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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