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 Missing Track on V1.0 PCB

1. Background

A short section of missing track has been identified on the version 1.0  PCB. This affects the performance of the NE567 in noise. The missing section is in the "anti-chatter" circuit formed by R11/C15, this circuit suppresses multiple output pulses from the PLL during noise or when detecting a weak signal near the PLL capture threshold. Whilst the post detection filtering employed in the Microcode firmware provides good detection performance for weak signals, connecting the anti-chatter circuit offers a useful improvement in detection performance.

R11/C15 form a series high pass network between the output of IC2 the PLL pin 8 the input of the output stage of PLL on pin 1. The section of missing track is between C15 and IC2 pin8. These two pads are adjacent to each other and are easily connected by soldering a short wire link between the pads. When soldering in the wire link, be careful to avoid inadvertently bridging the small gap to the R18 pad which is in close proximity to the free pad of C15.

The diagram opposite represents the underside view of the PCB in the area of IC2 and C15. The red track illustrates the position of the link.

3. Acknowledgement

Our thanks to Graham Yoxall for identifying this omission.