1. Most SCADA networks get a lot done with very limited bandwidth (28kbps is typical) by being thrifty with thier transmissions - only sending when there is a state change and strictly limiting polling.
2. A simple PING can starve a SCADA link. If you do use a PING to test a low Bandwidth link be sure and be patient. If you don't see responses with a standard PING, try using the "ping -w xxxx" command. The defualt for a ping is 4000, or 4 seconds. Try extending it and waiting longer.
3. Your Windows laptop with lots of defualt protocls turned on can starve a SCADA link. Windows by defualt wants to advertise and poll for lot so things that make it easy to share files, folders, printers, etc. All those that don't add up to much at all on your 100Mbps + home network can overwhelm a 28kpbs network. In this case using a very stripped down version of LINUX, like Puppy Linux that can be booted from a USB flash drive to do your configurations and testing can take a lot of the mystery out of the process.
4. If you are still not sure, use the tools built into the radios to test the circuit.
5. Remember that SCADA links by defualt have the best performance upstream, from the edge toward the core. This is by design but it is opposite the defualt performance of most broadband multipoint solutions like the PMP450 or the ePMP. Keep this in mind when evaluating performance.
It can be tough to get used to a low bandwidth world, but remember even the internet started for many with a 28kbps dial up connection. You can get a lot done with a low bandwith circuit, if you are smart about it.