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Author Topic: Ethernet over house wire powerline  (Read 2574 times)
WA2ISE
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Posts: 1205




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« on: May 03, 2018, 01:05:39 PM »

Picked up a pair of NETGEAR ethernet over house wire adapters at a garage sale mainly for grins, and to see how much RFI they'd cause.  They operate in the HF spectrum.  Goodbye HF ham radio?

on non-ham HF bands I can hear pulses running around 50 to 100Hz from these.  But they appear quiet on ham bands.  According to their web page https://kb.netgear.com/22054/XAV1601-FAQs:

"What type of modulation does Powerline use?
OFDM (Orthogonal frequency-division multiplexing).

Does Powerline interfere with HAM Radio signals?
By using OFDM (orthogonal frequency division multiplexing), we create different interleaved channels or carrier frequencies (up to 1155) that can be transmitted on.
We also turn off these specific frequencies (according to each country regulations) to make sure they don't interfere with other RF signals – like Amateur Ham Radio operators.
Indeed, notching out those frequencies from use (effectively using only 917 of the 1155 possible frequencies from 2 to 30 MHz) reduces overall throughput, but ensures that we don't impact HAM Radio communications."

Looks like either one or more of the engineers at Netgear was a ham, or they knew from elsewhere that we'd squawk loudly to the FCC if their devices trashed our bands.   Cheesy
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K0BT
Member

Posts: 14




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« Reply #1 on: May 03, 2018, 01:40:29 PM »

I used these for years without any detectable interference.  They actually worked very well.
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NK7Z
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Posts: 2334


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« Reply #2 on: May 03, 2018, 03:37:45 PM »

The early ones were QRM makers, the later ones, had filters in them for the Amateur frequencies.  See:

https://www.nk7z.net/rfi-snapshots/

then select "Computing device RFI", and you will find a SDR snapshot of the RFI generated by the devices...
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
W1VT
Member

Posts: 2787




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« Reply #3 on: May 04, 2018, 07:43:22 AM »

http://www.arrl.org/files/file/bpl/HomePlug_ARRL_Dec_2000.pdf
There was a joint test between the ARRL and Homeplug that led to the notching of signals to reduce interference in the amateur bands.
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KOP
Member

Posts: 330




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« Reply #4 on: May 18, 2018, 07:23:33 AM »

I had sent Ron, KA7U , a screenshot of his web sdr that showed a series of nasty spurs @ 7.282MHz . Initially because they occurred locally as well as at several other stations I thought it was a regional thing. Come to find out it's more of a ubiquitous thing. If the interference is anything like "As you go up in frequency to 18MHz and beyond these spurs repeat on 60KHz intervals and peak around 18-20MHz." then suspect a router , switch, or CatV within the house. I've used the capacitively connected to ground conduit method here and saw some improvement but still have a ways to go :-/

The first image from your attachments is a spur from my home Ethernet network. I've worked to reduce those but have not done a complete job. At the time you took the screen shot the interfering spurs are at -102dB and provide an obnoxious ring. As you go up in frequency to 18MHz and beyond these spurs repeat on 60KHz intervals and peak around 18-20MHz. The active loop antenna on the 8074 port displays them at greater amplitude than the 210' dipole. The dipole is fed with coax via an underground conduit and is 380' west of the receiver. From where that coax enters the radio shack it is in a steel conduit to the 2nd floor radio shack. So that coax shield is capacity coupled to ground and effectively shielded over most of the run which effectively removes local mode noise such as the Network routers, switches, power supplies, TV sets, flouresent lights, pump motors, etc. The active loop antennas have exposed coax laying on the ground for 100' west of the radio shack but the KiwiSDR is Network connected and sits beside a network switch. The local mode chokes on the power supply and coax reduced the network spurs on average -5dB and using shielded network cable along with a shielded netowork switch at this location reduced them on average another -5dB. So I improved the local mode noise but have not completely eliminated it. I'm currently experimenting with a twisted pair feedline (CAT5e) for the LNA at the loop antenna and it is reducing the network spurs even more, but my prototype LNA for this feed system needs different transistors to work properly and I'm waiting on those. If you are curious about this LNA and feed system, you can check it out here:  https://easyeda.com/doxnairobi/

Again many thanks to Ron, KA7U for sharing



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I considered a microwave oven magnetron and a 4' dish as a drone-killer. The ERP would be on the order of a hundred thousand watts or so. ~anon
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