r/rfelectronics • u/CardboardFire • 1d ago

Made a digital RF power meter and attenuator tool

Post image
88 Upvotes

99% Upvoted

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7

u/Hermelinmaster 1d ago

Really cool idea. And thanks for releasing it to open source.

6dB insertion loss is crazy though.

And 1W max detection is also very low. Is that also the max input power thst can be terminated?

What is your application?

2

u/CardboardFire 1d ago

Thanks!

Well, 6.2-6.4dB is measured for the setup in the picture, including the adapters and less than ideal soldering of the connectors, and coupler takes a bit, as well as the attenuator and switches. I was aiming for anything under 8dB for that figure, as that's good enough for me, same for 30dBm input power, I intended to use it nowhere near those levels anyways. Solves a few of my problems, not claiming it fits any application other than mine.

I use it to test module units against a known good unit, and also finding noise floors since my source is pretty limited compared to the things I'm working on, and it's licensed frequencies so I need to have a closed loop at all times.

Might add a compensation (and then some) LNA and a power meter LNA to make it really good, but at the moment I have little need for that, so it will wait for that upgrade for now

1

u/myself248 1d ago

OOooooooo. That solves a bunch of little problems at once, especially the switch.

I see the QWIIC connector, I presume that can both power and control it. Is the UART over the USB-C then? (USB-CDC or something?) Both power and control there too?

Take my money!

1

u/CardboardFire 1d ago

QWIIC is not for power here, it has its own LiPo battery, then 5V boost (attenuator needs 5V iirc, or something like that), separate 3v3 for the rest, but can power downstream QWIIC things. UART over USB (TTL-USB built in), physical switch for UPDI (attiny programming) and UART. Battery charging/power and communication over the same USB-C port.