Thursday, November 24, 2016

Low Power Devices on 433 MHz

At the moment, I scan the 70cms band on a pretty regular basis and every so often, the radio will stop on  433.475 and 433.525 MHz. The signal sounds like a weak digital transmission and it's only there occasionally.

I thought perhaps it was due to an out of band signal and the receiver was being overloaded. Having said that, the Alinco 605E seems like a reasonable radio and the front end doesn't seem to be wide open like some of the handhelds.

After a bit of digging, I discovered that there is an allocation for low power device on the 70cms band. It's called LPD433...

This is the frequency chart which as you can see goes from 433 to 435 MHz.

I knew that some car key fobs and remote devices were using the band but I hadn't realised it was so extensive. Perhaps that is the reason behind the mystery signals?

What I didn't know was that in Europe, this allows licence free voice communications on 70cms.

"LPD hand-held radios are authorized for license-free voice communications use in most of Europe using analog frequency modulation (FM) as part of short range device regulations, with 25 kHz channel spacing, for a total of 69 channels."...from Wikipedia.

I noticed that Amazon are selling a dual 446 / 433 MHz radio as well...

Considering how easy it is to buy a radio, I wonder will there be more unlicenced operation on the 70cms band in future?

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