FAQs

Q: What is the difference between channel steps and channel bandwidth?

A: Let’s look at channel bandwidth first:

Wood & Douglas manufacture radio telemetry modules with 12.5kHz, 20kHz and 25kHz channel bandwidth. So what’s the difference? Well, consider first a radio transmission with no signalling on it – an unmodulated carrier. It occupies a very narrow bandwidth.

When our radio module transmitter is fed with a signal to transmit, the radio module frequency modulates the carrier spreading the energy over a very carefully defined bandwidth.

Channel bandwidth is set by the radio licencing authorities in your country and we have different build versions when we make the modules in our factory.

Wider bandwidths, if you are allowed to use them, are desirable if you want to squeeze more information across the radio channel. For example the W&D ORION radio modem can send 9600bps in a 12.5kHz radio channel. The 25kHz version has an over-air data rate of 19200bps!

Next we will look at channel steps:

Channel steps set the possible centre frequency increments. Typical numbers are 6.25kHz, 12.5kHz and 25kHz and are part of the factory build and configuration. In the diagram below, the channels can be programmed with 6.25kHz increments, e.g. 455.0000MHz, 455.00625MHz or in the case of the first channel shown, 455.01250MHz. The second channel has been programmed with a centre frequency of 455.04375MHz. 

Sometimes the term channel raster is used to indicate programmable centre frequency step sizes.

When placing an order with us, we will ask you for your desired operating channel (centre) frequencies and the channel bandwidth. This is to ensure that we manufacture the correct version of our modules for your application.

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