I've got a few PC's in nice metal cases. I can actually run most of my
receivers near the PC without too much problem, as long as the receiver is
powered by batteries. But the instant I hook my sound card to the receiver,
or I run the receiver off of AC power, all the SW bands are filled with
S9 hash generated by the computer and network equipment.

What's the most economical and reasonable way to deal with this? Will
RFC's on the power, ground, and sound lines be good enough? Those snap-
together ferrite cores from Radio Shack help a little, but not
nearly enough. In a few weeks my computer-controlled TenTec
RX-320D arrives and I want everything to be in ship-shape by then.

The computer equipment isn't "just a computer". It's several PC's,
an Ethernet hub, a DSL router, a UPS, etc. By experimenting I've discovered
that the computers themselves aren't so bad... but the networking
stuff (a necessity, I'm afraid) is abysmal.

The situation is serious enough that I'm seriously looking into optical
fiber links... anyone have advice for a low-budget solution that way?
If I can put the RX-320D upstairs away from all the Computer stuff, and
run the audio and RS-232 over optical fiber, I'd be in heaven. While
I know where to start for RS-232 over fiber, I don't know anything
about the available audio-over-fiber options.

Tim.

On 14 Sep 2003 09:38:09 -0700, (Tim Shoppa)
wrote:

I've got a few PC's in nice metal cases. I can actually run most of my
receivers near the PC without too much problem, as long as the receiver is
powered by batteries. But the instant I hook my sound card to the receiver,
or I run the receiver off of AC power, all the SW bands are filled with
S9 hash generated by the computer and network equipment.

What's the most economical and reasonable way to deal with this? Will
RFC's on the power, ground, and sound lines be good enough? Those snap-
together ferrite cores from Radio Shack help a little, but not
nearly enough. In a few weeks my computer-controlled TenTec
RX-320D arrives and I want everything to be in ship-shape by then.

I have a long 1/8" M-F extension cord from my line-in on my computer
to my radios... had the same problem. Cutting the female connector
off the end of the extension cord and soldering another one on but
leaving the shield off solved most of the problem. This broke the
ground loop.

If that does not work, and since Radio Shack stuff is normally
readilly available, they sell a Ground LP Isolator (270-0054) that
should do the trick or you can roll your own using their isolation
transformer (273-1374) which is $4.


73's and Cheers,
H Johnson

===========================================
H Johnson
KG4WOU
Member of the Madison County ARES,
Huntsville-Madison County EMA RACES,
and SKYWARN/NALWARN
Kenwood TM-733A, FT-50R
Sangean ATS909 w/wires
*** Un-key the mic to reply via e-mail ***
===========================================

Ref: Computer noise..

FWIW..I started this crusade back about 4 years ago to get
the noise out of my Icom radio.

The following is my track to a quieter system:

1. Got rid of the UPS system. It has a switching
power supply..they are cheap and radiate rf all
over the place. I moved to the Mandrake-Linux
OS..didn't really need the UPS..the OS has a file
system that takes care of itself on power failures
etc. It can recover after crashes.

2. When I got a new computer, I made sure that the
power supply was not the switching type and that
it was shielded and the latest FCC specs were
adheared to. Also, the newer cases have rfi
grounding and are shielded better.

3. Later changed to a quiet Router by Netgear.
The wall-wart bar power supplies on the wall
that was used a couple of years ago are also
the cheapo switching supplies that radiate
noise all over the house.

4. Went to a quiet DSL modem. The newer Zoom DSL modems
are state of the art..super quiet power supplies and
silent DA converters.

5. Fixed a noisy florescent light in the kitchen upstairs.
Noisy starter.

6. Went to a Flat panel monitor by Samsung. Much quieter
than my old regular 17inch CRT. This was one of the
main noise generators on my system.

This all over a 4-5 year period. Now I can listen to my
Icom receiver while browsing the net, the receiver is
within 4 foot of the Flat panel LCD monitor. Also, I
put in a RS 4 ft. ground rod just outside my window
for the Icom receiver.


