Service manual

Model 2A Operation And Service Manual
2A Manual A5 21 January 2005 Page 7
Model 2A Off Air Frequency Standard
Getting Started- Some Useful Notes
1. Connect a mains lead to the IEC socket on the rear panel- first ensuring that
the mains “
SUPPLY" switch is in the "OFF" position. This indicates that the
unit is receiving no mains power. Also ensure that the "
ON-OFF" knob on the
front panel is also in the "OFF" position.
2. Open out the loop aerial to encompass as large an area as possible and connect
the
BNC connector, at the end of the thin coaxial cable, to the BNC
“
AERIAL” input on the rear panel. It is important that this connection should
be made before applying mains power to the unit, in order to guard against
accidental aerial supply short circuits when the plug is inserted.
3. Turn on the mains “
SUPPLY”, using the switch, just above the IEC mains
input socket. If fitted, switch the front panel "
ON-OFF" knob to "ON" and
the “
METER” knob to "dc". The meter needle rising to approximately the gap
in the scale will confirm the presence of the internal 12V supply.
4. Turn the “
METER” knob to the "Rx" position. Careful rotation of the loop
will enable maximum signal to be obtained - reading somewhere between the
gap in the scale and full-scale deflection. Alternatively, the loop may be very
carefully rotated about its vertical axis until a sharp dip in the meter reading is
seen. The optimum loop orientation is then at right angles to this.
5. Turn the “
METER” knob to the "PLL" position. The meter's needle should lie
approximately at the gap in the scale. Ambient temperature variations between
the factory and your particular operating area will cause slightly different
indications.
6. The "Loss of Lock" red
LED, which is an out of lock warning, should stop
after about 30 seconds, indicating that the instrument has achieved lock. The
“push” button switch should be pressed once to re-set the warning system.
7. Outputs, which are inhibited when the system is out of lock, are now available
from the
50Ω, BNC front panel sockets.
Important Note: Problems may occur with localised RF interference from
PCs, Invertors, etc…. Also surrounding metalwork and the metal in a building's
structure may also influence the received signal levels, their phase and the apparent
direction of the incoming signal.