Maplin Forum discussions on 433.92MHz interference

[sfws]

http://forum.maplin.co.uk/viewtopic.php?f=20&t=1710
Readers might find this recent discussion of interference between Fine Offset 433.92MHz models, wireless door bells and wireless Central Heating thermostats interesting.

[mcrossley]

As a bit more background, my understanding so far is that for 433MHz units...

The transmitter seems to generate a random 'id' each time it is power cycled.
The transmission is OOK.
Each data burst has a CRC.
Each data burst is transmitted twice (some units may be transmitting three times).

The 868MHz units seem to be different in that they may be using FSK rather than OOK - jury is still out, but I cannot pick up any data from mine using an OOK receiver.

[AllyCat]

The transmitter seems to generate a random 'id' each time it is power cycled.

Hi,

My belief is that there is no "address" data in the transmissions, the device's "signature" is only defined by its exact point in time. The transmitter bursts are exactly 48 seconds apart and the receiver wakes up (or listens) only for short periods at this repetion rate (to reduce battery power consumption) and assumes that any transmission is from the correct transmitter.

Beware of generalisatons about the "Maplin protocol", because there appear to be two, one up to about a year ago and now a "new" one. These appear to be very significantly different (maybe even one using OOK and the other FSK) with different data rates, probably error checking (or lack of), and number of message repetitions, etc.. The "new" Maplin protocol has been reported on this forum (using a Raspberry Pi), but appears to be different to all three FO units that I have examined (434MHz 1081 and 3080 and 868MHz 1080), also all different to each other.

Cheers, Alan.

[mcrossley]

Agreed, you might think FO seem to bung in whatever RF units they can get hold of cheapest for each batch and alter the design accordingly!

[john6174@outlook.com]

I have a WH1080 and a WS 3083. The WH 1080 has finally died after about 10 years but the receiver and display is fine. How can I change the WH 1080 receiver to move from 866.3 MHz to operate at 433.92 MHz to see the WS 3080 weather instruments?

[AllyCat]

Hi,

Welcome to the forum. If your WH1080 is around 10 years old and 868 MHz, then it may well use the "old" integrated FSK chipset which is totally incompatible with the later OOK protocol (and IMHO not "hackable"). IIRC, Clas Ohlson were still selling this format in around 2013-14. Of course the 1080 Console could not receive or display the "Solar" (Pod) data from the 3083 transmitter.

Take a look at the two sticky threads at the top of this Fine Offset section of the forum, to see how their "enclosures" can be opened, and the various versions of their inside construction. If you can "find" an OOK Receiver module in yours (i.e with just three pins and a "wire" antenna), then it may be possible to change it for a 434 MHz version. Various "Superhet" OOK types are available on ebay (particularly .com) for a few Pounds/Dollars, but check their rated supply voltage because many of those receivers (and transmitters) are intended for 5 volt operation, not the 3.5 volts that the FO's three AA cells may deliver. Larger than normally would be fitted in the FO Consoles, but the "RXB6" receiver module is generally considered to be quite competent.

Cheers, Alan.