Re: Topband: Help with RFI
Jim's suggestion worked beautifully here! 14 turns of CAT5 cable on a single 2.4" #31 core works much better than the old choke with 5 or 6 turns through four stacked 2.4" #31 cores. It eliminated the last traces of RFI coming through my computer speakers running 700w on 75 meters. And three more turns of the line cord through the same core all but eliminated it on 40 meters. (If you haven't figured it out already, the dipole is much too close to the house.) 73, Mike www.w0btu.com On Sun, Jan 13, 2013 at 10:34 AM, Jim Brown wrote: > On 1/12/2013 7:38 PM, Mike Waters wrote: > >> I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my >> shack PC around a few stacked 2.4" diameter #31 ferrite cores. >> > > For 160M, 14 turns on a single #31 core is a pretty good choke. Don't > overlook power supply cables as a possible receiving or radiating antenna > for RF. A #43 core "works" at these frequencies, but not nearly as well. > > 73, Jim K9YC > _ > Topband Reflector > _ Topband Reflector
Re: Topband: Help with RFI
I'm reposting this to the reflector: Yes, I do have DSL. I have a very good RFI filter on the DSL line coming to the modem so I think it might be a cabling problem. Everything was working FB until recently when I reconfigured the hardware. I have a few clamshell filters and I also have some shielded cables so Monday I will do some substitutions and see if it helps. The problem is not across the entire band. It's only below 1825. Frequencies above 1825 don't bother me. This is probably 160 meter RF triggering the modem. Common mode chokes and shield normally will not do the trick, because the problem is differential. First, you need an immune modem. The best modem I found was a 2wire ADSL modem. Second, filters are almost impossible to buy. Because of that, I built my own filter. I added peaking at the high end of DSL, which for ADSL ends in the upper middle AM broadcast band area. http://www.w8ji.com/adsl_filter.htm 73 Tom _ Topband Reflector
Re: Topband: Help with RFI
On 1/13/2013 5:08 AM, Brian Machesney wrote: Wrapping everything in ferrite did not solve my 160m RFI problems. OZ7C provided a filter circuit that I use successfully: Let's define the problem. Interference to DSL is VERY different from interference to Ethernet. I agree with Pete that using wireless Ethernet for as much as practical of a system is a good thing, and I've been doing that since moving to CA seven years ago. My internet is CATV, so I've not had to tackle DSL myself. The problem with interference to DSL is that 160M is within the heart of the range of DSL signals, and both the equipment and the wiring are poorly designed to reject them. In the old days, all telco wiring was twisted pair, but in the last few decades it has been mostly downgraded to parallel conductors, and this has had a huge impact on RFI, noise, and crosstalk in difficult situations. There is also the issue of equipment poorly designed to reject the interference, or to switch to a lower bandwidth mode when interference is present. The issue of RFI to DSL has been worked through in considerable detail on the RFI email reflector, and the consensus is to first challenge the DSL vendor to fix it. A low pass filter for the telco line is also a good move, and so are replacing as much as practical of telco wiring with good twisted pair, like CAT5/6/7, and adding a serious common mode choke to the cables going to the modem. 73, Jim K9YC _ Topband Reflector
Re: Topband: Help with RFI
Im running shielded CAT 5e from the router up in the office to the basement and none of the rigs bothered it but I did have to use a single 31 core at the router outputs to eliminate its noise; the 6 CAT5e cables are grouped together thru the toroid, and another at the DC input. The cable modem that feeds it was also very noisy and even outputting on the RG6. Carl KM1H - Original Message - From: "Mike Waters" To: "topband" Sent: Saturday, January 12, 2013 10:38 PM Subject: Re: Topband: Help with RFI I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my shack PC around a few stacked 2.4" diameter #31 ferrite cores. Works for me. 73, Mike www.w0btu.com On Sat, Jan 12, 2013 at 4:48 PM, W7KW wrote: I am having a problem with RF getting into my Ethernet cables. Anyone have any recommendations for a clamp-on filter that would help remove 1.8 MHz RF? _ Topband Reflector - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2638/5530 - Release Date: 01/13/13 _ Topband Reflector
Re: Topband: Help with RFI
On 1/12/2013 7:38 PM, Mike Waters wrote: I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my shack PC around a few stacked 2.4" diameter #31 ferrite cores. For 160M, 14 turns on a single #31 core is a pretty good choke. Don't overlook power supply cables as a possible receiving or radiating antenna for RF. A #43 core "works" at these frequencies, but not nearly as well. 73, Jim K9YC _ Topband Reflector
Re: Topband: Help with RFI
I would also try shielded CAT-6 cable. It has more turns/foot than CAT-5 and is more immune to EMI, and supports faster speeds. -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Waters Sent: Saturday, January 12, 2013 10:39 PM To: topband Subject: Re: Topband: Help with RFI I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my shack PC around a few stacked 2.4" diameter #31 ferrite cores. Works for me. 73, Mike www.w0btu.com On Sat, Jan 12, 2013 at 4:48 PM, W7KW wrote: > > I am having a problem with RF getting into my Ethernet cables. Anyone > have any recommendations for a clamp-on filter that would help remove > 1.8 MHz RF? > _ Topband Reflector _ Topband Reflector
Re: Topband: Help with RFI
Wrapping everything in ferrite did not solve my 160m RFI problems. OZ7C provided a filter circuit that I use successfully: http://www.ddxg.dk/oz7c/adsl/adsl_160m_filter.pdf G3VMW has done additional work: http://www.rsars.org.uk/ELIBRARY/BBCONNECT.pdf 73 -- Brian K1LI On Sat, Jan 12, 2013 at 10:38 PM, Mike Waters wrote: > I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my > shack PC around a few stacked 2.4" diameter #31 ferrite cores. Works for > me. > > 73, Mike > www.w0btu.com > > On Sat, Jan 12, 2013 at 4:48 PM, W7KW wrote: > > > > > I am having a problem with RF getting into my Ethernet cables. Anyone > > have any recommendations for a clamp-on filter that would help remove 1.8 > > MHz RF? > > > _ > Topband Reflector > _ Topband Reflector
Re: Topband: Help with RFI
I would seriously consider going wireless. A few years ago I had a direct strike on the top of my tower. Fortunately, everything was disconnected, so I sustained no damage in the shack. In fact, the only significant damage was to two computers on a cabled Ethernet network, both of which showed physical signs of damage at and near the Ethernet port. It was clear to me that induced current from the strike, picked up by the Ethernet cable, was responsible. I switched our house over to wireless networking and have been completely satisfied. It doesn't hurt that it all operates at UHF. 73, Pete N4ZR Check out the Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com. For spots, please go to your favorite ARC V6 or VE7CC DX cluster node. On 1/12/2013 10:38 PM, Mike Waters wrote: I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my shack PC around a few stacked 2.4" diameter #31 ferrite cores. Works for me. 73, Mike www.w0btu.com On Sat, Jan 12, 2013 at 4:48 PM, W7KW wrote: I am having a problem with RF getting into my Ethernet cables. Anyone have any recommendations for a clamp-on filter that would help remove 1.8 MHz RF? _ Topband Reflector _ Topband Reflector
Re: Topband: Help with RFI
I wrap a few turns of the CAT 5 Ethernet cable coming into the back of my shack PC around a few stacked 2.4" diameter #31 ferrite cores. Works for me. 73, Mike www.w0btu.com On Sat, Jan 12, 2013 at 4:48 PM, W7KW wrote: > > I am having a problem with RF getting into my Ethernet cables. Anyone > have any recommendations for a clamp-on filter that would help remove 1.8 > MHz RF? > _ Topband Reflector
