Hello,

I got my Icom IC-R75 rx. connected to a Wellbrook ALA1530 loop antenna.
On this antenna, I have an enormous amount of 'buzzz' on much MW and SW
frequencies. It is much less noticeable on a portable receiver with a
whip antenna.
When I have just the center pin of the PL259 plug connected to the
receiver, much of the buzz disappears. As soon as I connect the other
part of the plug too (the shield of the coax, so to say), it becomes
audible again.
I am not very techinal, and don't know where to start troubleshooting.
Should I look for damage on the coax cable? Could it be badly
soldered/connected BNC plugs? Anything else that's worth investigating?

Many thanks for any tips!
--


73',


Mark Veldhuis.

On Thu, 28 Jul 2005 16:49:33 +0200, Mark Veldhuis
wrote:

When I have just the center pin of the PL259 plug connected to the
receiver, much of the buzz disappears. As soon as I connect the other
part of the plug too (the shield of the coax, so to say), it becomes
audible again.

Hi Mark,

Sounds like a ground loop. If you are using the Antenna Interface,
make all connections that give you this interference. Now, disconnect
the power lead to the Antenna Interface. If the noise goes away, you
have a ground loop that is associated with where your power to this
unit comes from, and what you are using as the ground for your
IC-R75.

73's
Richard Clark, KB7QHC

Hi,

In article ,
says...

Sounds like a ground loop. If you are using the Antenna Interface,
make all connections that give you this interference. Now, disconnect
the power lead to the Antenna Interface. If the noise goes away, you
have a ground loop that is associated with where your power to this
unit comes from, and what you are using as the ground for your
IC-R75.

I remember trying that before, and it did stop the noise indeed.
But... If it's a ground loop, wouldn't it be there all the time?
I'm asking because I came home tonight, connected the antenna, and...now
noise, no buzz! That too happened before, but the noise was back less
than half a day later.
So, could this still be a ground loop? And if so, how do I go about
getting rid of it? Is it an easy thing to do for someone non-technical
like me?

I am not using any ground for my R75 at the moment. With my previous
antenna setup, a longwire with MLB, I had a ground rod. And it did
absolutely nothing, it didn't make any difference at all...

Thanks for the help!
--


73',


Mark Veldhuis.

On Fri, 29 Jul 2005 04:41:27 +0200, Mark Veldhuis
wrote:

I remember trying that before, and it did stop the noise indeed.
But... If it's a ground loop, wouldn't it be there all the time?

Hi Mark,

Your experience indicates otherwise. This is not unusual. I've had
ground loops that depended on the weather. As it is frequently rainy
here (Seattle), my problems would come and go with the CHANGE in the
weather.

how do I go about
getting rid of it? Is it an easy thing to do for someone non-technical
like me?

Move the Interface power supply to the same outlet that you use to
power your R75. Check the ground of the AC socket and make sure your
wiring is not reversed (usually done with a small tester sold in most
hardware stores).

I am not using any ground for my R75 at the moment.

Unless you are running solely off batteries, have no other connections
to the R75 whatever, naturally you are connected to ground. You
simply don't know how it is getting to the R75 is all, and this is the
usual configuration of those who suffer from ground loops.

With my previous
antenna setup, a longwire with MLB, I had a ground rod. And it did
absolutely nothing, it didn't make any difference at all...

That's unusual to say the least. But it points out that whatever
ground you thought you had in the "ground rod" was simply duplicating
what already existed through the AC distribution system.

Another way to confirm is to replace the Interface power supply with a
battery pack.

73's
Richard Clark, KB7QHC

Your loop is sensitive to magnetic fields, such as might be produced by the
horizontal deflection system of a Television set or computer monitor, or by
a switching supply in a computer. The best way to minimize that problem is
to orient the loop to null out the interference. An additional way is to
move the loop as far away from likely sources of interference as possible.
Power the antenna and R75 from a car battery or portable DC source and take
them outside and roam around to see if you can find out where the noise is
coming from.

73, Chuck W6PKP

"Mark Veldhuis" wrote in message
...
Hi,

In article ,
says...

