[Elecraft] OT: RF noise in solar photovoltaic system

[Howard Hoyt]

Alan,

I've worked with a large local PV installer to solve RFI problems, and I 
can vouch for the fact that it can be difficult to de-noise PV 
interters. the MPPT circuit is not analog and can turn the DC input 
lines into hash antennas, and as you stated, the inverter itself can put 
RFI on the 120/240 interconnect.

When I was in the market for PV equipment, I took a small battery 
operated emergency radio and visited several sites as well as showrooms 
of local vendors where they had demo systems.  The quietest PV install I 
found used the SMA 3000US inverter.  I just looked on-line, and the 
closest I could find to this model is now called the 3000TL 
(transformerless) so I cannot vouch for it's RFI characteristics.

I installed it using a combination of EMT and BX wiring to shield the 
input and output wiring, with twisted conductors in the conduit, adb BX 
having inherently twisted conductors.  I see zero increase in my noise 
level due to the PV system from my 160M OCF which goes right over the 
house, so I can definitely recommend that model SMA. They are not the 
cheapest inverters, but as a student of switching supply design, I know 
the least RFI-generating topologies are not the cheapest, and good 
transverse and common-mode filtering is not cheap to implement at the 
power levels a PV system can operate.

Contact me if you need any other info.

Howie - WA4PSC