Product manual
100-M0131X1A 02/10/10 10 of 31
www.cobham.com/gms
After changing any “R/W” field with a new value the user must click on the APPLY button for
the change to take effect. Clicking on the CANCEL button (or Query button) will cancel the
operation (previous values are restored).
Field R/W Description
RF Freq (MHz)
R/W
RF input frequency at BDC (block down converter) input. The
receive frequency can be changed by entering the new desired
frequency in this field.
Bandwidth
R/W
This field displays the bandwidth of the received OFDM signal. It
should be set to the same bandwidth of the transmitter selected
from the following values: 6, 7 or 8 MHz or with optional
narrow bands 1.25 or 2.5 MHz
Guard Interval
R/W
User selects the guard interval which matches the transmitter.
Guard interval sizes are selected from the following values 1/32,
1/16, 1/8 or ¼. When in narrow band (1.25 or 2.5 MHz) guard
intervals are limited to either 1/16 or 1/8.
FEC
R
This field displays the COFDM FEC (forward error correction) that
is being demodulated at the receiver. FEC values are 1/2, 2/3, 3/4,
5/6. When in narrow band (1.25 or 2.5 MHz) FEC values are
limited to 1/3 or 2/3.
OFDM Mode
R
This field displays the COFDM constellation (QPSK, 16 QAM) that
is being demodulated at the receiver.
OFDM Polarity
R/W
This field displays whether OFDM signal is set to Normal or
Inverted Spectrum.
Table 1 – RF Field Definitions
2.6.2 Link Status Group
This group consists of read only fields (status indicators) along with a “Polling Enabled”
checkbox and an “Update Status” button. The indicators are for both receiver A and receiver
B (diversity inputs). The fields are shown in Table 2 below with a description.
Field R/W Description
Level
R
This field indicates the received signal level. Normal levels are
around -15 to -90 dBm. Keep in mind signals greater than -15
dBm will overload the front end (BDC-s) and cause poor
performance and signals less than -90 dBm may be too weak.
The gain settings of the BDC-s will affect these readings
SNR
R
Input Signal-to-Noise Ratio. This read-only field conveys the
SNR of the received signal as measured by the demodulator.
Value expressed in dB. In QPSK: values greater than 13dB
represent strong RF signals. In 16-QAM; values greater than
18dB represent strong RF signals