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Computer+receiver=noise. How to filter?
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. |
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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 |
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"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. |
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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. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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 |
Gray Shockley wrote:
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 I said he shouldn't have more than one ground point for his domestic wiring. I was under the impression that he made a shorter grounding system to the main panel from some new ground rods outside a near by window. If the circuit breaker panel is grounded with his new rods, he doesn't need to keep the old 40-ft ground wire to the copper pipe. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Here's a good link on grounding. The primary focus is lightning, but it's
still good: http://www.polyphaser.com/ppc_PEN1016.asp "Tim Shoppa" wrote in message om... (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. |
Gray Shockley wrote in message ...
He maintained the electrical ground ("earth") and he created an "antenna" ground (chassis). Yeah, that's what I did, and it worked very nicely. But it's also clear that the ground at the AC entrance panel isn't doing so well itself. I've got to find the relevant section of the NEC and figure out how I can both comply with the code *and* put a ground there. I'm 100% sure that what I did (5 foot copper pipes) for the radio ground isn't compliant for the AC entrance ground. Tim. |
Tim Shoppa wrote:
Gray Shockley wrote in message ... He maintained the electrical ground ("earth") and he created an "antenna" ground (chassis). Yeah, that's what I did, and it worked very nicely. But it's also clear that the ground at the AC entrance panel isn't doing so well itself. I've got to find the relevant section of the NEC and figure out how I can both comply with the code *and* put a ground there. I'm 100% sure that what I did (5 foot copper pipes) for the radio ground isn't compliant for the AC entrance ground. Tim. Thanks for clearing that up. After posting my first reply I realized your new ground rods might only be for the radio. I thought they were for the AC entrance and domestic wiring. That's why I said you didn't need two ground systems for the house and could disconnect the old one. If you try another method for grounding the AC entrance, try using the radio without it's new ground rod system and let us know if the noise gets worse or stays the same. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
If you drive two ground stakes in about 20 feet apart and measure the
_AC_ voltage between them, it's typically about a half volt. It's thousands if lightning hits nearby. (The ambient voltage comes from stray power line ground differences. The earth levels them out as best it can but it prefers your electronics when available.) So you don't want your radio to be part of the path between two grounds in thunderstorms. Disconnectect from the radio ground when you disconnect from the antenna, is one approach. -- Ron Hardin On the internet, nobody knows you're a jerk. |
All ground rods have to be connected together to comply with the NEC.
"Ron Hardin" wrote in message ... If you drive two ground stakes in about 20 feet apart and measure the _AC_ voltage between them, it's typically about a half volt. It's thousands if lightning hits nearby. (The ambient voltage comes from stray power line ground differences. The earth levels them out as best it can but it prefers your electronics when available.) So you don't want your radio to be part of the path between two grounds in thunderstorms. Disconnectect from the radio ground when you disconnect from the antenna, is one approach. -- Ron Hardin On the internet, nobody knows you're a jerk. |
Leave the existing AC panel ground alone! Make sure that you tie your new
ground to the existing power panel ground. Failure to do that can result in unnecessary damage in the event of a nearby lightning strike because the two separate grounds could be at vastly different potentials. The damage could be to your equipment or home. I'm sure your homeowner's insurance company would not look kindly at your having removed the power panel ground, resulting in damage to your home. "Tim Shoppa" wrote in message om... Gray Shockley wrote in message ... He maintained the electrical ground ("earth") and he created an "antenna" ground (chassis). Yeah, that's what I did, and it worked very nicely. But it's also clear that the ground at the AC entrance panel isn't doing so well itself. I've got to find the relevant section of the NEC and figure out how I can both comply with the code *and* put a ground there. I'm 100% sure that what I did (5 foot copper pipes) for the radio ground isn't compliant for the AC entrance ground. Tim. |
"CW" wrote in message .net...
All ground rods have to be connected together to comply with the NEC. Not only that, but at least the version that's applicable to my locality says that: 1. The point at which they are connected together must be the AC entrance panel. They absolutely must never be connected together over the inside- to-the-house ground wiring (and I think I understand why... you do not want your house wiring to be carrying a couple thousand amps in case of a nearby lightning strike). 2. The cold water pipe must also be connected to the AC entrance panel. I'm a little less clear on why that must be, but it doesn't seem to hurt anything. There's a whole litany of what type of ground rod must be used and what gauge of wire too... I've got more reading to do. I think (but I'm not sure) that the copper pipes I sank for my experiment are not good enough for a code-compliant ground because they are both too short (5 feet is too short) and not copper plated steel. The experiment was still worthwhile in that it showed how bad the 30-year-old house ground was. There are some additional rules if a tower is involved but I don't have a tower so I didn't pay any attention to them. Tim. |
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