Spoke too soon... K2 problem

[Stephanie Maks]

Well I was too quick when I said I was done.

I've got a problem in my K2 that is really noticable in CW, although  
it is there in all modes.  When tuning a CW or plain carrier signal,  
instead of getting just a single pure tone, there is a second tone in  
there modulating with the original one.  It makes the CW tones sound  
like a buzz instead of what they should sound like.

With both the K1 an K2 side by side, both of them plugged into dummy  
loads, I can turn on my XG2 and move it near the two dummy loads, and  
on the K1 it sounds like it should, a single pure tone, like a bell.  
On the K2 it sounds like a raspy buzz.  What's worse is when I key  
the K2, the CW it is sending has that same raspy buzz in it, sounds  
terrible on the K1.

The second tone 'follows' the frequency tuned, what I mean is if I  
tune up 50 or 100 Hz from the XG2 signal, so the pitch goes up, it's  
a higher-pitched buzz, and likewise if I tune down 50 or 100 Hz it's  
a lower pitched buzz - not two distinct tones.

I have to sheepishly admit that I heard it when I did the 40M  
receiver test, back in alignment part 2.  It was about 1 or 2 am and  
I was using the XG2 as a signal source, and I heard the raspy sound  
and I assumed that my XG2's battery was dying and making it oscillate  
wierd.  I never thought to check if the XG2 was working properly and  
that the fault might be in the K2.

So, I know the fault must lie in something that was installed before  
the end of RF board assembly step 2, that is common to both transmit  
and receive.

Any suggestions as to where to look, based on these symptoms, would  
be most appreciated.

Thanks and 73 de Stephanie
va3uxb
K2 # 5311 / K1 # 2132



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[Vic K2VCO]

Stephanie Maks wrote:

> I've got a problem in my K2 that is really noticable in CW, although  it
> is there in all modes.  When tuning a CW or plain carrier signal,  
> instead of getting just a single pure tone, there is a second tone in  
> there modulating with the original one.  It makes the CW tones sound  
> like a buzz instead of what they should sound like.

Make sure the K2 is at least 18" (46 cm) away from any strong magnetic
field such as a linear power supply, an antenna rotor control, etc.  If
you have yours sitting on top of a big Astron power supply, for example,
you will get exactly what you are describing!
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Joseph Reed-2]

That is curious,  have you looked at the list archive?  I did a quick look and there are a number of hits that make reference to L30 and magnetic coupling.  Are you doing this on a power supply or a battery?
   
  I think the vco shielding mod also addresses this issue.
   
  Good luck,
   
  Joe N9JR

Stephanie Maks <[hidden email]> wrote:
  Well I was too quick when I said I was done.

I've got a problem in my K2 that is really noticable in CW, although
it is there in all modes. When tuning a CW or plain carrier signal,
instead of getting just a single pure tone, there is a second tone in
there modulating with the original one. It makes the CW tones sound
like a buzz instead of what they should sound like.

With both the K1 an K2 side by side, both of them plugged into dummy
loads, I can turn on my XG2 and move it near the two dummy loads, and
on the K1 it sounds like it should, a single pure tone, like a bell.
On the K2 it sounds like a raspy buzz. What's worse is when I key
the K2, the CW it is sending has that same raspy buzz in it, sounds
terrible on the K1.

The second tone 'follows' the frequency tuned, what I mean is if I
tune up 50 or 100 Hz from the XG2 signal, so the pitch goes up, it's
a higher-pitched buzz, and likewise if I tune down 50 or 100 Hz it's
a lower pitched buzz - not two distinct tones.

I have to sheepishly admit that I heard it when I did the 40M
receiver test, back in alignment part 2. It was about 1 or 2 am and
I was using the XG2 as a signal source, and I heard the raspy sound
and I assumed that my XG2's battery was dying and making it oscillate
wierd. I never thought to check if the XG2 was working properly and
that the fault might be in the K2.

So, I know the fault must lie in something that was installed before
the end of RF board assembly step 2, that is common to both transmit
and receive.

Any suggestions as to where to look, based on these symptoms, would
be most appreciated.

Thanks and 73 de Stephanie
va3uxb
K2 # 5311 / K1 # 2132



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[Roger Marrotte]

Steephanie,

Also check for an open with RFC15 on the bottom of the main board.  The
leads are easy to break inside.  I did it and had the same symptoms.  If
it's open (unsolder one end to check with an ohm meter) you can run without
it until you get a replacement.  That's what I did and I was REAL careful
putting the replacement in.  Works like a chemp now.

Roger, W1EM

Subject: [Elecraft] Spoke too soon... K2 problem


Well I was too quick when I said I was done.

I've got a problem in my K2 that is really noticable in CW, although  
it is there in all modes.  When tuning a CW or plain carrier signal,  
instead of getting just a single pure tone, there is a second tone in  
there modulating with the original one.  It makes the CW tones sound  
like a buzz instead of what they should sound like.

