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Modulation interference KPA100

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Harry de Grood

Modulation interference KPA100

Hello,

I just finished the KPA100 without problems.
With the first test I hear that the sound of the modulation is not good, it
looks like a interference with a 50 Hz sound.
That is always, with 1 Watt output or 100 Watt output, it make's no
difference. My powersupply is good.
I check the alignment specialy the bias, that is good!
I was listning to the modulation with the KPA100 next to the K2 and
everything was normal.
Hear is the problem: With the KPA100 in the K2 the sound is bad!
What can I do? I check the cables, everything is normal.

Harry PA3CWQ.

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Dan Barker

RE: Modulation interference KPA100

How far from the K2 is the power supply? K2 is sensitive to magnetic fields.

Dan / WG4S / K2 #2456

<snip>
it looks like a interference with a 50 Hz sound.
</snip>
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Vic K2VCO

Re: Modulation interference KPA100

Dan Barker wrote:
> How far from the K2 is the power supply? K2 is sensitive to magnetic fields.

...and adding the KPA100 makes it more sensitive to them!
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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Don Wilhelm-3

RE: Modulation interference KPA100

In reply to this post by Harry de Grood

Harry,

Try a test - move the K2 4 to 5 feet away from anything that could possibly
contain a transformer and see if the 'modulation' goes away. If that
eliminates the modulation, you can either rearrange the shack so the
transformer fields are not close to the K2 or you can add the VCOSHLDKT
available from Elecraft.

73,
Don W3FPR

> -----Original Message-----
>
> I just finished the KPA100 without problems.
> With the first test I hear that the sound of the modulation is
> not good, it
> looks like a interference with a 50 Hz sound.
> That is always, with 1 Watt output or 100 Watt output, it make's no
> difference. My powersupply is good.
> I check the alignment specialy the bias, that is good!
> I was listning to the modulation with the KPA100 next to the K2 and
> everything was normal.
> Hear is the problem: With the KPA100 in the K2 the sound is bad!
> What can I do? I check the cables, everything is normal.
>
> Harry PA3CWQ.
>

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David A. Belsley

Re: Modulation interference KPA100

In reply to this post by Harry de Grood

Harry: Let me speculate. When the KPA100 is "next to" the K2, you
have it everything on your bench and away from the power supply. But
when you have the KPA100 "in the K2", you have returned everything to
the operating position, which is near the power supply. Obviously, I
could be very wrong in my speculation, but it sure sounds to me like
you're too near a linear power supply or other source of AC magnetic
field once you try the K2 with the KPA100 in place. Try moving it
away from the problem source.

best wishes,

dave belsley, w1euy

On Mar 27, 2006, at 3:14 PM, Harry de Grood wrote:

> Hello,
>
> I just finished the KPA100 without problems.
> With the first test I hear that the sound of the modulation is not
> good, it looks like a interference with a 50 Hz sound.
> That is always, with 1 Watt output or 100 Watt output, it make's no
> difference. My powersupply is good.
> I check the alignment specialy the bias, that is good!
> I was listning to the modulation with the KPA100 next to the K2 and
> everything was normal.
> Hear is the problem: With the KPA100 in the K2 the sound is bad!
> What can I do? I check the cables, everything is normal.
>
> Harry PA3CWQ.
>
>
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> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Elecraft web page: http://www.elecraft.com

Geoffrey Mackenzie-Kennedy-2

Re: Modulation interference KPA100

In reply to this post by Vic K2VCO

Vic K2VCO <[hidden email]> wrote:

> Dan Barker wrote:
>> How far from the K2 is the power supply? K2 is sensitive to magnetic
>> fields.
>
> ...and adding the KPA100 makes it more sensitive to them!

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

That's interesting Vic! Have you noticed this when the KPA100 is separated
from the K2, but with the interconnections between K2 and KPA100 in place?
Am wondering about things other than the VCO that could be affected by
external magnetic fields, and magnetic "circuits".

73,
Geoff
GM4ESD

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Don Wilhelm-3

RE: Modulation interference KPA100

Geoff,

I am just guessing here,but I would think the proximity of the KPA100 shield
would help to conduct the magnetic field and could lead to a greater flux
density near T5 and L30 than would be the case without the KPA100 installed.

Of course, all this is but interesting dialog and does not cure anything,
the fact remains that T5 and L30 are effected by magnetic fields - although
such discussion does help to promote better understanding.

73,
Don W3FPR

> -----Original Message-----

> Vic K2VCO <[hidden email]> wrote:
>
> > Dan Barker wrote:
> >> How far from the K2 is the power supply? K2 is sensitive to magnetic
> >> fields.
> >
> > ...and adding the KPA100 makes it more sensitive to them!
>
> ---------------------------------------------------------------------
>
> That's interesting Vic! Have you noticed this when the KPA100 is
> separated
> from the K2, but with the interconnections between K2 and KPA100
> in place?
> Am wondering about things other than the VCO that could be affected by
> external magnetic fields, and magnetic "circuits".
>
> 73,
> Geoff
> GM4ESD
>
>

Geoffrey Mackenzie-Kennedy-2

Re: Modulation interference KPA100

Don,

Yes, I would agree with all that. I must plead guilty to thinking about
other 'reactions' that might leave some small part of the 'magnetic' problem
remaining, probably not a very useful application of mental effort!

73,
Geoff
GM4ESD.

----- Original Message -----

> Geoff,
>
> I am just guessing here,but I would think the proximity of the KPA100
> shield
> would help to conduct the magnetic field and could lead to a greater flux
> density near T5 and L30 than would be the case without the KPA100
> installed.
>
> Of course, all this is but interesting dialog and does not cure anything,
> the fact remains that T5 and L30 are effected by magnetic fields -
> although
> such discussion does help to promote better understanding.
>
> 73,
> Don W3FPR
>