P3 - Ref Lvl

[k6dgw]

My P3 is new, I'm just getting used to it.  Quite suddenly today, the
leftmost third of the baseline noise started to rise upward.  Tuning
doesn't change it, it's still the leftmost 1/3.  Happens at any span
setting, and rises about half way up the scale.  It's sort of variable,
jumping up and down a bit and has the band noise on it just like it
normal if it was straight across the bottom.

I discovered that putting my hand on the top of the P3 anchored it back
to the bottom.  A clip lead from the IF Out BNC outer shell to the
station ground also anchored it solidly down.  The antenna coupler,
power supply, K3, and KPA500 are all grounded to the single copper strap
on the back of the shelf which is connected to a UFER ground directly
under the shack, and to the utility safety ground ["green wire"]  There
is no ground lug on the P3.

I would have thought the coax IF connection would have grounded the P3
chassis to the K3.  I'm wondering if I've got some grounding problem in
the P3.  It has worked fine since I built it and first turned it on and
this is the first time I've seen this anomaly.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org

anomaly [n. ahh-NAHM-ahh-lee]  A term used by NASA to describe any
unexpected or unplanned event or system state, regardless of severity.
It can range from a burned out indicator on a panel to the rocket
landing pointy-end down outside of Tucson.
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[Don Wilhelm-4]

Fred,

It sounds like you may want to check the coax to see if it is OK.

73,
Don W3FPR

On 9/16/2011 3:45 PM, Fred Jensen wrote:

> My P3 is new, I'm just getting used to it.  Quite suddenly today, the
> leftmost third of the baseline noise started to rise upward.  Tuning
> doesn't change it, it's still the leftmost 1/3.  Happens at any span
> setting, and rises about half way up the scale.  It's sort of variable,
> jumping up and down a bit and has the band noise on it just like it
> normal if it was straight across the bottom.
>
> I discovered that putting my hand on the top of the P3 anchored it back
> to the bottom.  A clip lead from the IF Out BNC outer shell to the
> station ground also anchored it solidly down.  The antenna coupler,
> power supply, K3, and KPA500 are all grounded to the single copper strap
> on the back of the shelf which is connected to a UFER ground directly
> under the shack, and to the utility safety ground ["green wire"]  There
> is no ground lug on the P3.
>
> I would have thought the coax IF connection would have grounded the P3
> chassis to the K3.  I'm wondering if I've got some grounding problem in
> the P3.  It has worked fine since I built it and first turned it on and
> this is the first time I've seen this anomaly.
>

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[k6dgw]

On 9/16/2011 9:44 PM, joe levy wrote:
> Hi Change the coax between the K3 and the P3 to another one (better a
> silver plated "old" one!). The coax supplied by EleCraft has some
> other plating and developes bad contact on the shield.(maybe Deoxit
> could help..)

Thanks.  Deoxit on both connectors seems to have "fixed" it.  I really
wish my P3 had a ground screw, just on general principles if for no
other reason.  I think I'll make up a piece of RG-58 with a BNC on one
end, and the braid pigtailed on the other and connected to my single
point ground.  I can then plug it into the IF OUT jack on the P3 for
grounding.

I'm fairly certain whatever is causing the problem is at the "far
display end" of the P3 receiver chain, the entire "receiver" part seems
to be unaffected, it's just the baseline.  Noise and signals go up the
little "baseline hill" just as they do when it's horizontal.  If you see
this, lay your hand on the top of the P3.  For me, that returned a
normal baseline.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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