I was curious about a couple of things that I noticed while looking at link
test signal values from an AP-1000 Base Station that is using EnGenius 200mW
cards.
1> The noise value always seemed to be -101dBm so this made me wonder if the
reading was valid.
Results: Using a CW to interfere individually with both the Base Station and
the Client, I found that the noise reading is actually very close to what the
spectrum analyzer saw.
2> I've wondered why the modulation was locked at 2Mbit/s on our systems.
Results: Local noise level of more than about -93dBm seems to cause the
AP-1000 to start operation at 2Mbit/s. If the local noise level is lower than
about -97dBm, the system will start operation at 11Mbit/s.
What I did: Using a power inverter in my car, I started the AP-1000 in various
noise environments. The local noise levels were examined with an IFR spectrum
analyzer (also in my car). As I drove away from and towards base stations
(the source of my noise for testing purposes) I found that somewhere between
-97dBm and -93dBm the AP-1000 would start operation at 2Mbit/s or 11Mbit/s.
Note: Whether starting in a noisy area and moving to an area with no noise or
vice versa, once the AP-1000 is locked at a certain bit rate, it stays locked
at that rate. I even went so far as to introduce the 30dBm CW to the Base
Station to see if I could knock it down to 2Mbit/s or less - the client still
reported 11Mbit/s while the Base Station connection came and went from the
interfering signal.
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