2960AR/2965AR/2975AR Manual
ues showing the saved state of internal registers. These
are for factory use.
3.9 Signal Outputs. The 2960AR has three front
panel outputs of 10MHz(2) and 5MHz. Each has a
nominal amplitude of 1Vrms into 50Ω. The 2965AR
and 2975AR have three front panel outputs of
10MHz, 5MHz and a 100Hz to 50MHz synthesized
output. Each has an amplitude of 1Vrms into 50Ω.
3.10 See section 5.0 for the rear panel 1pps IN and
OUT characteristics and use.
4.1 Power on. After power is applied, the 2960AR
and 2965AR POWER OK LED will be green.
This indicates that the applied line power is within
tolerance and the unit is functioning. The 2975AR
will display the software version for 5 seconds and
then switch to indicating warm up mode.
4.2 Rubidium Warm-up. After power is applied,
it will take up to 20 minutes to reach Rubidium
Lock. After the warm up period the Rubidium
Lock LED will change from red to green
on the 2960AR and 2965AR and the 2975AR will
display the synthesized frequency setting.
NOTE:
During the Rubidium locking process, the front
panel RUBIDIUM LOCK LED may switch between
red and green. A steady green indicates LOCK.
4.3 Proper operation, without a 1pps connection, is
indicated by agreen POWER OK LED and a
green RUBIDIUM LOCK LED with the 1pps
LED off (2960AR and 2965AR) or, dashes on the
second line of the 2975AR display.
NOTE:
The specified accuracy will be met within a few
hours after power-up. For applications requiring
verification of long-term stability, the periods shown
in the specifications will have to be met.
4.4 See the section “1pps Operation,” below,for
details on 1pps connections and operation.
4.5 Serial control of Synthesizer The user host
computer software must properly format the serial
commands. Incorrect formatting will result in an
error code being returned. See Table 1 on page 3
for a list of RS232 error codes.
4.6 For maximum interface speed, it is suggested
that Echoing be disabled by the “E D” command.
This will allow the host to send characters at a
faster rate. Flow control must be provided by
the host. The 2965AR and 2975AR will respond
with an “OK” for acorrectly received data
command. If your host software parses this “OK”,
you will be assured that the command has been
correctly received and you may send your next
command. You will have to verify correct operation
at your host rate.
5.1 1pps In and Out. There are rear panel
BNC receptacles which accept a 1pps input and
provide a 1pps output. Use of 1pps allows
synchronization of multiple units, as well as
providing a means of auto-calibration.
5.2 A long-term stable 1pps signal is typically
derived from a GPS (global positioning system)
receiver or from another frequency standard. Both
units will autoadapt to the supplied 1pps and
adjust the internal Rubidium Oscillator to match
the long term average frequency derived from the
1pps. The auto-adaptive algorithm selects the best
tuning time constant based upon the stability of your
supplied 1pps.
5.3 For low-jitter 1pps inputs (<20ns), the approxi-
mate tuning time constant will be 1,000 seconds. A
typical timing receiver system, such as the GPS1
(with approximately 100ns peak-peak 1pps jitter),
requires a time constant of approximately 10,000
seconds (about 3 hours) for optimum tracking.
5.4 For noisier 1pps inputs, such as those from
standard GPS receivers not intended for timing
applications, the time constant may increase to
100,000 seconds. If the input is too noisy, as
determined by the auto-adaptive algorithm, the 1
PPS LOCK light will not illuminate.
NOVATECH INSTRUMENTS
