He’s using an everyday LED as a detector diode and an internal pull-up resistor in the ATtiny13 for the bias voltage. The antenna runs off the LED’s anode.

This simple circuit helps you sniff out RF radiation leaking from your transmitter, improper joints, a broken cable or equipment with poor RF shielding. The tester is designed for the 2-m amateur ...

National Semiconductor Corp. has introduced the industry’s first radio frequency (RF) power detector to offer guaranteed accuracy over temperature, and RF production testing, for third-generation (3G) ...

To address the challenge of improving power-added efficiency (PAE) for high-powered amplifiers, Analog Devices developed the ADL5511 TruPwr rms and envelope detector. The chip combines two RF ...

Measuring RF power and return loss in radio or test-and-measurement applications typically involves the use of directional couplers and RF power detectors. This solution combines the two.

The LMV221 RF power detector from National Semiconductor Corp., Santa Clara, Calif., targets mobile-phone power controls in current and emerging cellular standards, including ...

It’s not so far-fetched though, while bugs and hidden cameras in for example an Airbnb may not have flashing LEDs, they still emit RF and can be detected with a signal strength meter.