[RFI] Enphase Solar System RFI Tests

[K9MA]

My next door neighbors recently installed a solar system, with the 
panels no more than 60 feet (18 m) from my antennas. The primary antenna 
is a tribander at 70 feet, with a 40 meter rotatable dipole 6 feet above 
it. I'm in an urban area, surrounded by overhead power lines, so the 
noise level is fairly high. At best it's about -130 dBm/Hz on 20 meters. 
So far, I have been able to detect no RFI from the solar system from 1.8 
to 28 MHz. Details below.

The solar system consists of 14 320W panels, each with an Enphase IQ7+ 
microinverter. It is a grid-tied only system, with no batteries or 
standalone operation.

At my request, ferrite snap-on split cores were installed. Each short DC 
lead from panel to inverter had two Fair-Rite 0431178281 cores attached 
near the inverter. On the AC cables, Fair-Rite 04311164181 cores were 
used. On 9 of the inverters, one core was attached the the input lead 
and one to the output. On the remaining 5 inverters, a core was attached 
only to the output lead. (Two, at the ends of the chains, had no input 
connection, and I ran out of cores for the other 3.) One additional core 
was attached to each AC cable to the junction box, about 5 feet from the 
closest inverter.

I checked out a couple other Enphase systems in the area with a small 20 
meter loop and preamp. No RFI was detected but, of course, the small 
antenna is not very sensitive.

There is no way to know from this data whether all the ferrite cores 
were necessary. Even if they were, however, it shows that fairly simple 
and inexpensive mitigation measures are adequate with this Enphase 
system, at least in an urban noise environment.

Both the neighbors and contractor were very cooperative. I paid for the 
$300 worth of ferrites, in the interest of maintaining good relations, 
but I shouldn't have had to do that. If the contractor had had to remove 
all the panels to attach the cores after the panels had been installed, 
it would have cost them much more than that. If I were to install my own 
Enphase system, or if another close neighbor were to, I would insist the 
installer pay for the ferrites and install them initially, or agree to 
retrofit them later if necessary. I would, however, waive my customary 
enormous consulting fee.

73,

Scott K9MA

-- 
Scott  K9MA

k9ma at sdellington.us