P3 SVGA interference -

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P3 SVGA interference -

Bob Lanning
In response to my message May 23, 2012; 3:27pm on the Elecraft P3
reflector Roger White W5RDW in Murphy, Texas responded off-list.  He had
the same problem I described.  It was not coming from the K3 but from
inside the P3.  We both noted it started after installing the SVGA.

During our investigation we boy found:

1 - the signal is about 5kHz wide
2 - it moves either up or down in frequency ever so slowly
3 - moving the VFO does not change the position of the signal - internal
to P3?
4 - reach back and approach the IF signal coax between the K3 & P3
causes it to temporarily go away
5 - sometimes touching the P3 cabinet caused it to disappear
6 - changed out the coax but it still happens

When the signal crosses the VFO frequency no sound is heard - only the
signal being listened to.  But reaching back in the proximity of the
linking coax causes it to go away.  Turning PC and other gear off has no
effect.

Roger and I spent sometime isolating the source.  We found a signal was
coupling into the IF cable inside the P3 from the ribbon cable.  As you
can see from the SVGA instruction manual the ribbon cable is so long
that if not dressed it goes across the P3 and pushes up against the IF
coax in the unit.

When the ribbon cable is dressed by folding it tightly keeping it well
away from the IF coax the wondering signal no longer appears.

If you are having this anomaly Roger and I recommend making the change
to the ribbon cable as shown in the two pictures below.  It would be
nice to have a shorter ribbon cable.

73,

Bob - W6OPO
Roger - W5RDW

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Re: P3 SVGA interference -

Arthur Burke
Is it possible the ribbon cable is as long as it is because it will need to
eventually be routed around something else to be added later?

Art - N4PJ



On Tue, May 29, 2012 at 2:10 AM, Bob Lanning <[hidden email]>wrote:

> In response to my message May 23, 2012; 3:27pm on the Elecraft P3
> reflector Roger White W5RDW in Murphy, Texas responded off-list.  He had
> the same problem I described.  It was not coming from the K3 but from
> inside the P3.  We both noted it started after installing the SVGA.
>
> During our investigation we boy found:
>
> 1 - the signal is about 5kHz wide
> 2 - it moves either up or down in frequency ever so slowly
> 3 - moving the VFO does not change the position of the signal - internal
> to P3?
> 4 - reach back and approach the IF signal coax between the K3 & P3
> causes it to temporarily go away
> 5 - sometimes touching the P3 cabinet caused it to disappear
> 6 - changed out the coax but it still happens
>
> When the signal crosses the VFO frequency no sound is heard - only the
> signal being listened to.  But reaching back in the proximity of the
> linking coax causes it to go away.  Turning PC and other gear off has no
> effect.
>
> Roger and I spent sometime isolating the source.  We found a signal was
> coupling into the IF cable inside the P3 from the ribbon cable.  As you
> can see from the SVGA instruction manual the ribbon cable is so long
> that if not dressed it goes across the P3 and pushes up against the IF
> coax in the unit.
>
> When the ribbon cable is dressed by folding it tightly keeping it well
> away from the IF coax the wondering signal no longer appears.
>
> If you are having this anomaly Roger and I recommend making the change
> to the ribbon cable as shown in the two pictures below.  It would be
> nice to have a shorter ribbon cable.
>
> 73,
>
> Bob - W6OPO
> Roger - W5RDW
>
> ______________________________________________________________
> 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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Re: P3 SVGA interference -

John Klewer
In reply to this post by Bob Lanning
There is (was) a known problem with the MMIC amplifier (comprising the IF amp
into the P3) oscillating.....this instability could certainly manifest itself in
what you are seeing.

The guys at Elecraft sent me a replacement rear panel interface board and my prob
went away

Also, make certain the coax connectors are well grounded to the rear panel with
the supplied star washers.

Hope this helps

John



On Tue May 29  5:15 , Arthur Burke  sent:

>Is it possible the ribbon cable is as long as it is because it will need to
>eventually be routed around something else to be added later?
>
>Art - N4PJ
>
>
>
>On Tue, May 29, 2012 at 2:10 AM, Bob Lanning [hidden email]>wrote:
>
>> In response to my message May 23, 2012; 3:27pm on the Elecraft P3
>> reflector Roger White W5RDW in Murphy, Texas responded off-list.  He had
>> the same problem I described.  It was not coming from the K3 but from
>> inside the P3.  We both noted it started after installing the SVGA.
>>
>> During our investigation we boy found:
>>
>> 1 - the signal is about 5kHz wide
>> 2 - it moves either up or down in frequency ever so slowly
>> 3 - moving the VFO does not change the position of the signal - internal
>> to P3?
>> 4 - reach back and approach the IF signal coax between the K3 & P3
>> causes it to temporarily go away
>> 5 - sometimes touching the P3 cabinet caused it to disappear
>> 6 - changed out the coax but it still happens
>>
>> When the signal crosses the VFO frequency no sound is heard - only the
>> signal being listened to.  But reaching back in the proximity of the
>> linking coax causes it to go away.  Turning PC and other gear off has no
>> effect.
>>
>> Roger and I spent sometime isolating the source.  We found a signal was
>> coupling into the IF cable inside the P3 from the ribbon cable.  As you
>> can see from the SVGA instruction manual the ribbon cable is so long
>> that if not dressed it goes across the P3 and pushes up against the IF
>> coax in the unit.
>>
>> When the ribbon cable is dressed by folding it tightly keeping it well
>> away from the IF coax the wondering signal no longer appears.
>>
>> If you are having this anomaly Roger and I recommend making the change
>> to the ribbon cable as shown in the two pictures below.  It would be
>> nice to have a shorter ribbon cable.
>>
>> 73,
>>
>> Bob - W6OPO
>> Roger - W5RDW
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: [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: [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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Re: P3 SVGA interference -

