[RFI] LED Street lights

[Jim Brown]

On 8/24/2023 3:13 PM, Hare, Ed, W1RFI via RFI wrote:
> I tend to agree, although Ethernet wiring, if properly installed, seems to be reasonably well balanced and does not radiate significantly... usually.

Structured cable consists of four very tightly twisted pairs, each 
having a different lay (the cable industry's name for the twist ratio) 
to minimize crosstalk between the pairs. The twist ratio is tight enough 
to minimize radiation at HF, but degrades with increasing frequency. 
Back in Chicago, I used CAT5 to run my landlines around (my XYL and I 
both ran our own biz at home). Before moving into that 120 year old 
house, I had a lot of steel conduit installed to run telco, Ethernet, 
audio, and RF around the house, in addition to power.

In addition, to radiation of the differential signal, there can be 
common mode leakage, depending on the quality of the output transformer 
or circuitry. Back in Chicago, 20 years ago, there was enough trash on 
2M to wipe out a suburban repeater on a talkie in my office near an 
ethernet cable. And, as Henry Ott reminded me back then, both ends of an 
Ethernet link are transmitters.

A year or so before I moved, I switched to Wi-Fi, and I use nothing but 
Wi-Fi here in the Santa Cruz Mountains.

Back in Chicago, I heard lots of Ethernet birdies on 30M and above. The 
clocks in every client sync to the hub/switch, and if you have five 
neighbors with Ethernet, you'll hear five birdies around each nominal 
frequency. On 20M CW, it's 14029-30, on 15, it's 21052, on 10 and 6, 
they're VERY near the bottom of the band.

Also around 2005, I also encountered massive RF trash from a POE feed to 
microwave dishes that had been installed at a decommissioned AT&T Long 
Lines site that WA6NMF bought, and where I built an HF station.

73, Jim K9YC