5.8GHz transmitter only transmit when logic analyzer probes are connect

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Ben_Tan

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Hi:

I have implemented a 5.8GHz transmitter to communicate with a Drone using Teensy 3.6 via SPI connection with 2 MHz clock.

I notice a peculiar observation, the transmitter only works when I connect probes of the logic analyser (Saleae) to the SPI lines (MOSI,MISO, CLK etc)
There is suggestion to terminate the SPI lines and I read up on RC filter on high speed transmission line. Any suggestion? Do I need to have the LPF on all the lines? Any loading the Teensy?
 
Maybe a ground wire is missing?

This is a common scenario, where a project only works with an oscilloscope is connected because the scope is connected to ground and completes a required ground connection.
 
Maybe a ground wire is missing?

This is a common scenario, where a project only works with an oscilloscope is connected because the scope is connected to ground and completes a required ground connection.

Nope. The Teensy ground is connected to the transmitter and analyzer probe ground is also connected to it. The Teensy is powered via USB.
I notice the overshoot in the CLK and MOSI is damped when the probe is connected.

I used to notice on Teensy 3.6 that it occasionally works when I use the different GND port on the Teensy
 
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