[Elecraft] KX-3 Transmit Audio - Echo on TX SSB - interesting find

[Walter Underwood]

You can tame the bass with TX EQ and RX EQ. 

You don’t want to use the logic bias from the up/down buttons, because that is noisier than the mic bias. It is possible that you had odd audio because you had both bias supplies. That usually results in lower mic output.

This message has an investigation into mixing mic and logic bias:

https://groups.yahoo.com/neo/groups/KX3/conversations/topics/9556 <https://groups.yahoo.com/neo/groups/KX3/conversations/topics/9556>

And this blog post has a simple solution:

http://observer.wunderwood.org/2015/08/16/yamaha-cm500-headset-with-ptt-on-elecraft-kx3/ <http://observer.wunderwood.org/2015/08/16/yamaha-cm500-headset-with-ptt-on-elecraft-kx3/>

wunder
K6WRU
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Oct 18, 2015, at 8:12 PM, paulb <xtr348165 at xtra.co.nz> wrote:
> 
> 
> Hi Folks
> 
> I have owned a KX-3 for a couple of years, have fitted the filter
> board and auto-tuner and a set of internal batteries and charger.
> Certainly a tidy package.
> 
> Something I like using is a small light headset aka cheap and cheerful
> pc gaming type hardware.  i use these on my K2 and K3 with great results.
> The heavy bass needs taming down, simple RC filter does the trick.
> 
> From day one the KX-3 seemed very bass heavy.
> Something didn't sound
> quite right, an odd echo on SSB with higher mic gain settings.
> Bias for the Mic was enabled to power the insert. 
> Setting for TX EQ  -16 for 100 200 400 hz.
> 
> I added a 0.047uF cap into the mic line to roll the low end audio.
> This prevents the mic power from working, so figured the
> unused mic up/down line could be used. It is about 2.5volts
> in series with 5.6k. So we now have a working mic,
> with minor internal changes at the mic socket.
> 
> But the echo seemed if anything worse at higher mic gain.
> 
> Now as a  long shot terminated the mic up/down line with about 10uF electro.
> This would ensure the bias supply is clean.
> 
> Echo is now gone. Totally.
> 
> I suspect what is happening is headset plugs are sitting accross the
> up/down line, some audio is ending up where is should not be.
> 
> I am well pleased. The 3 components ( 0.047uF  5.6k  10uF ) can be 
> mounted directly on the KX-3 mic socket. It's a squeeze but works well
> 
> cheers from ZL
> 
> Paul 
> zl1ajy
> 
> 
> 
> 
> 
> 
> 
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KX-3-Transmit-Audio-Echo-on-TX-SSB-interesting-find-tp7609274.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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