An Open Source 2GHz Passive Oscilloscope Probe

Electronics, like most any scientific and engineering discipline, tends to be a rabbit hole that keeps going deeper and deeper. At some point in your journey, you’ll run into the need for an oscilloscope, and in order to get the best measurements, quality probes are essential. Andrew Zonenberg is on a mission to reduce the cost of these with his open source AKL-PT1 2GHz passive oscilloscope probe.

The AKL-PT1 is a handheld 10x transmission-line probe, which is essentially a precision resistor connected to the scope through a coaxial cable. This design results in lower loading at high frequencies than a traditional resistor capacitor. The tradeoff is higher DC loading, and that you'll need an oscilloscope with 50 ohm input terminations.

According to Zonenberg, the current prototypes have performed well in testing:

• 500Ω ± 0.1% loading at DC
• Nominal insertion loss across 50Ω load: -20.5 dB
• Flat ±0.5 dB from DC to 0.91 GHz
• Flat ±1 dB from DC to 1.98 GHz
• -3 dB bandwidth of 2.19 GHz
• Rise time: 107 ps 20-80%, 161 ps 10-90%

While this isn’t the first such probe based on a resistive design, “cheaper” versions cost upwards of $300, and those that outperform the AKL-PT1 will run you over $1,000. The AKL-PT1, however, can be bought in a semi-DIY PCB option for only $20. If you’d rather not deal with purchasing/soldering components and 3D printing a plastic shell for it, a student edition is available for $150. There’s also standard and pro editions with varying levels of paperwork for pledges of $250 and $550, respectively.

More data on the AKL-PT1 can be found on Zonenberg's Kickstarter page, while its files are up on GitHub.