With both the K1 an K2 side by side, both of them plugged into dummy  
loads, I can turn on my XG2 and move it near the two dummy loads, and  
on the K1 it sounds like it should, a single pure tone, like a bell.  
On the K2 it sounds like a raspy buzz.  What's worse is when I key  
the K2, the CW it is sending has that same raspy buzz in it, sounds  
terrible on the K1.

The second tone 'follows' the frequency tuned, what I mean is if I  
tune up 50 or 100 Hz from the XG2 signal, so the pitch goes up, it's  
a higher-pitched buzz, and likewise if I tune down 50 or 100 Hz it's  
a lower pitched buzz - not two distinct tones.

I have to sheepishly admit that I heard it when I did the 40M  
receiver test, back in alignment part 2.  It was about 1 or 2 am and  
I was using the XG2 as a signal source, and I heard the raspy sound  
and I assumed that my XG2's battery was dying and making it oscillate  
wierd.  I never thought to check if the XG2 was working properly and  
that the fault might be in the K2.

So, I know the fault must lie in something that was installed before  
the end of RF board assembly step 2, that is common to both transmit  
and receive.

Any suggestions as to where to look, based on these symptoms, would  
be most appreciated.

Thanks and 73 de Stephanie
va3uxb
K2 # 5311 / K1 # 2132


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[Ron D'Eau Claire-2]

Adding to what Vic already reported, high-intensity desk lamps are another
cause of that. There's a transformer inside the base! It usually needs to be
closer to the rig than a power supply, but they are usually quite small and
so easy to set within range!

Ron AC7AC

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[Don Wilhelm-3]

Stephanie,

Vic and Roger already gave you the two best answers for the potential cause.
Check RFC15 with an ohmmeter first (do not depend on a test which checks the
voltage on each end of RFC15 - the voltage can read the same and it still
can be open).

If RFC15 is OK, then start looking for whatever things could cause magnetic
coupling into the cores of T5 and L30. Move the K2 as far away from
transformers as possible is the best solution - Elecraft does have an
optional kit to magnetically shield T5 should you find that is the only
solution.

73,
Don W3FPR

> -----Original Message-----
>
> I've got a problem in my K2 that is really noticable in CW, although
> it is there in all modes.  When tuning a CW or plain carrier signal,
> instead of getting just a single pure tone, there is a second tone in
> there modulating with the original one.  It makes the CW tones sound
> like a buzz instead of what they should sound like.
>
>

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[Stephanie Maks]

Ok...what's the Q-code for 'feeling like a dummy'?

Thank you everybody for pointing out the very obvious source of my  
problem.  I had read about what can happen with low quality power  
supplies.

The PS worked great with the K1...so I thought it would be ok with  
the K2.

I switched to battery and it sounds just great.

Thanks again everyone!

73 de Stephanie
va3uxb
K2 # 5311 / K1 # 2132



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[Ron D'Eau Claire-2]

Stephanie, VA3UXB, wrote:

Ok...what's the Q-code for 'feeling like a dummy'?

Thank you everybody for pointing out the very obvious source of my  
problem.  I had read about what can happen with low quality power  
supplies.

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

I think it's "QOOPS" <g>.

It's not a sign of a "low quality" supply at all, but merely one that has a
transformer in it. The "cheap" supplies to watch out for are the low-cost
"switching" supplies. They have a very small transformer that won't out put
much of a magnetic field to bother the K2, but have a tendency to generate a
lot of RF interference across the band. (High quality switching supplies
don't do either)

A "linear" supply using a sizeable transformer working at the 60 Hz mains
frequency does not produce RF interference, but does produce a large
magnetic field that can cause some problems like you experienced.

My big linear Astron sits on a stool under the operating desk where it
doesn't clutter up the operating table and where it's well away from the
rig.

Ron AC7AC

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[Stephanie Maks]

Hi Ed,

It's a Radio Shack 13.5 volt, 1-amp supply.  I was using it mainly  
for receive and test transmitting, up to about 2 or 3 watts, for  
which it worked great with the K1.

For what it's worth, the supply has a good long cord, two of them  
actually, about 6 feet of cord from the outlet to the supply itself,  
then another 6 feet from the power supply to the radio.  The supply  
was never anywhere near the K2.  However, my work bench is a pretty  
busy place, so there is a lot of other electrical equipment within 2  
or 3 feet of the radio.

On the other hand, I built my K2 with the magnetic VCO shield option  
right from the start, so I never bothered to instal L30.  So I'm not  
sure if the problem was magnetic interference.  I suspect that the  
the DC coming out of the power supply isn't as clean as I expected.

Anyhow, running it off some batteries did seem to clear up the  
receive 100%.  To be sure though, I'm having another good look at the  
K2 to make sure I didn't miss or mess up any of the RF chokes.

73 de Stephanie
va3uxb
K2#5311 - K1#2132


On 22-Jan-2006, at 11.41.40, Ed Findley wrote:

> Stephanie
> Just so we know so we can using it, What was the power supply you  
> were using
> that caused the problem?
> Thanks
>
> Ed Findley N5LDY
> K2 #1073 FP #1233
>
> Thank you everybody for pointing out the very obvious source of my
> problem.  I had read about what can happen with low quality power
> supplies.
>
>
>

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