Topic: 433MHz or 868MHz (UK)

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Most weather stations marketed in UK use the 868MHz band as that is reserved for sensor transmissions.

But 433MHz is also legal in UK for such uses.

The preferential marketing of 868MHz kit in UK/Europe seems to be due to an assumption of a higher risk of interference from a busy radio environment on 433MHz because 433MHz can be used for several purposes other than sensors.

However (at least in theory) 433MHz has advantages as it may transmit further and pass through walls more effectively. Also I've been monitoring the radio activity in my area using RTL-SDR and SDRSharp and find very little activity on 433Mhz and lots on 868MHz.

Some of the local 868MHz activity is quite strong and has frequent signals because it originates from my own property! e.g. pulses every second related to my MyEnergi hub, harvi, zappi, every 15 seconds from my central heating controller, and so on. On 433MHz I have just one device transmitting once an hour (heating oil tank monitor). Activity from my neighbours is weaker because I live rurally and my nearest neighbour is 450m away, but there also I am seeing little 433MHz activity and a lot of 868MHz activity.

I'm intending to buy an Ecowitt WS90 from shop.ecowitt.com. I'm particularly interested in getting a good range because my intended location is about 120m from the GW1100 receiver. Is there any reason why I shouldn't select the 433MHz option instead of 868MHz (other than that I will have to buy a 433MHz GW1100 as well)?

[Vasco]

I'm particularly interested in getting a good range because my intended location is about 120m from the GW1100 receiver.

Can you check the 433/868 MHz specs for typical transmission range? For example my WMR200 (admittedly very old technology!) is 433 MHz and the specs say "up to 100 metres with no obstructions": I consider myself lucky if I get 30 feet through a brick cavity wall. . . I have no idea what a typical sensor transmitter power is, though.

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With a bit more research I think I've resolved my question.

I noted the theoretical range and object penetration benefit of 434Mhz over 868MHz, other things being equal. However other things are not equal.

In the UK the entitlement to use 433MHz or 868MHz without licenses requires adhering to certain use parameters, such as power output and duty cycle (duty cycle is the % of time spent transmitting). Here are the rules on that applicable to UK

https://www.ofcom.org.uk/__data/assets/pdf_file/0028/84970/ir-2030.pdf

A complex document. But as I read it the maximum power allowed in UK in 433MHz band is 10mW if operating on a 1% duty cycle (e.g. transmitting for half a second every 50 seconds). For higher duty cycles the maximum power is reduced to 1mW.

For the 868MHz band up to 25mW is permissible for low duty-cycle operations (such as frequent but short packets of weather data).

There is more detail in the document, and more rules than I've mentioned (e.g. different rules apply to different parts of the 868MHz spectrum) but that is the main take-home message for me.

If Ecowitt have made their 868MHz devices transmit on maximum power to obtain maximum range then the extra power transmitted will likely provide better range than the lower powered 433MHz devices.

Of course Ecowitt may have opted not to transmit at the maximum allowable power so as to conserve battery, so comparative testing of devices using the two frequencies would be required to be sure.

Another consideration is that if Ecowitt market their 868MHz devices as suitable for UK/EU market, and the 433MHz devices as suitable for Oceania, they will have built their 433MHz devices to be compatible with Oceania rules which might not be compatible with UK rules (e.g. they may have higher power output or higher duty cycles which would make them illegal in UK).

And one more consideration is that though I'm not detecting many devices locally in 433MHz band when I scan with RTL-SDR and RTL_433, there might be 433MHz noise that I am not detecting such as intermittent amateur radio - 433MHz band may not be as clear and available as I think.

I'm not equipped for comparative testing of 433MHz vs 868MHz, but I can test the range of the 868MHz devices that I have. If I place my GW1100 gateway on a window ledge at the side of my house facing my intended anenometer location 120m away, a WH32 held in the air at that 120m distance does transmit successfully to the GW1100 

It also occurs to me that the GW1100 does not have to be indoors. I have outdoor wifi booster (TP-Link EAP110) so I could place the GW1100 and a USB powerbank in a waterproof container partway between house and anenometer, and visit it occasionally to swap over to a full powerbank. It would be nearer to the anenometer and so well-placed to make an RF connection, and within range of my wifi signal to connect to the Internet. Add a solar panel and I wouldn't even need to visit it to swap powerbanks.

So regardless of whether a 433MHz device might be better for me (which now seems unlikely) it seems an 868MHz device will work so I may as well follow the herd and get an 868MHz device!

[Vasco]

If I place my GW1100 gateway on a window ledge at the side of my house facing my intended anenometer location 120m away, a WH32 held in the air at that 120m distance does transmit successfully to the GW1100 

That's the sort of testing I like 

Did you try it in the rain as well? I frequently lose a sensor or two for a while when it rains (but that's because of wet walls/flat roofs, I think).

[zoomx]

And one more consideration is that though I'm not detecting many devices locally in 433MHz band when I scan with RTL-SDR and RTL_433, there might be 433MHz noise that I am not detecting such as intermittent amateur radio - 433MHz band may not be as clear and available as I think.

If you want detect (but not decode) all transmission and noise you should use SDR-SHARP or an equivalent. I don't know if recent version can also decodes.

[src]

And one more consideration is that though I'm not detecting many devices locally in 433MHz band when I scan with RTL-SDR and RTL_433, there might be 433MHz noise that I am not detecting such as intermittent amateur radio - 433MHz band may not be as clear and available as I think.

If you want detect (but not decode) all transmission and noise you should use SDR-SHARP or an equivalent. I don't know if recent version can also decodes.

Yes thanks. I used SDRSharp with the rtl_433 plugin. I detected/decoded some devices though not many in 433MHz band, far more in 868MHz.