Model A3-B Operation And Service Manual
A3-B Manual 30 November 2005
Page 5 of 5
Model A3-B Quartz Oscillator
Introduction
The Model 3 quartz frequency standard is based upon a new design of oven controlled crystal
oscillator and will give excellent service over long time periods. The unit is fed from an external,
switched mode power supply working at 50/60 Hz and supplied from a mains source of between
110 V and 240 V (r.m.s.).
Facilities Available
This equipment is fitted with the following outputs, as standard, all of which have the same
high accuracy as the 10 MHz oscillator itself:
Front Panel
The front panel is fitted with 8 B.N.C sockets on its left hand side, supplying 1, 5 &10MHz sine
wave at a level of +13 dBm into 50
Ω
; 1, 5, 10MHz square wave at >2V ttl; 1pps sync input; 1
standard optional output.
Back Panel
On the extreme left hand side of the back panel, the XLR power plug should be mated with the
XLR line socket from the external, switched mode power supply. The mains supply should then be
connected to the three pin plug on this switched mode supply. The XLR plug next to it has been
included for the battery backup supply, available as an extra option. If this option is not selected,
then this plug is left unconnected.
Very Long Term Frequency Adjustments
On leaving the factory the unit will have been adjusted against a hydrogen maser frequency
standard, to within 1E-11.
However, it is appreciated that quartz crystal oscillators will tend to drift (upwards) in frequency
over long time periods, due to crystal ageing. Should the customer consider that the drift eventually
renders the unit in need of correction, the following should be carried out:
EITHER
Return the unit to Quartzlock for readjustment against the hydrogen maser there
OR
If a high accuracy frequency standard is locally available, remove the six lid retaining
screws and locate the blue, 10 kR, 20 turn potentiometer, next to the OCXO unit. Very
carefully adjust this potentiometer until the frequency is within acceptable limits. A
comparison frequency standard, whose accuracy is better than 1E-12, is recommended for
this adjustment.
