P3 Double-humped Noise Monster

[Roger Crofts]

I am really happy I added the P3 to my K3. It is my window on the band. I can't imagine operating without it. I have had the P3 for six months now, but just recently it has started to display two big ugly humps of noise that drift across the display. This happens on all bands, but it might not appear for 20 minutes after switch-on. The double-humped noise monster is 30-40Khz wide and about -100 dBm level. When the antenna is disconnected the signals disappear but not the double-humped monster. There is no sound in the K3, so it looks like the noise monster is being generated within the P3. The frequency of the noise monster is incredibly sensitive to almost anything I do in the shack. It even shifts frequency if I put a few sheets of paper on top of the P3. If I put a book on top of the P3, the noise monster shifts completely off the screen (even with a 200KHz width). But it will drift back again later, whereupon I can remove the book and shift it again. This is a bit inconve
 nient, so can anybody tell me what is going on here?

73
Roger, VK4YB
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[k6dgw]

Hi Roger, summer here, winter there I guess ...

When I first got my P3, I had a similar observation.  Periodically, but
with no specific periodicity, the baseline would drift upward.  Putting
my hand on the top of the case sent it down.  At some point, I had the
scan at 200 KHz and realized it was some sort of "noise" that drifted
through and with smaller scan ranges, it looked like the drifting baseline.

My neighbor has a plasma TV, and at small scan ranges, it looks like
noise.  At 200 KHz, I can clearly see the spectrum and see it change as
the picture changes.  That's coming in through the K3 of course.

I finally took my P3 apart, carefully sanded the contact points [some
paint overspray there], and along the edges that were painted, put a
drop of DeOxit on each contact pad, and reassembled it, making sure ALL
the screws were truly tight.  Haven't had the problem since.

I think the P3 is a very high gain receiver, and is easily susceptible
to extraneous signals.    Making sure the case was electrically intact
made a huge difference.

I had some signals I couldn't tune to [they moved as I tuned], Elecraft
sent me a new cable with the condition that I cut the old one up into
small pieces in the trash.  That solved that one.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org

On 8/15/2013 4:55 PM, Roger Crofts wrote:

> I am really happy I added the P3 to my K3. It is my window on the
> band. I can't imagine operating without it. I have had the P3 for six
> months now, but just recently it has started to display two big ugly
> humps of noise that drift across the display. This happens on all
> bands, but it might not appear for 20 minutes after switch-on. The
> double-humped noise monster is 30-40Khz wide and about -100 dBm
> level. When the antenna is disconnected the signals disappear but not
> the double-humped monster. There is no sound in the K3, so it looks
> like the noise monster is being generated within the P3. The
> frequency of the noise monster is incredibly sensitive to almost
> anything I do in the shack. It even shifts frequency if I put a few
> sheets of paper on top of the P3. If I put a book on top of the P3,
> the noise monster shifts completely off the screen (even with a
> 200KHz width). But it will drift back again later, whereupon I can
> remove the book and shift it again. This is a bit inconve nient, so
> can anybody tell me what is going on here?

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[Andy Wood]

Hi Roger,

I had something similar with my P3. After cleaning the internal metal to metal contact points on the case, my problem disappeared. Good bonding (and tight screws) on all enclosure panels is essential.

I also had another problem with wandering "spikes" on the display. It turns out my BNC lead was faulty.

Andy  VK4KY