Zonge GDP-32 - Powerline Noise Rejection

GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 12, Page 12
12.4 POWERLINE NOISE REJECTION
Field tests have demonstrated that in general the new binary crystals (4.980736 MHz) provide
superior powerline noise rejection over the original 5 MHz crystals. The new crystals provide an
exact binary frequency range so that stacking and averaging can be synchronous with the
powerline frequencies.
Following are the test results for the old (5 MHz) crystals for various repetition rates
(frequencies):
50 Hz 60 Hz
Freq Rejection Freq Rejection
32 Hz 2000:1 32 Hz 2000:1
16 140:1 16 700:1
8 250:1 8 20:1
4 250:1 4 50:1
2 80:1 2 700:1
1 250:1 1 333:1
For the new (4.980736 MHz) crystals:
50 Hz 60 Hz
Freq Rejection Freq Rejection
32,16, 10,000:1 32,16, 10,000:1
8,4,1 Hz 8,2,1 Hz
2 Hz NONE 4 Hz NONE
With the new crystals (4.980736 MHz), the powerline rejection is nominally greater than
10,000:1 for all frequencies EXCEPT 2 Hz for 50 Hz noise and 4 Hz for 60 Hz noise.
Note: The 2 Hz repetition rate should not be used around 50 Hz power systems, and 4 Hz should
not be used when you have 60 Hz power systems. There is no effective rejection for these two
repetition rates.