K3: cw xmiting 2 signals 600hz apart: HELP

[DOUGLAS ZWIEBEL]

Hi everybody...

I local K3 owner received this memo and forwarded it to me this
morning for my opinion:

<When you were working HA5JI, you had a side band about s6 up about
600 Hz.  I did not check the down side. Your main signal was s9+20.>

I was at work so I said I would listen when I got home (we live about
3 miles apart).

On 160m (where he got the notice), his signal sounded fine barefoot,
but with the amp on, I could hear it also.  So I asked him to qsy to
40m where he is about 25db over 9 on my K3.  And as I tuned off of
him, I could hear the "second signal" as described above.  The 2nd
signal tunes in the same direction as the real signal (it is not blow
by).

Any comments or even better, any suggestions for him?

Thanks,
Doug KR2Q
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[Steve Ellington]

Ive seen this several times on other rigs, not the K3. In a couple of
instances it turned out to be low DC supply voltage. Be sure it's 13.8V.
Good luck. 73
Steve Ellington
[hidden email]
----- Original Message -----
From: "DOUGLAS ZWIEBEL" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Friday, February 20, 2009 4:58 PM
Subject: [Elecraft] K3: cw xmiting 2 signals 600hz apart: HELP

> Hi everybody...
>
> I local K3 owner received this memo and forwarded it to me this
> morning for my opinion:
>
> <When you were working HA5JI, you had a side band about s6 up about
> 600 Hz.  I did not check the down side. Your main signal was s9+20.>
>
> I was at work so I said I would listen when I got home (we live about
> 3 miles apart).
>
> On 160m (where he got the notice), his signal sounded fine barefoot,
> but with the amp on, I could hear it also.  So I asked him to qsy to
> 40m where he is about 25db over 9 on my K3.  And as I tuned off of
> him, I could hear the "second signal" as described above.  The 2nd
> signal tunes in the same direction as the real signal (it is not blow
> by).
>
> Any comments or even better, any suggestions for him?
>
> Thanks,
> Doug KR2Q
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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[Geoffrey Mackenzie-Kennedy]

Hi Doug,

This certainly happens with the K2.

The cause in the K2 case is that the CW sidetone oscillator signal gets into
the VCO's varicap circuit and frequency modulates the VCO. The sidebands
that I can see coming from my K2 in CW mode are symmetrical above and below
carrier, one pair about 90db below carrier and the others much lower in
amplitude. Their level varies with band.

73,
Geoff
GM4ESD


DOUGLAS ZWIEBEL wrote:

> Hi everybody...
>
> I local K3 owner received this memo and forwarded it to me this
> morning for my opinion:
>
> <When you were working HA5JI, you had a side band about s6 up about
> 600 Hz.  I did not check the down side. Your main signal was s9+20.>
>
> I was at work so I said I would listen when I got home (we live about
> 3 miles apart).
>
> On 160m (where he got the notice), his signal sounded fine barefoot,
> but with the amp on, I could hear it also.  So I asked him to qsy to
> 40m where he is about 25db over 9 on my K3.  And as I tuned off of
> him, I could hear the "second signal" as described above.  The 2nd
> signal tunes in the same direction as the real signal (it is not blow
> by).
>
> Any comments or even better, any suggestions for him?
>
> Thanks,
> Doug KR2Q

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[Jan Erik Holm]

My findings are be sure to run as high voltage to K3
as possible. Per the manual 15V is the stipulated
maximum, run K3 at 14.9V and make sure you have no
voltage drop in the cable between K3 and PS. This
will give you the best TX performance in respect
to IMD.

/ Jim SM2EKM
--------------
Steve Ellington wrote:

> Ive seen this several times on other rigs, not the K3. In a couple of
> instances it turned out to be low DC supply voltage. Be sure it's 13.8V.
> Good luck. 73
> Steve Ellington
> [hidden email]
> ----- Original Message -----
> From: "DOUGLAS ZWIEBEL" <[hidden email]>
> To: "Elecraft Reflector" <[hidden email]>
> Sent: Friday, February 20, 2009 4:58 PM
> Subject: [Elecraft] K3: cw xmiting 2 signals 600hz apart: HELP
>
>
>> Hi everybody...
>>
>> I local K3 owner received this memo and forwarded it to me this
>> morning for my opinion:
>>
>> <When you were working HA5JI, you had a side band about s6 up about
>> 600 Hz.  I did not check the down side. Your main signal was s9+20.>
>>
>> I was at work so I said I would listen when I got home (we live about
>> 3 miles apart).
>>
>> On 160m (where he got the notice), his signal sounded fine barefoot,
>> but with the amp on, I could hear it also.  So I asked him to qsy to
>> 40m where he is about 25db over 9 on my K3.  And as I tuned off of
>> him, I could hear the "second signal" as described above.  The 2nd
>> signal tunes in the same direction as the real signal (it is not blow
>> by).
>>
>> Any comments or even better, any suggestions for him?
>>
>> Thanks,
>> Doug KR2Q

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[Vic K2VCO]

Geoffrey Mackenzie-Kennedy wrote:
> Hi Doug,
>
> This certainly happens with the K2.
>
> The cause in the K2 case is that the CW sidetone oscillator signal gets into
> the VCO's varicap circuit and frequency modulates the VCO. The sidebands
> that I can see coming from my K2 in CW mode are symmetrical above and below
> carrier, one pair about 90db below carrier and the others much lower in
> amplitude. Their level varies with band.

I had a bad case of this with my K2 and fixed it by replacing the quad DAC IC.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Geoffrey Mackenzie-Kennedy]

Vic K2VCO wrote on Saturday, February 21, 2009 3:32 PM

>> The cause in the K2 case is that the CW sidetone oscillator signal gets
>> into the VCO's varicap circuit and frequency modulates the VCO. The
>> sidebands that I can see coming from my K2 in CW mode are symmetrical
>> above and below carrier, one pair about 90db below carrier and the others
>> much lower in amplitude. Their level varies with band.
>
> I had a bad case of this with my K2 and fixed it by replacing the quad DAC
> IC.

-------------------------------------

Hi Vic,

I tried that with my K2, and it should have made some difference, but maybe
the quad DACs that I bought fell off the back of a truck. So I have not
bothered to do anything more because the sidebands are so far down, and not
heard by anyone that I have asked to check when signals are S9+.

This question was asked by Doug about K3s, but I thought that I would
mention the K2 in case the K3's sidetone signal does something similar.

73,
Geoff
GM4ESD

 

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