[amsat-bb] Solar RFI?

Greg Stahlman kj6ko at innercite.com
Tue May 9 15:49:37 UTC 2017

Problem is, solar MFGR’s are exempt from Part-15, BUT, the operators are not!  At least that’s the way I read it.


100uV/M is a LOT!  Especially when trying to run weak signal stuff!   My neighbor’s is about 18db over night time noise floor!


I heard good things about “Micro Inverters” vs the more common “Optimizers”, which are basically a DC-DC converter on the back of the panel, and they were right!  I had a 7KW system put on my roof but demanded they use  Microinverters and I hear NOTHING!!   Very quiet!


The Optimizers are a HUGE nuisance from 80M through 6M and even on 2M.   


Regardless if they fall under the 100uV/M, the main rule of Part 15 states simply  “…must not cause harmful interference, even if it results in the improper operation of the interfering device.”




From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Robert Bruninga
Sent: Tuesday, May 09, 2017 7:30 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Solar RFI?


RFI from Solar?

With solar now cheaper than coal, solar is exploding in to neighborhoods
with favorable progressive policies.

But, they can produce lots of RFI with significant impact on Hams operating

With 16 kW of solar on my roof, I feel in a good position to be proactive
in documenting the overall impact of solar on HF operations.

We’ve seen QST articles on the very high RFI levels from solar systems that
use microinverters and optimizers located at every single panel on the roof
which are a nightmare to filter, while string inverters are easy to filter
at the one location on the ground.

My thoughts are to come up with a standard test that Hams near solar
installations can do to document any RFI.  Although none of us will have
standard calibrated antennas or receivers, we can at least make comparative
measurements to background noise levels.  Either with the array on and off
or between day and night at a fixed distance from the array.

I believe the part 15 limits for unintentional radiators is for 100 uV/m at
a distance of 30 meters (100 feet).  On a 1 meter portable antenna I
calculate that is equivalent to 36uV or within a dB of S9.  That’s a lot of
noise (if I did that right)…

And if it was a full size dipole say on 20m, then the allowable noise would
be 20 over S9 (again, if I did that right) Wow.

If anyone wants to submit measurements Ill collect them.

My suggestion is to take a portable HF rig (FT-817 or TH-F6 or TH-D74) and
an approximate 1m whip antenna and report at 100 feet from the array, the S
readings with the array on and with it off (or day vs night).

I welcome more expertise in this area.  Although this is not an AMSAT
issue, this is the only email group I’m on that might have people with
those easy portable HF radios.

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