PLJ-8LED Frequency Counter User Operating Manual 12
APPENDIX : TESTING AND MODIFICATIONS
1. ACCURACY
The accuracy of the measured frequency was tested by F6CQK using an EPOC quartz oscillator
calibrated from a rubidium clock. This showed an error of -10 Hz. This was easily corrected using the
calibration adjustment available near the TCXO.
A measurement over 24 hours shows a stability better than 1 Hz.
2. SENSITIVITY
The sensitivity of the module was measured by F6KEH, shown below:
Low Channel (CH L)
High Channel (CH H)
3. SCHEMATIC AND MODIFICATIONS
It is noted that the UHF channel allows measurements up to about 450 MHz. This path comprises a
divide by 64 stage claimed to be able to operate to 2.4GHz according to the published specifications.
It is therefore surprising that the sensitivity fell as quickly as it did. The problem could come from the
automatic channel switching. Unfortunately no schematic is provided in the Chinese instructions.
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