the same level, except one which has “jumping power output” and is unusable). Cold is ~150mW:

  Hot is ~100mW:

  

  (and no, i did not powered it without antenna, this one is brand new from package, but others perform +/- at the same level).

• Aomway 25/200mW:Somewhere between SZ 200mW and SZ 25mW by size and weight. Has jumper for 25mW power output, but i did not tested it, only “stock” 200mW. Becomes extremely hot on desk, impossible to touch case, possible to touch SMA connector, but not handle – requires cooling for sure.Cold is ~250mW (i guess, it’s the same “rebranded” 250mW Aomway VTX, after all), but again, frequency sometimes shifts (have in mind – C1 on other VTX’es is A1 here (5705MHz)):

  Hot (should i say “extremely hot”?) is around 100mW:

  

Summary or TL;DR version:

Not impressed at all. Really.

25mW VTX can be really good, nice range, low weight, small, etc – but second one does not perform so good. I will re-test it at different band if i find time, maybe this issue with freq shift is only for C (ex. “Boscam”) band?

200mW VTX performs really great – nice power output, small enough and does not heats much. But again, inconsistent.

Also, some physical issues with them – SMA middle pin is soldered to very, very small PCB patch, so even small force on SMA can develop cracks in this connection and then you will have more issues.

Another thing – they recalled all VTX’es and “fixed” them some time ago (they could change freq. while flying, one time is enough =)

Fix is…. Add some paper inside:

Yes, paper. Not kapton tape, not proper conformal coating, but paper… Meh.

600mW version is complete mess – low power output, poor quality control, heats a lot – avoid.

Aomway… Not sure what to say…. Needs more testing on different frequencies/bands and with jumper set.

So far, keep only 25mW and go pick another powerfull VTX if you need ;-)