P3 generates noise on 144 MHz

[Roger Crofts]

I recently installed the K144XV 2meter converter in my K3. I could work strong stations on 2m with no problem, but weak stations were swamped by noise which was S9 over the entire band. My P3 was showing that the noise consisted of carriers every 19KHz with lots of buzzy noise in-between. I soon found the source of the noise. It was the P3 !  When I turned the P3 power off, the noise completely disappeared. With the P3 on and the antenna replaced with a dummy load, the noise also all but disappeared. When I removed the RS232 cable and the IF cable from the P3, leaving only the power cable, the noise persisted at the same strength. So it appears that the P3 box is radiating this noise directly into my antenna. My antenna is a 2meter ground plane on the roof of my shack. It is about 8 feet from the P3. Obviously a solution would be to move my 2 meter antenna well away from the shack. I was not able to find any mention of this problem in the archives. Is there something wrong wi
 th my particular P3 or do they all do this?

Roger Crofts, VK4YB
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[K7MDL]

CONTENTS DELETED

The author has deleted this message.

[David Pratt]

I had a similar problem, Roger, and cured it completely by putting a
ferrite clamp-on on each end of the 12V power cable between the K3 and
the P3.  But YMMD

73 de David G4DMP

In a recent message, Roger Crofts <[hidden email]> writes
[snip]
> I could work strong stations on 2m with no problem, but weak stations
>were swamped by noise which was S9 over the entire band.
[snip]
--
 + - - - - - - - - - - - - - - - - +
 | David M Pratt, Kippax, Leeds.   |
 | Website: http://www.g4dmp.co.uk |
 + - - - - - - - - - - - - - - - - +

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[M0AFJ]

I'd be interested to see the EMC Test Report on the P3, required for selling into the EU and I think Australia, the P3 should not radiate emissions at this level and pass EN55022 or similar standards. Perhaps Elecraft could comment please?. I was thinking of picking up a P3 at Dayton but may hang fire...

As hams we have no right to complain about PLT, Plasma TV etc if we don't keep our own house in order.

Best regards, Tim Hague, MIET, MIEEE,
Skype m0afj.Tim
Sent on my iPad


On 10 Feb 2013, at 23:44, "Roger Crofts" <[hidden email]> wrote:

> I recently installed the K144XV 2meter converter in my K3. I could work strong stations on 2m with no problem, but weak stations were swamped by noise which was S9 over the entire band. My P3 was showing that the noise consisted of carriers every 19KHz with lots of buzzy noise in-between. I soon found the source of the noise. It was the P3 !  When I turned the P3 power off, the noise completely disappeared. With the P3 on and the antenna replaced with a dummy load, the noise also all but disappeared. When I removed the RS232 cable and the IF cable from the P3, leaving only the power cable, the noise persisted at the same strength. So it appears that the P3 box is radiating this noise directly into my antenna. My antenna is a 2meter ground plane on the roof of my shack. It is about 8 feet from the P3. Obviously a solution would be to move my 2 meter antenna well away from the shack. I was not able to find any mention of this problem in the archives. Is there something wrong
 wi

> th my particular P3 or do they all do this?
>
> Roger Crofts, VK4YB
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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[Stephen G4SJP]

I've had absolutely no issues with my P3 and a 2m ssb transceiver just
inches from it.  This will doubtless be the exception rather than the
rule.  There must be something not quite right somewhere.

73 Stephen G4SJP


On 11 February 2013 07:37, Tim Hague <[hidden email]> wrote:

> I'd be interested to see the EMC Test Report on the P3, required for
> selling into the EU and I think Australia, the P3 should not radiate
> emissions at this level and pass EN55022 or similar standards. Perhaps
> Elecraft could comment please?. I was thinking of picking up a P3 at Dayton
> but may hang fire...
>
> As hams we have no right to complain about PLT, Plasma TV etc if we don't
> keep our own house in order.
>
> Best regards, Tim Hague, MIET, MIEEE,
> Skype m0afj.Tim
> Sent on my iPad
>
>
> On 10 Feb 2013, at 23:44, "Roger Crofts" <[hidden email]> wrote:
>
> > I recently installed the K144XV 2meter converter in my K3. I could work
> strong stations on 2m with no problem, but weak stations were swamped by
> noise which was S9 over the entire band. My P3 was showing that the noise
> consisted of carriers every 19KHz with lots of buzzy noise in-between. I
> soon found the source of the noise. It was the P3 !  When I turned the P3
> power off, the noise completely disappeared. With the P3 on and the antenna
> replaced with a dummy load, the noise also all but disappeared. When I
> removed the RS232 cable and the IF cable from the P3, leaving only the
> power cable, the noise persisted at the same strength. So it appears that
> the P3 box is radiating this noise directly into my antenna. My antenna is
> a 2meter ground plane on the roof of my shack. It is about 8 feet from the
> P3. Obviously a solution would be to move my 2 meter antenna well away from
> the shack. I was not able to find any mention of this problem in the
> archives. Is there something wrong
>  wi
> > th my particular P3 or do they all do this?
> >
> > Roger Crofts, VK4YB
> > ______________________________________________________________
> > 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
> ______________________________________________________________
> 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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[Roger Crofts]

