The VU meter is completely software based, using IPSC Bridge/dmrlink from Cort Buffington N0MJS, Analog Bridge and USRP Audio from DVSwitch, a visual meter from Tom Hudson, Python, PHP, MySQL, Javascript, Apache, and Ubuntu.

The project started while I was traveling for work acting as net control for the PNW Digital Not-a-net (Wednesdays 1900, talkgroup Washington 2).

I built a hardware VU meter using a GD-77 and an external VU meter, but found transporting it back and forth to be tedious, and not so good for the fragile device.

Around that time, I became interested in the DVSwitch project. That never worked out, but I was fascinated that I could connect via software to a MMDVM server, and programmatically work with calls on the system. Mike N07RF approved me connecting into the system, and I started to experiment, eventually coming up with the first version of the VU Meter in February 2019. At that point, it was connecting into Suzy East which was great, except when it wasn't. Ideally, we wanted to drive traffic to VU via the C-Bridge itself, to enable selection of the traffic sent to the meter, rather than just whatever happened to be on Suzy at the time.

During Fall 2020, after a couple of webinars with Dylan KI7SBI on the original design of our MMDVM servers, and then with Albert WB7AWL on his updates to that, I learned how to connect directly into the C-Bridge, rather than through a MMDVM server.

In December 2020, the code was migrated to PNW hosting, with changes due to the difference in connection, via a direct C-Bridge connection.

Technical design: The VU meter looks at the first 15 seconds of any call passed to it, as a set of audio packets. Any packet that is below a given threshold is disgarded, in that I wanted to measure audio, not silence. I worked with Mike NO7RF to calibrate the meter to his existing metering.

While building this tool, I learned that measuring what the ear can hear can be very subjective, complex, country-specific and more terms than I thought I would need to know.

So why bother? Ultimately, what this meter does best is that it allows you to compare your own DMR audio level to others, so that your audio level will sound better to others during a net.

To better audio,
Dave/W7NCX