Amateur Radio Diversity Reception Post Processing

Hey all,

I am experimenting with “diversity reception” in Amateur Radio… Diversity Reception is recording the same frequency and mode using two different antennas and receivers. Each source is mono then joined together as a left and right channel. Your “brain” can better isolate the weak signal from the noise…

I would like to try some Audacity tools/programs against either the combined stereo recording or the two individual mono channels and logical “AND” to create a new mono channel in an attempt to minimize the static each channel contains. I am new to audacity and wanted to know if there was a tool or program out of the box that could achieve this?

Happy to accept any other “recipes” that you may think will make a difference.

Thank you!

Regards Dwayne

Each source is mono then joined together as a left and right channel. Your “brain” can better isolate the weak signal from the noise…

Have you tried that? That would give me a headache or upset tummy in about five minutes.

When you experience a surround video or movie, the spoken dialog is almost always presented from dead center—Center Track in Dolby. Nobody can deal with the point of interest shifting constantly during the show. Stereo FM tried that, too when it was new. The announcer was in stereo with two microphones and that lasted about a week. The announcer is always in mono—dead center

We could help you out a lot if the radio signal went to silence or low volume during the transmission failure, but it doesn’t, does it? It just dissolves to hiss or trash depending on the radio system. I don’t know of any Audacity tools or filters that “know” what a voice is. It’s all just wavy blue lines that don’t change all that much when the transmission collapses.

I can think of a way to do it if you can program and have a lot of time on your hands. Recognize the broadband pink or white noise when the transmission fails and switch. You would have to double the volume of the one that was left so not to get a volume bump during the correction. Also tailor the delays and clip points so as not to get pops and squelch tails on everything.

And then decide what happens when they both die at once.

You would have to do this in post production, not real time. Do you know Nyquist or C++?


You should be able to get acceptable sound by setting the squelch on each radio, and then just jam the two sound lines together. We can help there. There are tools to auto set voice volume and I’ll find them any minute now. That will get rid of the 6dB (half and double) during the squelch.

No programming needed and no headaches.

Nobody can help you if they both go together.


There it is. LevelSpeech.

That, the squelch adjustment and mono mix should be all you need.


Yes! It’s actually a feature of one of the Software Defined Radios I have - The Flex Radio 6600. I wanted to “AND” the left and right channel since they are each from separate sources and possibly the noise is unique to each channel but the signal is common. If I can find the right combination of post processing that works well to isolate the weak signal from the static, I can submit back to the developers and they ideally could make it an option in their app.

There may be a problem.

If the noise is the same in both left and right channels, then that would be a center panned mono signal across the two stereo channels. If I’m understanding your description correctly, the audio signal that you want is either panned hard left (left channel only) or hard right (right channel only), so the audio that you want can be considered to be “true stereo” as no part of it is common to both channels. Isolating the audio that you want to retain can then be done by a logical “XOR” based on phase and frequency (which can be done with FFT). This is available in the “Remove Center” option of the “Vocal Reduction and Isolation” effect: Vocal Reduction and Isolation - Audacity Manual

On the other hand, if the noise in the left channel is independent from the noise in the right channel (“uncorrelated”), then the noise is also “true stereo” and there is no logical operator that can separate the noise from the audio (both the noise and the audio are dissimilar in left and right channels).

Thanks! With separate sources for left and right channels I am cautiously optimistic the noise will be unique for each channel but the signal I am trying to isolate will be common.