Sounds like a ground loop. If you are using the Antenna Interface,
make all connections that give you this interference. Now, disconnect
the power lead to the Antenna Interface. If the noise goes away, you
have a ground loop that is associated with where your power to this
unit comes from, and what you are using as the ground for your
IC-R75.

I remember trying that before, and it did stop the noise indeed.
But... If it's a ground loop, wouldn't it be there all the time?
I'm asking because I came home tonight, connected the antenna, and...now
noise, no buzz! That too happened before, but the noise was back less
than half a day later.
So, could this still be a ground loop? And if so, how do I go about
getting rid of it? Is it an easy thing to do for someone non-technical
like me?

I am not using any ground for my R75 at the moment. With my previous
antenna setup, a longwire with MLB, I had a ground rod. And it did
absolutely nothing, it didn't make any difference at all...

Thanks for the help!
--


73',


Mark Veldhuis.

Mark:

I have NEVER owned such a loop, and frankly, can't comment on its exact
workings.

However, the others seem to be suggesting, switch radio and loop to battery
power. Is the noise gone? If so, you have localized your problem. If not...

Shut off everything in the home (building, business, etc), is the noise gone?

If so, turn on things one at a time and locate the interference.

Frankly, I suspect I am wasting my text here, and you have already done this...

John

"Mark Veldhuis" wrote in message
...
Hello,

I got my Icom IC-R75 rx. connected to a Wellbrook ALA1530 loop antenna.
On this antenna, I have an enormous amount of 'buzzz' on much MW and SW
frequencies. It is much less noticeable on a portable receiver with a
whip antenna.
When I have just the center pin of the PL259 plug connected to the
receiver, much of the buzz disappears. As soon as I connect the other
part of the plug too (the shield of the coax, so to say), it becomes
audible again.
I am not very techinal, and don't know where to start troubleshooting.
Should I look for damage on the coax cable? Could it be badly
soldered/connected BNC plugs? Anything else that's worth investigating?

Many thanks for any tips!
--


73',


Mark Veldhuis.

Guys,

Thanks for your replies so far.
The buzz/noise is irregular. Not always, and when it's there, it's not
always audible on the same frequencies.
I am afraid it's something in the neighbourhood. Lots of houses around,
so it probably won't be easy to find out exactly where it comes from.
I also hear it when I connect a simple wire as an antenna, so I think
it's not a ground loop?
I made a recording of 1602 kHz. this afternoon. You can hear the
buzz/noise there, although not as strong as previous times.
Maybe someone can tell more by listening to the audioclip?
It is at http://mark-veldhuis.nl/1602.mp3 .

--


73',


Mark Veldhuis.

Mark Veldhuis wrote:
"The buz/noise is irregular."

A small battery operated portable containing a loop antenna will be
found to have a nulled response in a certain sense aimed toward the
interference source. Use it to find the source.

Best regards, Richard Harrison, KB5WZI

On Fri, 5 Aug 2005 14:55:33 +0200, Mark Veldhuis
wrote:
I made a recording of 1602 kHz. this afternoon. You can hear the
buzz/noise there, although not as strong as previous times.
Maybe someone can tell more by listening to the audioclip?
It is at http://mark-veldhuis.nl/1602.mp3 .

Hi Mark,

I listened several times and it sounds like white noise with maybe a
hint of programming. However, that is the problem with noise, hearing
"things." I would not call it buzz at all.

There also appear to be two weak and broad resonances, but this is
from the crude spectrum presented by the WinAmp display. I used to
have spectrum analyzer software that would give a waterfall display
that would be useful in this situation, but I no longer have it
installed.

That aside, it actually sounds quite normal except I would expect some
broadcast activity near that frequency there in the low country.

73's
Richard Clark, KB7QHC

Hi,

OK, 1 more clip. I know I could try to find the source of the noise by
using as portable radio + loop antenna, but my ALA is mounted on the
shed and I have no other loop available. Maybe someone can identify a
possible noise source by listening to the clip, or at least give more
tips. If not, I'll try to walk around the neighbourhood with just a
portable, and see what the results of that are.

The noise/buzz on this clip is stronger than on the previous one.

Thanks in advance!

http://www.mark-veldhuis.nl/audio.mp3

--


73',


Mark Veldhuis.