Comtech EF Data SFC1800A - Manual (Page 38)

User Interfaces SFC1800A Synthesized Frequency Upconverter
4-14 TM111 - Rev. 1.0
4.2.7 Test Menu Options and Parameters
REF OFFSET:
{0000 - 4095}
The REF OFFSET field of the Test Menu allows the
operator to adjust the frequency of the 10 MHz High
Stability Internal Reference and vary the output of the
Synthesized RF LO by
± 999 parts per billion (ppb). One
part per billion represents a change of 1 Hz per GHz (1
billion Hz) of output frequency. Thus, each unit of ppb
will allow a change in accuracy of the converter of
1 x 10
-9
.
The exact frequency of the LO Output can be calculated
from the displayed frequency on the converter front
panel as follows:
C-Band Upconverter
(70 MHz IF)
LO = Tx Freq. - 1182.5 MHz
C-Band Upconverter
(140 MHz IF)
LO = Tx Freq. - 1252.5 MHz
C-Band Upconverter
Extended (70 MHz IF)
LO = Tx Freq. - 1182.5 MHz
C-Band Upconverter
Extended (140 MHz IF)
LO = Tx Freq. - 1365.0 MHz
Ku-Band Upconverter
(70 MHz IF)
LO = Tx Freq. – 1770.0 MHz
Ku-Band Upconverter
(140 MHz IF)
LO = Tx Freq. – 1840.0 MHz
The RF Monitor output can be measured with a
frequency counter of known calibration.
The stability of the 10 MHz Reference is related to the
temperature of a 10 MHz crystal inside the unit. A
proportionally controlled oven around the crystal
maintains the temperature in the oven to 0.1°C. In
addition, the precise temperature that the oven
maintains has been determined empirically for each
crystal during manufacturing. As long as the ambient
temperature stays within limits (0 - 50
°C) the reference
will maintain stability of greater than 1 x 10
-8
(refer to
Figure 4-2).