apache-labs.com

For the last day or so, I've been trying to trace a bizarre noise problem that occurs when the 8000DLE is operating. I am using an Icom 7300 and ANAN 200D for the noise display measurements.

I finally localized the source to a Netgear Gigabit Ethernet switch. If the 8000DLE is plugged into Port 4 of the Netgear switch, I see the noise as shown. If I move it to any other Neatgear port, the noise drops to zero.

So, a question for networking experts: why would one Netgear Ethernet port show this problem? A defective Neatgear product? I have to dig up another unit and swap it out. I'll report the result here.

Not sure this is the right forum for this posting, but it's the only one I see at the moment for 8000DLE questions. Moderators, please move if necessary.

Paul, W9AC

Okay, I swapped out the Netgear switch with an identical GS108 model and all is well. I guess something is defective with port 4 of the other Netgear switch. Interesting problem that lead me on quite a chase. I did not initially suspect the Netgear device to produce switching noise at regular intervals, especially since it's being fed from a linear power supply.

Paul, W9AC

Glad you found it, Paul! I was just going to post a whole bunch of stuff that was aimed at isolating it to the switch, not the radio, but you beat me to it!

73!

Scott

I'd think a bad ground on the one port.

A bad ground point could be the culprit. The root source of the GS108 noise is likely a DC-DC switching converter. I had an RFI problem a while back from a Netgear home router that used a switching converter. My first attempt to quiet it down was through the use of a +12V linear supply feeding the router's DC power input. That by itself did nothing to quiet the RFI.

Then, after pulling the router apart I spotted a switching converter. It was replaced with a high-current linear supply and that finally solved the problem. Enough switching noise was being coupled onto the power cable and CAT6 cabling to be picked up by my outdoor wire antennas. Choking the router lines helped some but that resulted in a ridiculous number of #31 ferrite cores hanging off the router.

Paul, W9AC

w9mdb wrote:I'd think a bad ground on the one port.

Exactly. Also, always use CAT 6 or better cables as they have good shielding.

Cat6 cables are nominally un-shielded twisted pair (UTP) cables, the same as Cat5 and Cat5E. All variants, Cat5, 5E or 6, will not have shielding unless you specifically buy shielded versions. Note that there is very little physical difference between Cat5 and 6: slightly larger conductor diameter, a faster twist rate, and a slightly larger overall diameter (increased spacing between conductors).

Be aware that if you are purchasing cables that are purported to be shielded but the connectors are not shielded then either a) the cable is not shielded and you've been ripped off or b) the cable is shielded but since the shield is not bonded to the equipment on each end via the shielded connectors then it has significantly less utility and you've been ripped off

If you are making your own shielded cables using Cat6 (or 5 or 5E) shielded twisted pair (STP) cable, do be sure to obtain the correct shielded RJ45 connectors and the correct tooling to terminate them.

73,

Scott