[digitalradio] Re: RFI-Free PCs?
You mentioned Class B for industrial applications. Is the intent of Class B to hold down the amount of RFI coming out of the computer and bothering other things? Or is it more to prevent strong RFI in the environment from screwing up the computer? I guess for ham radio we are concerned with both - I get noise in the receiver generated by the computer (and all the other assorted electronics lying around) and also have had RF get into the computer and mess up the keyboard.
Re: [digitalradio] Re: RFI-Free PCs?
I remember it as just the opposite. The idea was to protect broadcast radio and television. Class B was for use in the home where it might interfere with a neighbour. Class A was for commercial use as it was expected to be further away from any homes. If a business interferes with itself, it has the means to correct it. Neighbours don't have that kind of technical knowledge or resources. On Wed, Mar 26, 2008 at 11:48 AM, W5XR [EMAIL PROTECTED] wrote: The Class B cert. for industrial environments is because it is expected that there may be many devices concentrated in a small area and they want to reduce the radiation from that concentrated area. Bob
Re: [digitalradio] Re: RFI-Free PCs?
Spurious emissions: Electronic equipment from computers to intentional transmitters can produce unwanted radio signals and are subject to FCC regulation. For digital devices including computers and peripherals, FCC Class B is the more stringent standard, applying to equipment marketed for use in the home, even if it could be used elsewhere. Home users are likely to be annoyed by interference to TV and radio reception. Class A is a looser standard for equipment intended only for business, industrial and commercial settings. - Original Message - From: Russell Hltn [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, March 26, 2008 7:50 PM Subject: Re: [digitalradio] Re: RFI-Free PCs? I remember it as just the opposite. The idea was to protect broadcast radio and television. Class B was for use in the home where it might interfere with a neighbour. Class A was for commercial use as it was expected to be further away from any homes. If a business interferes with itself, it has the means to correct it. Neighbours don't have that kind of technical knowledge or resources. On Wed, Mar 26, 2008 at 11:48 AM, W5XR [EMAIL PROTECTED] wrote: The Class B cert. for industrial environments is because it is expected that there may be many devices concentrated in a small area and they want to reduce the radiation from that concentrated area. Bob
[digitalradio] Re: RFI-Free PCs?
--- In digitalradio@yahoogroups.com, Tony [EMAIL PROTECTED] wrote: All, Need to replace the PC in the shack and would like to find something that's RFI-free out of the box. I've had terrible luck with desktop PC's, but the last two laptops (Toshiba) were very quiet. I'm leaning towards something in the small-PC catagory with an LCD monitor. Sound card and multiple USB ports are a must. Any suggestions would be greatly appreciated. Tony -K2MO I went through this and found 2 things that solved the problem I tied the station earth to the metal case of the desktop and changed refresh rate of the monitors, this where most of the birdies where coming from. Now I can run dual screens with Cat5 extender on Mouse Keyboard + screen to another room, had to wind the cat5 cable through 15 turns on an old ferrite from TV tube to quieten it down. Peter - VK6AAL
[digitalradio] Re: RFI-Free PCs?
--- In digitalradio@yahoogroups.com, Tony [EMAIL PROTECTED] wrote: SNIP! I'm leaning towards something in the small-PC catagory with an LCD monitor. Sound card and multiple USB ports are a must. Any suggestions would be greatly appreciated. Tony -K2MO Hi Tony; I'd second the suggestion on assembling your own. I'd get a full metal cased mini-ATX. None of that foolishness with plastic windows in the sides of the case. There are numerous great deals; many choices on MBs and CPUs. If you're not looking for big CPU power even a socket AM2 Sempron-based system would be very affordable. Then you can always upgrade the CPU in the future if you wish. Everyone has on-board sound now, but you can jumper it off and install a discrete card if you wish. And USB ports are numerous too. Not to mention the option of putting in a PCI USB card for some extras. good hunting Pete K5BCG
[digitalradio] Re: RFI-Free PCs?
I agree on building your own PC. I built one using a cheapie case and power supply and it was pretty quiet. So I ordered another case and power supply, same catalog number from the same supplier, and what came was a bit different. The power supply was the worst broad-band noise generator I have ever met, even when the computer was turned off. I've been told that Antec makes good power supplies and boxes. On the other problem, high noise on CB and 10 meters, I've found that a battery-operated portable shortwave receiver is a great tool. I had a lot of trouble at first with power line noise. The power company was cooperative but not very skilled in finding it. I could walk around with the battery receiver and find the noise hot spots and then they could find the faulty line hardware. I read somewhere that your house is a high noise zone, and if you get about 15 feet away things get much quieter. I haven't yet got around to trying that with the portable SW receiver. I'm told that even wall-wart power supplies these days generate RF noise. Touch lamps are known to be a bad source of noise. One of my friends says to turn off Everything in the house, unplug all the wall warts, and see what kind of noise you have, and then put things back on one-by-one.
[digitalradio] Re: RFI-Free PCs?
Tony, I had the same question at one time and found building the box myself was the best solution. Asking for something out-of-the-box might be like searching for the Holy Grail! I'm using a great CoolerMaster case*, which is double-walled and uses a metal mesh instead of plastic for the bay covers. The power supply uses shielded cables and has been the quietest RFI pc I've owned. For what it's worth, here's what's in the box I have. I don't know if this has contributed to low noise, but here it is: Intel motherboard (DQ35JO) Core 2 Duo 3.0 CPU ATI x1650 PCIE (512MB) 2 sticks of 1GB Corsair XMS2 (DDR2) 2 250GB Seagate Barracudas (RAID0) Plextor DVD-RW Memory card reader in the floppy slot (All this for less than a Dell, dude.) The board has on-board sound, but pretty decent, offering a S/N ratio of around 95 dB. Better than a SoundBlaster Live. Great for digital modes. Using an LCD monitor is also a great idea. I recommend taking an AM radio to your local LCD reseller and scan across the ones they have on display. I got funny looks when doing so, but it's a good opportunity to educate the salesperson! I found that CTL and Viewsonic have some quiet models. PLEASE let us know the make and model if you find a RF quiet one. It might save us some work later. I also added ferrites and toroids in the case to where ever I thought they should go, including all fans. Be sure to wrap a couple around the cables from the front USB audio jacks. These might not be necessary, but I didn't want to troubleshoot the RF later. My hand-held AM radio gets zero buzz from the tower, but wave it in front of a CRT (even one of my LCDs) and it lights up! *The case model is here: http://www.coolermaster.com/products/product.php?act=detailid=2908 Whichever enclosure you get, stay away from those silly Plexiglas-type clear side panels! I also have the system grounded and the rig and PC on the same power outlet. I have the rig right under the PC, with a tin plate to further shield it. An overall picture of my setup, including my favorite 'accessory' can be seen (for now) via the link below. Hope that helps some! 73. Frank K2NCC http://evokefrank.googlepages.com
