I wasn't trying to make an argument against it, and if someone did have an EMI problem which was hampering their efforts, and which could not be solved by using the inbuilt channel search functions, then they might out of curiosity decide to try to use another technique for finding the cause of interference which is over and above what a well trained engineer should do first of all, such as turn off all other known 2.4GHz sources and then reactivate them one at a time until the problem reoccurs.Originally Posted by lester
When I initially dealt with Telegesis for support they promoted the Wi-Spy as a form of surveying tool, preferably to be used prior to deployment of a wireless networking solution. In that respect it would be ideal if you can buy a cheap device and use it to discover that your chosen band is too noisy to begin, rather than pay out £100's on radios which can't break through the noise.
I see that Zigbee has now been fully certified for other frequency bands, and also that several manufacturers offer meshing radios on sub 2.4GHz bands which do the same as the 2.4GHz devices but in a band which has fewer devices assigned to it. This might be the better option when you are in a noisy environment on the 2.4GHz option.
Personally, I wouldn't pay for a Wi-Spy if I am in a typical domestic environment and look to introduce a small 2.4GHz network, when it is much cheaper to buy two £12 Zigbee modules and test them for yourself. It seems probable that if you discover a problem with Zigbee radios which you can relate to the environment being too noisy then at that point you should have already noticed poor wireless path reliability on your other 2.4GHz devices too, and that should lead you to choose another frequency band anyway.
I agree that it is sometimes useful to 'see' what is going on, but if you see a strong signal close by which does not cause interference, or if you see that the band is quiet, the radio units will still work noticeably well, but if there is a signal which causes interference you will definately know about it, unless it is so intermittent that to catch it you need data logging tools. Even then you might never track it down.
I used a Microchip 'Zena' Zigbee analyser which I would recommend buying as a useful tool for analysing data paths, packet data and wireless node settings. You can see at a glance where transmissions are being interfered with just by analysing the data being produced and if you're a newcomer to Zigbee and it's seemingly baffling modes of operation then the Zena will help you make sense of any problem which has to do with data transmission.
But, Zigbee is a bloated concept in terms of software, and my preferred devices (when they become as cheap as Zigbee that is) are going to be the 6LoWPAN radio devices, because they promise full IPV6 compatibility right down to node level, and in effect that means that any device can be given an IP address on the internet, very cheaply. These will also eventually be multiband devices so again there will be no need to stick to 2.4GHz
I don't know if such a lengthy comment was needed, and I hope it doesn't deter anyone from using Zigbee because if you find a vendor with a product as easy to interface with as the ETRX2 is then you can't really fail to be successful. Creating longer range data paths is as easy as adding another cheap Zigbee node in the datapath to act as a repeater and therefore radiated power levels never need to become so high as to cause interference to neighbouring devices. I think it is Stockholm in Sweden which has introduced smart power meters in every home, all working on a Zigbee mesh, and the reports are that interference issues have been kept to a minimum by careful channel selection on the Zigbee side, and no interference to other 2.4GHz devices has been detected due to the overall low power nature of the devices being used.
Chris
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