Using your iPhone in ‘field test mode’ to check for cellular coverage
With Cisco Meraki announcing their new MG line of products I thought I’d write up how I’ve previously checked for the best place to mount cellular modems. Whenever I’ve previously done this I’ve had to hash together a ‘hack’ to get Meraki to use a cellular link as WAN2 rather than just a failover; or in some instances WAN1 where 4G is better than the ADSL connection available from Openreach (the company that run most of the cable in the UK). This was previously accomplished by taking a Z1/Z3 with a USB 4G dongle attached and mounting it in an outdoor enclosure and then running Ethernet back to the main MX device. This was a more expensive way of doing what we’ll now be able to do with an MG. Not to mention the fact that you were paying for an ‘all in one’ device to literally convert a USB dongle into an Ethernet connection… I’ve been asking Meraki for this for a while! That’s at least one thing off the list. I have LOTS more!
Anyway… we normally use the same 4G provider in the UK as I have on my phone (Three). The main reason for this is that until recently they were the only operator in the UK to offer an ‘unlimited’ and ‘non-throttled’ data package. We’d get a pay monthly sim for £24 a month and if we used that in one 4G dongle in particular (trade secret - DM me and I’ll tell you) Three wouldn’t be able to discern that the SIM card was being used in a dongle and not a normal smartphone. All that to say that it meant I could use my phone to test the best place to mount the Z1/Z3. All I had to do was use my phone to find the place with the strongest signal. So how do you do that on an iPhone?
There’s something called ’Field Test Mode’ on an iPhone and you get to it by dialling:
*3001#12345#*
Quick Tip: Add this to your phone as a contact but to use it you’ll have to copy and paste the number into the keypad.
Hit the ‘call’ button and you’ll be taken to the hidden field test mode app.
To find the nearest cell tower signal go into LTE > Serving Cell Meas - and look for ‘rsrp0’ - this is your closest cell tower. If you want to find somewhere with a good balance of two cell towers find ‘rsrp1’ and that’s the signal strength of your second-best cell tower.
It’s important to remember that this won’t be the signal received by the MG/Z1/Z3 (Different antennas etc) but it’s a good indication you find the best place to mount your cellular receiver.
Just as a side note… I’m excited to see that the MG will come with the ability to add a directional antenna or at least an external antenna. Just need to know pricing and availability now!