W5RDW
n6ax wrote
There is (was) a known problem with the MMIC amplifier (comprising the IF amp into the P3) oscillating.....this instability could certainly manifest itself in what you are seeing.
Wow, this could be what my problem has been. In my past years as a microwave engineer, I used many of the MMIC amps when they first came out and they were difficult to tame, as they have a ton of gain at very low frequencies (lower than what they were intended to be used). I can see this may be what my problem is (was), as the signal that was creeping across the screen was large in amplitude and shaking a bunch....(aka like an oscillation).

It looks like Elecraft has noted the problem. I may have temporarily solved my problem buy "finger tweaking" the assemblies by pushing, pressing, etc. but a more permanent solution will be needed eventually.
Roger W5RDW
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Re: P3 SVGA interference -

Bob - W6OPO
In reply to this post by John Klewer
I can agree with you regarding the IF oscillator oscillating since when I approach the coax it changes the conditions stopping the oscillatoin. BUT - if it was the P3's IF amplifier going into oscillation I would expect the display to freeze as no IF signal would be able to pass. That does not happen. The P3 and SVGA continue to operate as it should but has the extreneous signal displayed. I am convinced the ribbon cable signaling was inducing a signal onto the shield of the internal IF coax. Moving the ribbon cable away from the IF coax cleared the whole problem up. All is as it should be now. 73, Bob - W6OPO
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Re: P3 SVGA interference -

Bob - W6OPO
I just got a message from yet another P3 user who by moving the ribbon cable away from the internal IF coax removed the extraneous phantom signal.  He did NOT have the SVGA.

Elecraft - I suggest providing a shorter ribbon cable or a means to dress the cable in a straight line from front PCB to the SVGA board in the back.

73,

Bob - W6OPO
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Re: P3 SVGA interference -

Paul Saffren N6HZ
Hi Bob,

We're taking a look at it now.  A shorter ribbon cable is a possibility, but maybe there is a simple way to dress the existing cable by folding it and holding it with some sort of clip.  Just thinking out loud.

-Paul
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Re: P3 SVGA interference -

ke9uw
Thats what I did...dress the cable.

Sent from my iPad

On Jun 1, 2012, at 10:17 AM, "Paul Saffren N6HZ" <[hidden email]> wrote:

> Hi Bob,
>
> We're taking a look at it now.  A shorter ribbon cable is a possibility, but
> maybe there is a simple way to dress the existing cable by folding it and
> holding it with some sort of clip.  Just thinking out loud.
>
> -Paul
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/P3-SVGA-interference-tp7556731p7556922.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> 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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Chuck, KE9UW
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Re: P3 SVGA interference -

GARY-2
In reply to this post by Paul Saffren N6HZ
If I may make a suggestion Paul,
Among the many obvious solutions such as Velcro strapping or nylon ties
around the ribbon cable there's also the option of using a flat cable clip
or mount. An example is shown on this drawing from Panduit for their model
FCC-A clips;
< http://www.panduit.com/groups/MPM-GAWA/documents/PartDrawing/077542.pdf>
Since the ribbon cable is located close to the left side of the P3 housing
an adhesive flat cable clip easily holds the cable securely away from the
TMP coaxial cable on the right side of the cabinet. Another clip could be
used on the right side to hold the TMP cable further away from the ribbon
cable. In a pinch a short length of hook & loop material (Velcro) around the
ribbon cable seems to help also but I think the TMP cable needs to be
supported close to the righthand side of the cabinet with a clip or perhaps
a small adhesive tie mount and nylon tie.
Gary
N6LRV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Paul Saffren N6HZ
Sent: Friday, June 01, 2012 8:16 AM
To: [hidden email]
Subject: Re: [Elecraft] P3 SVGA interference -
Hi Bob,
We're taking a look at it now.  A shorter ribbon cable is a possibility, but
maybe there is a simple way to dress the existing cable by folding it and
holding it with some sort of clip.  Just thinking out loud.
-Paul

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Re: P3 SVGA interference -

Paul Saffren N6HZ
In reply to this post by Bob Lanning
I've found some adhesive clips that will allow the ribbon cable to be dressed along the left inside panel.  They should be available by the end of this week, by request, no charge (EPN: E980228). All future P3 kits and factory assembled units will be getting them as well.

Thanks for all your help and suggestions.

73,

Paul
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