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K2 s/n 5361 SSB TX audio problem

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ON4WIX

K2 s/n 5361 SSB TX audio problem

Hi all

I'm experiencing a funny problem with my K2 s/n 5361.
My KSB2 board went through intitial testing without problems, all measured values were OK as per the manual.
My TX audio however is horrible. It sounds very choppy (one ham reported to me it sounds 'very restrained'), it seems like the signal is cutting out and then switching back on in a very rapid fashion. I get almost no ALC reading when modulating, neither speaking very closely into the microphone nor a few inches away.
At first I thought I was experiencing the well-documented low mike gain problem. When speaking very closely to the microphone (a Kenwood MC43) the audio sounds reasonably clear (distorted but not much gets chopped out) but as soon as I move away from the microphone the chopping effect kicks in. This led me to believe that my mike output level was too low and that the KSB2's noise gate was operating on its gating threshold.
I then connected a preamp between the mike and the K2. With the K2 connected to a dummy load I listened to my TX signal through my Kenwood TS570. Varying the preamp gain made no noticeable difference, the audio kept sounding distorted.
I then tried the R14 mod (changing the 1k R14 into a 10k resistor). No solution, still very crappy audio (I disconnected my preamp at this stage).
At that moment I discovered a funny thing: when speaking into the mike at a distance of approximately 1 foot I noticed that my audio was almost sounding natural. Of course I was not getting any power out of the K2 this way. When I moved the mike closer to my mouth the distortion quickly came back.
So, at this moment it looks like I'm grossly overmodulating when I speak at a normal distance from my mike. It sounds a lot better when I speak far away from the mike but then I'm really running QRPp, hi.
I've taken the KSB2 board out of the K2 and checked all soldering joints (which seem OK). One of T2's leads looked suspicious so I desoldered T2 and rewound it with the little spare wire I had left and resoldered it. Still no luck.
Receive audio is OK so the filters seem do be doing fine.

Any suggestions on where to start looking for the cause of this problem are more than welcome.

Thanks in advance

Glenn ON4WIX
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ON4WIX

Re: K2 s/n 5361 SSB TX audio problem

Hi John (and all at the reflector)

Thanks for your answer.
I just grounded the mic jack housing following the guidelines I found on the
Elecraft web site.
No improvement however. I have tried different compressor settings (and
bypassing it) but this does not improve or worsen the audio.
When I hold the microphone about 1 foot from my mouth the audio seems OK but
of course I'm not putting much power out. Moving the mike closer to my mouth
the choppiness quickly becomes apparent. When I press my lips against the
mike it sounds slightly better although rather distorted, a bit like the
famous recording of the first man on the moon "A small step for man but a
giant leap for mankind".
I carried out my test on 40m. The thing that struck me also was that I got
very little ALC reading, only 1 bar lighting up occasionally. That one LED
didn't flicker along the rhythm of my modulation either. It just flickered
on and off in a quick fashion and stayed lit for about half a second after I
stopped talking.
I recorded my test a few minutes ago. If anyone wants to listen to this
recording in order to assess the problem, please drop me a mail and I'll
send the file.

Have a nice Sunday

73 de Glenn ON4WIX

----- Original Message -----
From: "John D'Ausilio" <[hidden email]>
To: "ON4WIX" <[hidden email]>
Sent: Sunday, April 09, 2006 5:41 AM
Subject: Re: [Elecraft] K2 s/n 5361 SSB TX audio problem

>I had a crappy audio issue that turned out to be RF getting into the
> audio .. there's some docs around that describe how to correctly
> ground the housing of the mic connector, you might want to try those.
>
> gl de w1rt/john
>
> On 4/8/06, ON4WIX <[hidden email]> wrote:
>> Hi all
>>
>> I'm experiencing a funny problem with my K2 s/n 5361.
>> My KSB2 board went through intitial testing without problems, all
>> measured values were OK as per the manual.
>> My TX audio however is horrible. It sounds very choppy (one ham reported
>> to me it sounds 'very restrained'), it seems like the signal is cutting
>> out and then switching back on in a very rapid fashion. I get almost no
>> ALC reading when modulating, neither speaking very closely into the
>> microphone nor a few inches away.
>> At first I thought I was experiencing the well-documented low mike gain
>> problem. When speaking very closely to the microphone (a Kenwood MC43)
>> the audio sounds reasonably clear (distorted but not much gets chopped
>> out) but as soon as I move away from the microphone the chopping effect
>> kicks in. This led me to believe that my mike output level was too low
>> and that the KSB2's noise gate was operating on its gating threshold.
>> I then connected a preamp between the mike and the K2. With the K2
>> connected to a dummy load I listened to my TX signal through my Kenwood
>> TS570. Varying the preamp gain made no noticeable difference, the audio
>> kept sounding distorted.
>> I then tried the R14 mod (changing the 1k R14 into a 10k resistor). No
>> solution, still very crappy audio (I disconnected my preamp at this
>> stage).
>> At that moment I discovered a funny thing: when speaking into the mike at
>> a distance of approximately 1 foot I noticed that my audio was almost
>> sounding natural. Of course I was not getting any power out of the K2
>> this way. When I moved the mike closer to my mouth the distortion quickly
>> came back.
>> So, at this moment it looks like I'm grossly overmodulating when I speak
>> at a normal distance from my mike. It sounds a lot better when I speak
>> far away from the mike but then I'm really running QRPp, hi.
>> I've taken the KSB2 board out of the K2 and checked all soldering joints
>> (which seem OK). One of T2's leads looked suspicious so I desoldered T2
>> and rewound it with the little spare wire I had left and resoldered it.
>> Still no luck.
>> Receive audio is OK so the filters seem do be doing fine.
>>
>> Any suggestions on where to start looking for the cause of this problem
>> are more than welcome.
>>
>> Thanks in advance
>>
>> Glenn ON4WIX
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>
>

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Don Wilhelm-3

RE: K2 s/n 5361 SSB TX audio problem

Glenn,

That certainly sounds like either you are overdriving the balanced
modulator, or there is a problem with the balanced modulator and/or the
carrier oscillator injection to the balanced modulator.

