RF noise on 80M with KPA500 plugged into AC outlet

[John Freed]

Here is an interesting situation.  On 80 meters (3.980 MHZ) the background noise goes from S7 to S9+20 when I plug the KPA500 into the AC outlet.  I have not turned on the Amplifier, just plugged it into the AC outlet.  I disconnect the power cord from the amplifier at the amplifier and the noise remains.  I unplug the power cord and the background noise drops back to S7.  This only happens on 80 meters.  I have an idea the outlet may have a grounding problem.  I will test it tomorrow.  Any ideas??

I have a ground bar that all of the radios are attached to.  Single ground wire to an 8 ft ground rod just outside the shack. Hmmmmm!  (me scratching my head)

72

John Freed, KX6F
ARES
Redcross DST
Flying Pigs
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[Jim Brown-10]

On Tue,10/4/2016 8:18 PM, John Freed wrote:
> Here is an interesting situation.  On 80 meters (3.980 MHZ) the background noise goes from S7 to S9+20 when I plug the KPA500 into the AC outlet.  I have not turned on the Amplifier, just plugged it into the AC outlet.  I disconnect the power cord from the amplifier at the amplifier and the noise remains.  I unplug the power cord and the background noise drops back to S7.  This only happens on 80 meters.  I have an idea the outlet may have a grounding problem.  I will test it tomorrow.
That's a good start.

> Any ideas??

Describe the antenna that you're listening to when this happens. How far
from the shack?  If it's any sort of end fed antenna, what is your
counterpoise?

Is this the "standard" line cord that came with the KPA500?  Is the KPA
wired for 120V or 240V? Are you sure the plug is correctly wired?  For
240V, the two "hot" wires must go between the two legs of 240V, the
equipment ground (green wire) must go to the green wire at the outlet,
and there must be NO connection to neutral.  For 120V, the transformer
must be wired to phase (120V hot) and neutral, the the equipment ground
must go to the green wire at the outlet, and there must be no connection
between neutral and the green wire.

> I have a ground bar that all of the radios are attached to.  Single ground wire to an 8 ft ground rod just outside the shack. Hmmmmm!  (me scratching my head)

Is that ground rod bonded to all other grounds in your home/building?  
It MUST be. Is there a good ground (driven rod) at the service entrance?

73, Jim K9YC
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[K9MA]

On 10/4/2016 22:18, John Freed wrote:
>   I disconnect the power cord from the amplifier at the amplifier and the noise remains.
Do you mean there's just a power cord plugged into the outlet, and the
other end connected to nothing?  If that's the case, I'd suspect arcing
at the plug at one end of the cord, in which case you should replace
that cord immediately, before it starts a fire.  The only other
possibility I can think of is that the wiring to the wall socket is in
conduit, so it's shielded, and the line cord is acting as an antenna,
radiating whatever junk is on the wiring.  (Be sure to turn off all the
fluorescent lights nearby.)

73,

Scott  K9MA


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Scott  K9MA

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[Bob Novas]

I would open up the power plug that goes into the wall socket and check its
wiring.  I suspect that plug is doing something bad with neutral and ground
- like maybe connecting them together.  Bob - W3DK

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of John
Freed
Sent: Tuesday, October 04, 2016 11:18 PM
To: [hidden email]
Subject: [Elecraft] RF noise on 80M with KPA500 plugged into AC outlet
Importance: High

Here is an interesting situation.  On 80 meters (3.980 MHZ) the background
noise goes from S7 to S9+20 when I plug the KPA500 into the AC outlet.  I
have not turned on the Amplifier, just plugged it into the AC outlet.  I
disconnect the power cord from the amplifier at the amplifier and the noise
remains.  I unplug the power cord and the background noise drops back to S7.
This only happens on 80 meters.  I have an idea the outlet may have a
grounding problem.  I will test it tomorrow.  Any ideas??

I have a ground bar that all of the radios are attached to.  Single ground
wire to an 8 ft ground rod just outside the shack. Hmmmmm!  (me scratching
my head)

72

John Freed, KX6F
ARES
Redcross DST
Flying Pigs
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If he is hearing the the cord radiate, he either has the antenna very
close to the shack or the coax is leaky.

John KK9A

From: K9MA k9ma at sdellington.us
Wed Oct 5 00:20:43 EDT 2016

The only other
possibility I can think of is that the wiring to the wall socket is in
conduit, so it's shielded, and the line cord is acting as an antenna,
radiating whatever junk is on the wiring.  (Be sure to turn off all the
fluorescent lights nearby.)

73,

Scott  K9MA


--
Scott  K9MA

k9ma at sdellington.us

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[Don Wilhelm]

John,

Is that ground rod connected with heavy copper wire (#6 or better #4) to
the Utility Entry ground rod?  If not, that may be the cause.
Even if it is not the cause of that behavior, it is a safety issue for
you and your family and is a requirement according to the National
Electrical Code.  The only exception is if the ground rods are more than
100 feet apart.

A power cord - connected only to the wall receptacle should not cause
any noise.
Try the same with another power cord - if the same thing happens,
examine your house wiring.  OTOH, if the other power cord does not
produce the noise, you may conclude that the original power cord has
some sort of leakage problem.

73,
Don W3FPR

On 10/4/2016 11:18 PM, John Freed wrote:
> Here is an interesting situation.  On 80 meters (3.980 MHZ) the background noise goes from S7 to S9+20 when I plug the KPA500 into the AC outlet.  I have not turned on the Amplifier, just plugged it into the AC outlet.  I disconnect the power cord from the amplifier at the amplifier and the noise remains.  I unplug the power cord and the background noise drops back to S7.  This only happens on 80 meters.  I have an idea the outlet may have a grounding problem.  I will test it tomorrow.  Any ideas??
>
> I have a ground bar that all of the radios are attached to.  Single ground wire to an 8 ft ground rod just outside the shack. Hmmmmm!  (me scratching my head)
>
>

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