RF module for spectrum?

[erhard52]

Erhard,

I do not have any real lab equipment to measure the output of the transmitters.  I tried using an Immersion RC Power Meter, but since the transmitter signal is hopping and has a low average power, I could only get vague results.

However, I did get repeatable results using the XPS XDP device in conjunction with the XPS RSSI application.

I have repeated this test with my XPS JR and XPS Futaba transmitter modules and the results were pretty much the same.  Using the XDP device:

Bring up the Tx RSSI tester application and place the working transmitter 3 feet away.  I just did this test with my Taranis and XPS-J1 transmitter module.  At 3 feet I saw signal strength numbers in the area of -40dBm.



Then I moved the transmitter to a spot about 20 feet away and the new RSSI numbers were about -61dBm.



Then, still about twenty feet away, I placed the transmitter in my refrigerator (a big metal box) and the RSSI went down to -77dBm.

Since both of my transmitter modules produced similar results, I decided that they were both working properly.

The RSSI numbers can vary quite a bit based on the relative location of the transmitter and the XDP device.  I wasn't so concerned about the absolute numbers.  The test can, however, give a good comparative results to see if one transmitter module is performing differently from another.

Paul

p.s.  With the RSSI application running, you can press the low power button (range check mode) on the back of the transmitter module and see the overall signal strength go down.

thanks Paul
yes i remember you shared that data with me earlier and i also repeated it need to look up my numbers again - or better remeasure.

adding:
when i flew today repositioned the receiver antenna - the ends are already on top of the wing, one parallel to the fuselage and one perpendicular - now i basically turned this setup by 45 degrees. so now both antenna parts are about same distance from the conductive (carbon) fuselage. i also pointed the transmitter antenna 45 degrees down to the ground instead usually i have it point basically to my chest. this all did not make a difference -

one thing is not ideal with the LQI. if the number is not changing it is not clear if there was no update or the number was the same because for at least 30 sec it was fixed on 80%.
anyways so far i have not noticed any dropouts