I finally got all of the CW mods made to my BitX40 and it seems to be working fine using Allard's V1.16 code. ?However, I have noticed some strange behaviour?from the CW sidetone implemented using the recommended hardware mod :
What I have noticed is that when I key the rig I hear the sidetone, but after a second or two the volume of sidetone increases quite a bit (maybe double).
This doesn't seem to be the case when I use SPOT (i.e. the level stays consistent with SPOT).
I am just wondering if others experience the same thing or whether this is just my rig ? I do have a small RC filter in place of the 1K resistor, that consists of?
two 1.5K resistors in series, with a couple of ?0.1 uF caps to ground, the idea is to clean-up the square wave sidetone so that it sounds a little cleaner.
These are pretty low value caps so I can't see that they would have any impact on the sidetone volume.
I did notice that working backwards in the schematic ?from the speaker, there a good sized electrolytic cap (C111 470 uF) and I am wondering if the
diminished sidetone on initial key-down is a result of that cap charging up. If that is the case then others who are using this mod should be experiencing the same behaviour.?
I am contemplating injecting the sidetone at the volume control (before the LM386) to see if this works any better, but for now I was hoping to figure out
whether others are seeing the same thing.?
Cheers
Michael VE3WMB?
