Dear Elecrafties,
Thank you for your very helpful feedback suggestions, particularly those who
directed me to look for gremlins in the bandpass section of the subRX as the
most likely cause of intermittent subRX operation on 40m. As suggested I
took a close look at the soldering on the enamelled wire leads from the 40m
toroids and sure enough found the solder does not appear to have flowed
properly along the leads on the component side of the board, perhaps due to
incomplete cleaning of the enamel from the wire? That does look
suspiciously like a gremlin hideaway. Unfortunately, it's not feasible to
clean or resolder the toroids from the component side without first removing
some of them as they are quite tightly packed. The reverse side of the
board showed no obvious signs of dry joints but I spruced up the 40m toroid
solder pads there just to be sure. So far so good: the radio is all back
together and 40m works fine on both the main and subRX. Fingers crossed.
The 20m toroids appear to have the same limited solder flow on the component
side so I'll keep a close watch for gremlins there too ...
For those of you currently building the subRX, I'd suggest a careful look at
the soldering of the bandpass toroids for possible gremlin droppings before
putting the subRX board into its aluminium box.
73 all and thanks again for the rapid diagnosis. You guys rock.
Gary ZL2iFB
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