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[Lyle Williams]

This is a bit of a cross-post from the lighting forum.  I've recently got a lot of the little cheap wireless DMX pcbs, and found them to work very well.  They interoperate with a bunch of other cheap 2.4G wireless DMX units, so it seems many of these units are doing the same thing, modulation and frequency-wise.

The little wireless DMX boards transmit at 2400MHz regardless of what "channel" is set.  This means that the channel changes the modulation, rather than shifts transmissions to grossly different frequencies. The marketting blurb in these is not particularly clear in on technical details, but it seems they use GFSK modulation on 126 frequencies with FHSS (frequency hopping spread spectrum).  126 frequencies would give them the seven different sequences to make seven channels, so I'm guessing that's how they work.

Transmission at 2400MHz means that you should stay clear of WLAN channels 1&2 if you are picking a wifi channel and running wireless dmx.

If you are running 40MHz wide channels, then stay clear of channel 3 aka 1+5.

[Lyle Williams]

The pcbs I have use a STC microcontroller and a nRF24L01+ chip as the transceiver.  This is a 0dBm TX, -93dBm RX part, and there apears to be a RF amplifier following it.

[Scott Holtzman]

The pcbs I have use a STC microcontroller and a nRF24L01+ chip as the transceiver.  This is a 0dBm TX, -93dBm RX part, and there apears to be a RF amplifier following it.

That explains why they live so well with wife.  While the ISM band maybe within the wifi range it doesn't fall on a channel pair.  Also just because it's ISM people think wifi.  This is not a wifi radio.


It uses it's own modulation standard and in 1Mbps rate mode (which) I am sure they used has excellent error checking and fault tolerance.  With the channel spacing it uses 126 channels and the RX side is a a rake receiver (multiple RX's, kind of an on board voting setup) and the CRC can be used to discard to RX's with bad data.  It's a clever part.

[Lyle Williams]

I think they are awesome, but I wouldn't use them for U2's next world tour.  The nRF24L01+ is marketted for a range of lower-cost applications, unintentional interference is possible.  Intentional interference would also be quite easy - just buy a dongle, a dmx controller, and sit closer to the lights that the real transmitter.

Also, some emissions appear to fall slightly below 2400MHz.  Probably a rookie mistake by the original implementer, and everyone else has had to copy to maintain compatibility.

[Scott Holtzman]

I think they are awesome, but I wouldn't use them for U2's next world tour.  The nRF24L01+ is marketted for a range of lower-cost applications, unintentional interference is possible.  Intentional interference would also be quite easy - just buy a dongle, a dmx controller, and sit closer to the lights that the real transmitter.

Also, some emissions appear to fall slightly below 2400MHz.  Probably a rookie mistake by the original implementer, and everyone else has had to copy to maintain compatibility.

It also appears you can jumper off the transmit function.  I need to look at one of the boards and see if there is a solder land to that pin on the package.

[ProSoundWeb Community]