Hi guys,
Do I see some panic?....please don't!
There could be many reasons for the RIGOL readings ( although 48mV is quite good if many preipherals connected ):
1. USB ground pushes a lot of noise from the PC;
2. Almost most of the telemetry modules generate a lot of noise;
3. Poor ground loops can lead to the same.
So, to investigate the situation I suggest the following:
1. Show me your wiring, but exactly as it was during measurements;
2. Disconnect the USB and measure again, but push MEASURE button to see the measured Vp-p;
3. Perform the same measurements over the 3V3 of the GPS module;
4. Disconnect the noisy peripherals such as OSD, Telemetry and Video Tx and measure again.
About redundancy ( if you really really need it ), you'd better use some good 6V BEC over one of the servo outputs. You can use it simultaneously with your Power Brick....no problem. There are 2 x 2A Schottky ORing diodes which make this possible. Thus just the higher voltage supply will work, while the other will be the redundancy one. If the lower supply fail, the other will take care of the system without noticeable switching.
If you have any other worries, please ask here or on private.
Best regards
Nick