Signal strength tests. "Local" devices are on lab bench, about 5 cm apart.
"Distant" device is in the adjacent room, separated by one thin brick wall
and 4 m of air.

TX is requested 0 dBm (effectively -0.2 dBm). Transmission is without
CSMA-CA and ARQ. Results are LQI and ED (dBm). "garbled" is a bad CRC and
corrupted frame content. "-" is no reception.

Distant		Local
---------------	---------------	---------------
100813-red	100813-orange	100908-B

TX		255, -90	255, -90
TX		255, -90	garbled
TX		255, -90	255, -90
TX		255, -90	255, -90
TX		255, -90	255, -90

-		TX		garbled
garbled		TX		255, -52
255, -89	TX		255, -52
255, -89	TX		255, -53
-		TX		255, -53

255, -88	255, -48	TX
255, -86	255, -46	TX
255, -86	255, -49	TX
255, -86	255, -49	TX
255, -87	255, -49	TX

100813-red	100813-orange	100908-A

TX		255, -90	garbled
TX		255, -89	180, -89
TX		255, -87	196, -89
TX		255, -87	148, -89
TX		255, -87	-

255, -86	TX		garbled
255, -87	TX		255, -49
255, -86	TX		255, -49
255, -87	TX		255, -49
255, -86	TX		255, -49

-		garbled (-44)	TX
-		-		TX
-		-		TX
-		-		TX
-		-		TX

100813-red	100813-orange	100908-A (reworked)

TX		255, -87	255, -87
TX		255, -87	255, -88
TX		255, -87	255, -87
TX		255, -87	255, -88
TX		255, -87	255, -88

255, -86	TX		255, -56
255, -86	TX		255, -57
255, -86	TX		255, -58
255, -86	TX		255, -58
255, -86	TX		255, -58

255, -85	255, -52	TX
255, -85	255, -52	TX
255, -85	255, -52	TX
255, -86	255, -52	TX
255, -86	255, -52	TX


Conclusions
-----------

- 20100813 (atusb) and 20100908 (atusd) board show similar performance when
  at least one station is an atusb

- resistive divider doesn't work

- no clear indication of whether capacitative divider causes interferences.
  Marked difference in one series of tests but the others look the same.

- reception level is about 4 dB above workable minimum. (Specified receiver
  sensitivity is -101 dBm, but things start to deteriorate around -90 dBm.)
  We have a reserve of 3.2 dB for transmission (used -0.2 dBm, maximum is
  +3.0 dBm).
