Winter 2006 Issue

Diversity Reception
for Amateur Radio


WB9YBM discusses a “diverse” way
of receiving amateur radio signals.

By Klaus Spies, WB9YBM

 

Although diversity reception has been used for well over a decade in the commercial side of radio communication, it has been under-utilized (if utilized at all) in amateur radio. One reason may be due to the expense involved with the receivers, as a diversity receiver has two RF and IF stages, instead of just one each, which is typical of common receivers.

For those who are new to the concept of diversity reception, here is a brief explanation: The “diverse” part of “diversity reception” is a diverse antenna location. Instead of using the typical single antenna to receive a signal, two are used. They are spaced one wavelength apart, so that if propagation characteristics or signal-path changes from mobiles occur, signals will fade in at one antenna, while signals fade out at the other antenna. This way, a signal can still be heard. Making certain identical antennas, coax types and lengths, and receivers are used will ensure a fair and equitable chance that the signal will be received with the same chance at either antenna.

Here’s how diversity reception can be realized in amateur radio without the need for expensive, specialized receiver equipment. In this example, the receivers available on your ham shack bench can be used—without even requiring modification!

Especially on the VHF and UHF bands, we’ve all noticed how signals swish-swish through signal nulls either when we ourselves are mobile and listening to our favorite repeater, or when we’re trying to work mobile stations on simplex. In extreme cases, we’ve even lost a signal entirely, only to regain it by rolling our cars forward or back by a few feet.

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