Thanks to everyone who responded. With your help, I have already reduced the noise level from S9+5db down to S6. The receiver noise floor is S3, so I still have a little way to go. There is now no doubt that the P3 power cord is responsible for most of the noise radiation. Putting the ferrite clamp-ons on the power cord as suggested by David, G4DMP, had the biggest effect. I also obtained a small improvement by removing some accessories that were sharing the 12V switched output from the K3. I am using the power cord supplied with the P3, but I had a splitter at the K3 end to feed power to a keyer and pre-amp. The extra cables for these devices were acting as additional antenna wires to radiate the 144MHz noise. However it seems to me that the noise should not be getting onto the P3 power cable in the first place. I looked at the P3 circuit diagram and was surprised to see that there is no series inductor in the power lead as it enters the box. Every other DC (or AF) connectio
 n I could find in the K3/P3 was protected by a series inductor and usually multiple bypass capacitors. There is a single bypass capacitor in the P3 power line. It is C500 with a value of 100nF. It seems to me that the effectiveness of this bypass capacitor very much depends upon a very good and direct connection between the I/O board printed circuit and the case. This connection relies on the 4 screws associated with the two 9pin D connectors. On re-reading the construction manual, I notice there is an instruction at the top of page 41, to check the surface of the metal work which mates with these connectors. At the time of construction I only gave this a cursory glance. I may have been remiss here. I will polish this surface with emery cloth and see if it makes any difference. I also tried powering the P3 from another 12Volt power supply, but the noise remained at S6. If I stretched the power cord in a certain direction the noise could be made to drop to the receiver noise
 floor (S3). I guess that this is because the power cord "antenna" has a null towards my 2 meter antenna in this particular arrangement. This is a solution, but not a very good one!  I will continue my experiments and let you know how they go.

Roger Crofts, VK4YB
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[John Lemay]

Roger

 

About a year ago when I was using my K3, K144XV and P3 combination I went
through most of the suggestions you have received . The noise floor was
reduced to almost satisfactory levels, but not quite.

 

Two further things occur to me: The DC cable to the P3 is just over a
quarter wave long on 2m, so making it a different length could help.
Secondly, I'm considering using a shielded cable (some cheap thin coax would
be OK because the current consumed by the P3 is low).

 

Regards

 

John G4ZTR

 

 

  _____  

From: [hidden email]
[mailto:[hidden email]] On Behalf Of Roger Crofts
Sent: 12 February 2013 00:10
To: elecraft reflector
Subject: Re: [Elecraft] P3 generates noise on 144 MHz

 

Thanks to everyone who responded. With your help, I have already reduced the
noise level from S9+5db down to S6. The receiver noise floor is S3, so I
still have a little way to go. There is now no doubt that the P3 power cord
is responsible for most of the noise radiation. Putting the ferrite
clamp-ons on the power cord as suggested by David, G4DMP, had the biggest
effect. I also obtained a small improvement by removing some accessories
that were sharing the 12V switched output from the K3. I am using the power
cord supplied with the P3, but I had a splitter at the K3 end to feed power
to a keyer and pre-amp. The extra cables for these devices were acting as
additional antenna wires to radiate the 144MHz noise. However it seems to me
that the noise should not be getting onto the P3 power cable in the first
place. I looked at the P3 circuit diagram and was surprised to see that
there is no series inductor in the power lead as it enters the box. Every
other DC (or AF) connectio
 n I could find in the K3/P3 was protected by a series inductor and usually
multiple bypass capacitors. There is a single bypass capacitor in the P3
power line. It is C500 with a value of 100nF. It seems to me that the
effectiveness of this bypass capacitor very much depends upon a very good
and direct connection between the I/O board printed circuit and the case.
This connection relies on the 4 screws associated with the two 9pin D
connectors. On re-reading the construction manual, I notice there is an
instruction at the top of page 41, to check the surface of the metal work
which mates with these connectors. At the time of construction I only gave
this a cursory glance. I may have been remiss here. I will polish this
surface with emery cloth and see if it makes any difference. I also tried
powering the P3 from another 12Volt power supply, but the noise remained at
S6. If I stretched the power cord in a certain direction the noise could be
made to drop to the receiver noise
 floor (S3). I guess that this is because the power cord "antenna" has a
null towards my 2 meter antenna in this particular arrangement. This is a
solution, but not a very good one!  I will continue my experiments and let
you know how they go.

Roger Crofts, VK4YB
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