Simulating Bad Signal conditions


#1

Hi,

I’m sorry if this question has been asked before, I’ve searched the forums and found no similar questions.

Does anyone know of a way to simulate Bad Signal/Network conditions such as network registration and bearer failures? We have an issue with our code out in the field with modems failing under bad signal conditions and not recovering. I believe the issue is fixed but want to simulate the same conditions to verify the fix, also need to test roaming networks with a world SIM.

I’ve tried to disconnect the antenna from the modem and terminating with a 50 ohm resister as suggested on another thread but the modem still has fair to good signal and doesn’t exhibit the error conditions.

Thanks

Mark


#2

What “other thread”? - post a link, so that we can see exactly what was suggested, and in context.

A 50-ohm resistor would no be a particularly good choice; what you need is a proper termination for your modem’s antenna connection - like this:


uk.farnell.com/radiall/r40410100 … dp/4196570

(that’s for an SMA connection; you haven’t said what “modem” - so I don’t know what connector type it has)

An inline attenuator will reduce signal strength:

uk.farnell.com/radiall/r41182012 … dp/4196727

Variable attenuators are also available.

And coaxial switches/relays - could be used to switch-in different attenuators.

These can be expensive new - but sometimes turn up on ebay…

Note that attenuators simply reduce the signal level - they don’t affect its quality.

For real-life testing, you need to set-up a mobile test rig, and take it into genuine poor signal areas; eg,

twitpic.com/3wgbh4


#3

Sorry the other thread is https://forum.sierrawireless.com/t/automated-tests/1953/4.

The modem we are using is an FXT009.

Thank you for the information, I’ll take a look.


#4

Then you do need SMA parts, as shown.