This week a colleague of mine was invited to undertake some tests to see how our devices worked when installed under manhole covers. We were told to expect poor results as others had struggled in the past but the device performed really well. We were presented with 3 types of manholes (light, medium & heavy) and we did some testing with both GSM (GPRS) and 169MHz radio equipment.
Things went really well with us being able to communicate from beneath all three types on manholes with both GSM (GPRS) devices and the 169MHz radio kit.
So why is it we have succeeded where others have failed..? First of all with the GSM (GPRS) equipment we have a well tuned antenna but more importantly we do some clever power management making sure the GSM device gets plenty when it needs it making communications as robust as is possible.
Frequency also has an impact. The higher the frequency the waves the harder they find it to burrow through objects such as manhole covers. Different GSM operators use different bands. We use multi network sim cards to give us the best performance possible. The frequency is also why the 169MHz radio equipment has worked so well.