Adjacent Channel - Berkeley Varitronics Systems Fox Manual

cies. If the center is greater than either of the adjacent frequencies, this value is plus (+). If either of the
adjacent are greater than the center, this value is negative (-). The difference between the center frequency
and the adjacent frequency is determined by the last setting of the FREQ STEP in the VAR SWEEP measure-
ment screen. Starting from current frequency, push
greater than 100 dBm in RSSI and
100 dBm in RSSI.
Fast Fade saves blocks of 64 consecutive samples
of dBm in PCMCIA card records. Also included in
each block is the time, date and GPS position of
the measurement.
Measurement Rates
FOX RSSI measurements are performed by a high-
speed 8-bit A/D converter. The actual sample is made rapidly, in about 200 microseconds. This is not, however, the amount
of time to record a single signal strength. Due to variations in the instantaneous amplitude of RF signals, some averaging
must be applied to the readings to "normalize" the
measurements. Therefore, multiple A/D samples
are added together and divided by the number
of samples to provide an integrated value and
a 'smoother' measurement.
are under user control, as shown in the tables on
the next page. They prevent measurement errors
which may be caused by noise or fast changes
in amplitude due to local reflections and attenu-
ations. A brief explanation follows so you can
choose the optimum rate of integration.
Each one of the 64 signal strength samples is the average of 1,2,4,8 or 16 A to D measurements (selected by the
user.)
The dBm value that is displayed on the
(also displayed is PCMCIA storage and GPS status.)
Each AD sample of RSSI takes the
The time between samples is fixed (150usec), only the # of samples is currenly adjustable (1 CHAN measurement).
NOTE: The FOX display update and PCMCIA read/write overhead is about 60 msec, so that when using sample rates of 1,2 or 4,
the number of measurements per second is limited by this overhead time.
SHIFT
FAST FADE (optional)
These parameters
FOX
screen is the average of the 64 samples (A/D samples) saved on the PCMCIA card
FOX receiver 150usec, so that an average of 64 samples takes about 10msec to accumulate.

ADJACENT CHANNEL

The adjacent channel measurement is used to
measure any frequency and the two frequencies
immediately adjacent to it. To select the center
frequency, press
quency. This measurement displays the dBm read-
ings of all three frequencies in both bar graph and
digital formats. It also displays the comparison of
the center frequency against both adjacent frequen-
SHIFT + UP ARROW
+ DOWN ARROW keys to seek next lowest frequency greater than
Page 7
ENTER and enter the center fre-
key to seek next highest frequency