Anyway, it can be done..but, it takes time and some
money.

Good Luck,

Leonard...
__________________________________________________ _______


On Sun, 14 Sep 2003 09:38:09 -0700, Tim Shoppa wrote:

I've got a few PC's in nice metal cases. I can actually run most of my
receivers near the PC without too much problem, as long as the receiver is
powered by batteries. But the instant I hook my sound card to the receiver,
or I run the receiver off of AC power, all the SW bands are filled with
S9 hash generated by the computer and network equipment.

What's the most economical and reasonable way to deal with this? Will
RFC's on the power, ground, and sound lines be good enough? Those snap-
together ferrite cores from Radio Shack help a little, but not
nearly enough. In a few weeks my computer-controlled TenTec
RX-320D arrives and I want everything to be in ship-shape by then.

The computer equipment isn't "just a computer". It's several PC's,
an Ethernet hub, a DSL router, a UPS, etc. By experimenting I've discovered
that the computers themselves aren't so bad... but the networking
stuff (a necessity, I'm afraid) is abysmal.

The situation is serious enough that I'm seriously looking into optical
fiber links... anyone have advice for a low-budget solution that way?
If I can put the RX-320D upstairs away from all the Computer stuff, and
run the audio and RS-232 over optical fiber, I'd be in heaven. While
I know where to start for RS-232 over fiber, I don't know anything
about the available audio-over-fiber options.

Tim.

H Johnson wrote in message . ..
If that does not work, and since Radio Shack stuff is normally
readilly available, they sell a Ground LP Isolator (270-0054) that
should do the trick or you can roll your own using their isolation
transformer (273-1374) which is $4.

The problem isn't ground-loop related; the problem is horrible with even
battery-powered receivers plugged into the sound card. Interference goes from
minor before I plug it in, to S9 hash all over the SW bands after I plug
it in.

I already tried isolation transformers. The capacitive coupling through
the isolation transformer (measured to be about 100pF) lets way too much
noise through... the net effect of the isolation transformer is a very
minor improvement. Better grounding on the receiver side would probably
help here, I'm going to drive a rod down just for the receiver soon.

Perhaps a grounded receiver + an isolation transformer will do the trick.

If that doesn't do it, it looks like fiber optics will be the solution.

Tim.

What about bypass caps from the audio line to ground. Try various values from
..001 to .1 mmfd. You can get a bunch cheap from Dan's Small Parts on the web.

I'd keep bypassing everything in sight.

jw
wb9uai
milwaukee

In article ,
(Tim Shoppa) wrote:

H Johnson wrote in message
. ..
If that does not work, and since Radio Shack stuff is normally
readilly available, they sell a Ground LP Isolator (270-0054) that
should do the trick or you can roll your own using their isolation
transformer (273-1374) which is $4.

The problem isn't ground-loop related; the problem is horrible with
even battery-powered receivers plugged into the sound card.
Interference goes from minor before I plug it in, to S9 hash all over
the SW bands after I plug it in.

I already tried isolation transformers. The capacitive coupling
through the isolation transformer (measured to be about 100pF) lets
way too much noise through... the net effect of the isolation
transformer is a very minor improvement. Better grounding on the
receiver side would probably help here, I'm going to drive a rod down
just for the receiver soon.

Perhaps a grounded receiver + an isolation transformer will do the
trick.

If that doesn't do it, it looks like fiber optics will be the
solution.


If you didn't try it use a choke on the ground lead with the isolation
transformer. The ground lead probably let the noise around the
transformer.

--
Telamon
Ventura, California

"Tim Shoppa" wrote in message
om...
snip

What's the most economical and reasonable way to deal with this? Will
RFC's on the power, ground, and sound lines be good enough? Those snap-
together ferrite cores from Radio Shack help a little, but not
nearly enough. In a few weeks my computer-controlled TenTec
RX-320D arrives and I want everything to be in ship-shape by then.

