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Diversity Reception Primer – Improving Radio Reception

diversity reception primer

It started nearly a century ago, with efforts to reduce the effects of multipath fading. Here’s the complete diversity reception primer.

Recently, I was asked to produce a diversity reception primer for our Saturday morning Cycle 25 meet. I did, and you can watch my diversity reception primer here. Now for a quick summary.

Multi-path fading was a big problem in the early days of radio, and today as well. Signals take multiple paths to arrive at your antenna, You will find each path to be longer or shorter than another. You also know that when signals arrive 180 out of phase, they try to cancel each other. That, my friends, is multi-path fading.

Back in 1926, Harold Beverage figured out that if you used two or three receivers each with a separate, spaced antenna and combined the results together, the probability of a better signal to noise ratio increased significantly. They call this diversity gain.

At the same time, when you combine signals from two or three antennas, you have an antenna array. You get array gain by creating lobes and nulls of multiple antennas working together. You can do diversity with multiple signal chains before the receivers (analog) or inside digital receiver at baseband. By multiplying data from each receiver by matrix math which balances amplitude and phase of the signals you can achieve beam steering.

Finally, you can cancel interference by shifting phase and amplitude of signals and noise so that they cancel each other. Think of noise cancelling headphones. These three factors – diversity gain, array gain and interference cancelling – make up modern diversity reception.

Diversity Reception Primer on Ham Radio Workbench

On October 19th, I joined the gang on Ham Radio Workbench podcast for an extended diversity reception primer with questions and discussion. If you are into ham radio building and experimenting, you will really enjoy this podcast, which comes out every two weeks. You can listen to our discussion here.

I think the Cycle 25 video and HRWB episode do a good job of summarizing what I have learned about diversity reception over the past few years. The podcast in particular does a dep dive into the capabilities of modern ham gear and how easy it might be for manufacturers to offer this feature to more radio hobbyists.

In the meantime, I have probably gone as far as I can with my resources and realities to lean into diversity reception. Now it’s just time to enjoy it.

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