sudden dive

[erhard52]

Erhard,

When you get that XDP device, you can also use it to run the XPS "RSSI" application that comes with the suite of XDP programs.  The RSSI application displays in real time the signal strength received by the XDP device.  I performed the following experiment to compare the output of one my transmitters when I had a concern about its output.

Connect the XDP device to a PC and activate the XPS “RSSI” application.



Then put the transmitter module into binding mode.  Then click the button on the RSSI application and follow the instructions provided by the application.  After it connects to the transmitter, the RSSI application displays the number of channels, the frame rate, the channel hopping mode and the RSSI as received from the transmitter.



Be careful to keep the transmitters and their antennas and the XDP device in the same locations during the testing.

Measured on the bench, my Futaba 9C, Taranis and Jumper T12 transmitters and their respective XPS Futaba and XPS JR-type modules all delivered -36dB to the RSSI application as the strongest signal.  When I moved the transmitters to the next room behind one wall and the refrigerator, the RSSI decreased to -57dB for all three.  When I put them inside the refrigerator (a steel box), the RSSI decreased to -77dB for all three.

Since all three transmitters gave similar results, I reckoned that all three transmitter modules were transmitting as designed.  If you see a significant difference with your equipment, then you may have found something.

Out of curiosity I pressed the low-power button (range test) on the transmitter modules and observed that the signal strength went down by about 25 dB.

Paul

Paul thanks so much for the  tip. i will follow your advice - XDP should arrive early next week. i will keep you posted. if you have any hint on how to better use the tinySA for the purpose i would also be curious. so far the highest output i see is in the DSM2 module which does only use 2 frequencies. i wonder if the RBW on the SA impacts my measurement?
btw.: i assume all your dB are dBm right?
here again my link
https://1drv.ms/w/c/9dc6d60a8cb4c333/EYo...Q?e=axodOF.

it was funny that after i did my direct power measurement on the DX6i, when i i went back to flying i realized the connection took longer and the motion on the rudders had a bout 1 sec delay. so turned off/on did range test and all looked normal but when i flew i also had a drop out. luckily landed in high grass. - today all was normal during flying. weird.
once i am confident with the XCPS system i will use my evo12/XPS again and probably RFU instead of NANO

I am unable to comment on the Tiny SA measurements as I have no experience with that device.  In fact, the I used the RSSI measurements from the XDP only to compare several radios - I didn't know what the actual RF power output values were.

Yes, dBm.  Also, I believe that the DX6i's label of 17.93 dBm on the RF board is accurate.  Add the gain from the antenna and it's very close to the legal 20 dBm limit.

Your observation of slow-responding controls is mysterious, but it doesn't sound like an RF problem.  Power maybe?  Or someone is jamming the 2.4GHz band at your flying site?

regarding output  power i assumed that it is the total rf power emitted without antenna gain but who knows. 
on the interference you are right , i had the same thought about strong interference or almost as you state like broadband jamming. it was moving like in slow motion. or i was in a time warp somehow.
strange to have to deal with these things. i thought that problem was left behind 40 years ago before FHSS