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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?

On Thu, Jun 29, 2017 at 02:29 pm, Michael Babineau wrote:

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.?

Hi Michael,
Yes, you're right, it's not a 100% perfect method, the diminished sidetone on initial key-down is a result of that cap charging up - I have exactly the same behaviour here.

I am contemplating injecting the sidetone at the volume control (before the LM386) to see if this works any better

If you find a minimal mod that gives a better sidetone please share it and I will update the modification instructions - thanks!

73 Allard PE1NWL

I think Allard's solution is likely minimal and acceptable. ?For not so minimal, here's somebody who has added sidetone injection at the volume control:
??/g/BITX20/message/27410
and also solved the rx kerchunk.
A few notes here on exactly what the devil that diagram might be trying to say: ?/g/BITX20/message/28942
If all you want is sidetone injection, should be possible with 1 or 2 resistors out by the volume control.

Jerry

On Thu, Jun 29, 2017 at 02:29 pm, Michael Babineau wrote:

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 :

Mine behaves the same way. I haven't found it annoying enough to bother trying to do anything about it though.
?
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John - WA2FZW