First, change R14 back to 1k - increasing it allows some low output mics to
work better, but it is best not to confuse thnigs with a non-standard value
in there.

If I recall, you have a 'scope - if so, it may be informative to take a look
at the DSB output from D4 to see if that looks clean.

Also, use Spectrogram to observe the passband of the OP1 filter in receive.
Be certain you have OP1 selected for the FL1 position and center the
passband between two markers set at 300 and 2600 Hz. If you do not have
Spectrogram already, you can download version 5 from Tom Hammond's website
www.n0ss.net
Refer to my website http://w3fpr.qrpradio.com article on K2 dial calibration
for much additional information about setting the K2 filters.

73,
Don W3FPR

> -----Original Message-----
>
> Thanks for your answer.
> I just grounded the mic jack housing following the guidelines I
> found on the
> Elecraft web site.
> No improvement however. I have tried different compressor settings (and
> bypassing it) but this does not improve or worsen the audio.
> When I hold the microphone about 1 foot from my mouth the audio
> seems OK but
> of course I'm not putting much power out. Moving the mike closer
> to my mouth
> the choppiness quickly becomes apparent. When I press my lips against the
> mike it sounds slightly better although rather distorted, a bit like the
> famous recording of the first man on the moon "A small step for man but a
> giant leap for mankind".
> I carried out my test on 40m. The thing that struck me also was
> that I got
> very little ALC reading, only 1 bar lighting up occasionally.
> That one LED
> didn't flicker along the rhythm of my modulation either. It just
> flickered
> on and off in a quick fashion and stayed lit for about half a
> second after I
> stopped talking.
> I recorded my test a few minutes ago. If anyone wants to listen to this
> recording in order to assess the problem, please drop me a mail and I'll
> send the file.
>
> Have a nice Sunday
>
> 73 de Glenn ON4WIX
>
> ----- Original Message -----
> From: "John D'Ausilio" <[hidden email]>
> To: "ON4WIX" <[hidden email]>
> Sent: Sunday, April 09, 2006 5:41 AM
> Subject: Re: [Elecraft] K2 s/n 5361 SSB TX audio problem
>
>
> >I had a crappy audio issue that turned out to be RF getting into the
> > audio .. there's some docs around that describe how to correctly
> > ground the housing of the mic connector, you might want to try those.
> >
> > gl de w1rt/john
> >
> > On 4/8/06, ON4WIX <[hidden email]> wrote:
> >> Hi all
> >>
> >> I'm experiencing a funny problem with my K2 s/n 5361.
> >> My KSB2 board went through intitial testing without problems, all
> >> measured values were OK as per the manual.
> >> My TX audio however is horrible. It sounds very choppy (one
> ham reported
> >> to me it sounds 'very restrained'), it seems like the signal
> is cutting
> >> out and then switching back on in a very rapid fashion. I get
> almost no
> >> ALC reading when modulating, neither speaking very closely into the
> >> microphone nor a few inches away.
> >> At first I thought I was experiencing the well-documented low
> mike gain
> >> problem. When speaking very closely to the microphone (a Kenwood MC43)
> >> the audio sounds reasonably clear (distorted but not much gets chopped
> >> out) but as soon as I move away from the microphone the
> chopping effect
> >> kicks in. This led me to believe that my mike output level was too low
> >> and that the KSB2's noise gate was operating on its gating threshold.
> >> I then connected a preamp between the mike and the K2. With the K2
> >> connected to a dummy load I listened to my TX signal through
> my Kenwood
> >> TS570. Varying the preamp gain made no noticeable difference,
> the audio
> >> kept sounding distorted.
> >> I then tried the R14 mod (changing the 1k R14 into a 10k resistor). No
> >> solution, still very crappy audio (I disconnected my preamp at this
> >> stage).
> >> At that moment I discovered a funny thing: when speaking into
> the mike at
> >> a distance of approximately 1 foot I noticed that my audio was almost
> >> sounding natural. Of course I was not getting any power out of the K2
> >> this way. When I moved the mike closer to my mouth the
> distortion quickly
> >> came back.
> >> So, at this moment it looks like I'm grossly overmodulating
> when I speak
> >> at a normal distance from my mike. It sounds a lot better when I speak
> >> far away from the mike but then I'm really running QRPp, hi.
> >> I've taken the KSB2 board out of the K2 and checked all
> soldering joints
> >> (which seem OK). One of T2's leads looked suspicious so I
> desoldered T2
> >> and rewound it with the little spare wire I had left and
> resoldered it.
> >> Still no luck.
> >> Receive audio is OK so the filters seem do be doing fine.
> >>
> >> Any suggestions on where to start looking for the cause of
> this problem
> >> are more than welcome.
> >>
> >> Thanks in advance
> >>
> >> Glenn ON4WIX
> >> _______________________________________________
> >> Elecraft mailing list
> >> Post to: [hidden email]
> >> You must be a subscriber to post to the list.
> >> Subscriber Info (Addr. Change, sub, unsub etc.):
> >> http://mailman.qth.net/mailman/listinfo/elecraft
> >>
> >> Help: http://mailman.qth.net/subscribers.htm
> >> Elecraft web page: http://www.elecraft.com
> >>
> >
> >
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
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