I own an RX-320. When I first hooked it up, I used a long wire antenna
which tended to be quite noisy. Was using an old (100mhz) computer with low
quality graphics. Built a folded dipole with (tv) coaxial input to radio.
Installed it in my roof. Everything became quiet.

I have since replaced my computer and monitor (high power, high quality
graphics, high refresh rates, etc.) and everything is still quiet. The
radio is less than 2 feet (as the mosquito flies) from the computer. I
still occasionally use the long wire to monitor the HF band edges and MW/LW
frequencies.

Information on the antenna can be found on Yahoo Rx-320 group
(groups.yahoo.com/rx320 message 2471, dated May 18, 2002.

(Tim Shoppa) wrote in message . com...
I've got a few PC's in nice metal cases. I can actually run most of my
receivers near the PC without too much problem, as long as the receiver is
powered by batteries. But the instant I hook my sound card to the receiver,
or I run the receiver off of AC power, all the SW bands are filled with
S9 hash generated by the computer and network equipment.

The RX-320 arrived Thursday, I hooked it up to the PC and got nothing
but hash all over the bands. Then I looked at the ground my AC house
wiring is hooked to (it's about a 40 foot run of wire from the AC
entrance panel to the cold water pipe! Maybe it was technically compliant
with the NEC when the house was built but it wasn't worth crap...) and
decided I had to be able to do better. So I went to Home Depot,
invested about $10 in some 1/2" copper pipe, and drove several 5-foot
lengths near a handy window.

Using this ground makes a world of difference. All the nasty noise
went away. I learned my lesson!

Tim.

Tim Shoppa wrote:

The RX-320 arrived Thursday, I hooked it up to the PC and got nothing
but hash all over the bands. Then I looked at the ground my AC house
wiring is hooked to (it's about a 40 foot run of wire from the AC
entrance panel to the cold water pipe! Maybe it was technically compliant
with the NEC when the house was built but it wasn't worth crap...) and
decided I had to be able to do better. So I went to Home Depot,
invested about $10 in some 1/2" copper pipe, and drove several 5-foot
lengths near a handy window.

Using this ground makes a world of difference. All the nasty noise
went away. I learned my lesson!

Tim.

Nice work. However it's not a good idea to have more than one ground
point for your domestic wiring. I suggest disconnecting the old copper
pipe ground wire near the circuit panel. You can leave the long wire in
place.


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On Sun, 28 Sep 2003 0:02:29 -0500, starman wrote
(in message ):

Tim Shoppa wrote:

The RX-320 arrived Thursday, I hooked it up to the PC and got nothing
but hash all over the bands. Then I looked at the ground my AC house
wiring is hooked to (it's about a 40 foot run of wire from the AC
entrance panel to the cold water pipe! Maybe it was technically compliant
with the NEC when the house was built but it wasn't worth crap...) and
decided I had to be able to do better. So I went to Home Depot,
invested about $10 in some 1/2" copper pipe, and drove several 5-foot
lengths near a handy window.

Using this ground makes a world of difference. All the nasty noise
went away. I learned my lesson!

Tim.

Nice work. However it's not a good idea to have more than one ground
point for your domestic wiring. I suggest disconnecting the old copper
pipe ground wire near the circuit panel. You can leave the long wire in
place.


Uh, well, uh, but - you do realize that you're suggesting ungrounding the
entire house, don't you?

By code - if he did that - he should replace every 3-conductor outlet with
two-conductor outlets because the ground (green) has been removed from the
system (illegal as it can be, of course).

He did exactly as he should have.

He maintained the electrical ground ("earth") and he created an "antenna"
ground (chassis).



Gray Shockley
-----------------------
DX-392 DX-398
RX-320 DX-399
CCradio w/RS Loop
Torus Tuner (3-13 MHz)
Select-A-Tenna
-----------------------
Vicksburg, MS US