Earth loop somewhere- humming sound
 

Hi,

I couldn't find any better Newsgroup to ask this question.
It's about a TV antenna.
When I try to capture a video from a VCR (the VCR is connected to the
antenna), I get a humming audio signal.
When I unplug the aerial cable, it's gone.
The antenna is installed on the roof and is proper earthed. In between
is a booster. I don't know if the booster causes the trouble but it
shouldn't.

The humming sound is only there when the VCR is connected to the PC (via
firewire) and the aerial cable is plugged into the VCR.

Any tips how to solve the problem would be greatly appreciated.

73
Gerhard Beulke
VK-DG1EHK


--

Looking for a dream holiday?
http://www.palmcove.net/
Palm Cove- Winner of the Award "Australia's Cleanest Beach"

On Sat, 10 Apr 2004 01:56:02 +1000, Gerhard Beulke
wrote:

Hi,

I couldn't find any better Newsgroup to ask this question.
It's about a TV antenna.
When I try to capture a video from a VCR (the VCR is connected to the
antenna), I get a humming audio signal.
When I unplug the aerial cable, it's gone.
The antenna is installed on the roof and is proper earthed. In between
is a booster. I don't know if the booster causes the trouble but it
shouldn't.

The humming sound is only there when the VCR is connected to the PC (via
firewire) and the aerial cable is plugged into the VCR.

Any tips how to solve the problem would be greatly appreciated.

73
Gerhard Beulke
VK-DG1EHK

Hi Gerhard,

One way that is quick, but not always effective, is to put a "ground
breaker" between your equipment's power supply and the mains. I'm not
sure if this is available for European AC connectors.

Another way is to use extension cords so all equipment that is powered
connects to the same mains outlet.

You say the antenna is "properly grounded." This is suspicious. Does
it have a wire going to the SAME ground (earth) connection as the
mains? If not, then connect the two together. If the first two don't
work (and even if they do), your problem is probably from this "proper
ground." The reason for the name "ground loop" is that you have two
different paths to ground (two different ground connections separated
by earth).

73's
Richard Clark, KB7QHC

In article ,
says...
Hi Gerhard,

One way that is quick, but not always effective, is to put a "ground
breaker" between your equipment's power supply and the mains. I'm not
sure if this is available for European AC connectors.

Another way is to use extension cords so all equipment that is powered
connects to the same mains outlet.

You say the antenna is "properly grounded." This is suspicious. Does
it have a wire going to the SAME ground (earth) connection as the
mains? If not, then connect the two together. If the first two don't
work (and even if they do), your problem is probably from this "proper
ground." The reason for the name "ground loop" is that you have two
different paths to ground (two different ground connections separated
by earth).

73's
Richard Clark, KB7QHC

Hi Richard,

I put an earth wire between the shield of the areal cable and the earth
of the powerpoint which fixed it.

Cheers


--

Looking for a dream holiday?
http://www.palmcove.net/
Palm Cove- Winner of the Award "Australia's Cleanest Beach"

On Sun, 11 Apr 2004 09:44:05 +1000, Gerhard Beulke
wrote:

Hi Richard,

I put an earth wire between the shield of the areal cable and the earth
of the powerpoint which fixed it.

Cheers

Hi Gerhard,

Sehr gut!

73's
Richard Clark, KB7QHC

On Sun, 11 Apr 2004 09:44:05 +1000, Gerhard Beulke
wrote:


I put an earth wire between the shield of the areal cable and the earth
of the powerpoint which fixed it.


Ausgezeichnet!


Bob, W9DMK, Dahlgren, VA
http://www.qsl.net/w9dmk

En Gerhard Beulke va escriure en Sat, 10 Apr 2004 01:56:02 +1000:

When I try to capture a video from a VCR (the VCR is connected to the
antenna), I get a humming audio signal.
When I unplug the aerial cable, it's gone.
The antenna is installed on the roof and is proper earthed. In between
is a booster. I don't know if the booster causes the trouble but it
shouldn't.

The humming sound is only there when the VCR is connected to the PC (via
firewire) and the aerial cable is plugged into the VCR.

Any tips how to solve the problem would be greatly appreciated.

Hi,

In this page:

http://www.jensentransformers.com/apps_wp.html

Look at this document:

http://www.jensentransformers.com/an/ts_guide.pdf

Of course they try to sell you their solutions, but the problem-
finding methodology and some solving tips are very good.

Toni

On Tue, 13 Apr 2004 16:47:37 +0200, Toni wrote:

Hi,

In this page:

http://www.jensentransformers.com/apps_wp.html

Look at this document:

http://www.jensentransformers.com/an/ts_guide.pdf

Of course they try to sell you their solutions, but the problem-
finding methodology and some solving tips are very good.

Toni

Hi Toni,

Good references. The products they would sell would be very useful as
some problems fail other resolutions (Gerhard was lucky). Myself, I
have a Mains isolation transformer for my floating battery charger
(and batteries) which powers my equipment. For me, Ground is at the
Antenna connector output (actually a threaded stub nearby) and not
both there and through the third wire. I also have isolation
transformers for the audio signal that goes off to my 'puter.

73's
Richard Clark, KB7QHC

Richard Clark wrote in message
...
On Tue, 13 Apr 2004 16:47:37 +0200, Toni wrote:

Hi,

In this page:

http://www.jensentransformers.com/apps_wp.html

Look at this document:

http://www.jensentransformers.com/an/ts_guide.pdf

Of course they try to sell you their solutions, but the problem-
finding methodology and some solving tips are very good.

Toni

Hi Toni,

Good references. The products they would sell would be very useful as
some problems fail other resolutions (Gerhard was lucky). Myself, I
have a Mains isolation transformer for my floating battery charger
(and batteries) which powers my equipment. For me, Ground is at the
Antenna connector output (actually a threaded stub nearby) and not
both there and through the third wire. I also have isolation
transformers for the audio signal that goes off to my 'puter.

73's
Richard Clark, KB7QHC

Isolating the equipment from normal power ground and establishing a new
common ground point was a common practice in the computer industry some
years ago. The high end stuff had triple shielded iso-transformers. The
first shield was connected to the AC neutral. A sort-of ground, but probably
useful in allowing shield capacitive current to be returned to the neutral
and avoid tripping GFI protected circuits. The second shield was connected
to building power ground (the "green wire") and only needed to deal with
potentials between neutral and ground, hopefully fairly low The third shield
was the "isolated ground" common point, connected to the equipment ground,
secondary neutral, and a local "earth" ground (building steel, etc.)