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Re: [RFI] SolarEdge Resolution

To: rfi@contesting.com
Subject: Re: [RFI] SolarEdge Resolution
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 23 Jan 2020 15:21:58 -0800
List-post: <mailto:rfi@contesting.com>
Thanks Gary.

FWIW, Fair-Rite #75 is not a great material for HF, but it's useful for 160M and down.

73, Jim K9YC

On 1/23/2020 2:44 PM, Gary Johnson wrote:
TJ Simpson from SolarEdge was here with a crew that did their final phase of 
noise mitigation on the 6 kW system next door. Several months ago, they had 
re-routed all cabling to reduce loop areas and installed common-mode chokes 
(type 31, probably not enough turns) on the outputs of all Panel Optimizers. 
That produced no change in the interference I noted which consisted primarily 
of 200 kHz-spaced S7 noisy carriers present on most HF bands. My reference 
antenna for all measurements is a low fan dipole that is about 30 feet from the 
nearest solar panel.

This upgrade involved replacement of all Panel Optimizers with their newest 
model SP350-5NM4MRM-MM25 which uses spread-spectrum communications rather than 
the previous fixed-carrier technique. It also contains type 75 ferrite 
common-mode chokes on the output conductors. The central inverter was also 
replaced (model SE7600-A). This 8.3 kW inverter has an FCC Part 15 statement on 
it. A close approach to the inverter with my DFing loop and shortwave radio 
told me that this is what I would classify as a quiet system. I would not 
expect the inverter itself to cause significant interference, based on personal 
experience investigating a great many RFI-producing devices.

The 200 kHz-spaced carriers are gone as expected. Instead, there are now a 
large number of low-level signals particularly across the 20m band. They sound 
much like the old carriers though much weaker. The typical spacing varies 
widely from 3-20 kHz. The strongest ones are 10-15 dB above the noise floor. 
Those new signals are very weak on 15m an above. I did not see them on 40m. I 
would say 20m is the band that takes the biggest hit.

There were only a few minutes for me to get any baseline data with the entire 
solar system completely disconnected because I didn't know the work was planned 
for that day. What I did determine is that my wideband noise floor across the 
20m band is about 6 dB higher when the upgraded system is turned on. Baseline 
noise has no particular sonic character; it simply sounds like white noise. So 
the energy is in fact spread, albeit with those numerous small signals. Below 
14 MHz, RFI from LED lights next door plus other sources completely dominates 
at my location during the evening hours. Therefore I cannot comment much on 
lower-frequency RFI from the SolarEdge equipment.

My conclusions are:  1. When properly installed, the latest generation of 
SolarEdge Panel Optimizers can be compatible with HF radio if your antennas are 
not too close, obviously dependent upon how quiet your QTH is to start with.  
2. The company did respond to my complaint (submitted by my neighbor), and did 
the work in good faith and at no cost. 3. TJ Simpson is in my opinion a 
reasonable and knowledgeable fellow and I'm lucky to have a human being to talk 
to at an otherwise huge, faceless corporation.

Overall, my very humble home station is really no worse off than it was before 
this solar equipment was installed, since there are so many other sources of 
RFI bombarding me. Thank heavens I now have a nice, permanent, remote station.

73,
Gary NA6O @W6SRR

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