How to prevent oscilloscope probe failure when measuring radio transmitter output power

While setting up a homemade radio transmitter with an output power of about 4-5 watts, I encountered a failure of the oscilloscope probe. On the oscilloscope screen, I observed a decreasing signal amplitude, and then the signal disappeared, and the smell of burnt electronics emanated from the oscilloscope connector. What happened?

I have another similar probe, called the 6100. These probes have a frequency divider of 1 and 10. If you measure the transmitter's output power using a divider set to 1 and then to 10, you'll see that the current drawn by the transmitter from the power source will change, and, accordingly, the signal amplitude will change, which, in turn, leads to incorrect measurements.

The oscilloscope probe failed because I didn't set the probe divider to 10. The description for the probe and the oscilloscope says that when measuring signals above 5 MHz, you need to set the divider to 10, which I didn't do. I decided to disassemble the probe to see what burned out.

You can see this burnt component in the connector. It's possible it's a burnt resistor. This component clearly absorbed some of the transmitter's power and became very hot.

I also disassembled the other part of the probe

There's a switch for 1 and 10, three resistors of 240 ohms (first), 4.3 megohms (second), and 4.7 megohms (third), and a 17 pF capacitor. It turns out that without switching the divider to 10 on the probe, some of the transmitter's power was being fed to the components in the connector.

Conclusion. When measuring the output power of a radio transmitter with an oscilloscope, be sure to set the divider on the probe to 10, even if it's 1 watt of high-frequency power. Otherwise, the oscilloscope probe will  the radio transmitter to malfunction and distort the measurements. If you're measuring high voltage, you should also set the divider to 10.