PVFlyer said:
gpauk said:
I had 3 PVs around lately, and measured the 5.8GHz tx out on them all..
FCC mode is supposed to be 125mW or 21dBm
The 3 I measured in FCC mode with fresh batteries (using peak hold on an avantek calibrated 20GHz spectum analyser) varied from -3dBm (!) to +15dBm. All well under spec -- and a colossal variation!
No wonder we all get different results....
Sounds almost impossible to get -3dBm. 0dBm is 1mW, -3dBm is only 0.5mW and basically no output power at all.
0.5mW ia a lot more than no power! With a decent rx (and the dji one seems to work quite well) it'll work better than you think. I work with low power microwave radio a lot.
It's be quite easy if there's an assembly error, bad soldering or failed part... I see this a lot in cheaply made rf power stages.
That unit manages about 300 feet range, despite being clearly faulty.
OI Photography said:
I'd bet that poor antenna lead connections in the Tx may to blame for a lot of that.
We connected directly to the ufl on the tx board with a phase calibrated cable to the analyser.
So the loss will be no more than the lead to dji's antenna. (mind you, ufls are pretty crap rf connectors).
I've seen reports of people flying only a couple of hundred feet and wondering why, and some managing a couple of thousand out the box. I'd expect a fair variation in tx performance from this sort of device, we see big variation in mass produced stuff that isn't end-of-line calibrated - and there's no requirement to do so with ism band stuff like there is with, say, cellular.
We'll try and fix that bad tx today, got some suitable mmics in the spares box, as the weather has gone drizzly again!