[RFI] Trying to avoid Solar RFI

[James Gordon Beattie Jr]

Jim,
Thank you for taking the time to provide that summary.  I'll follow-up on your web site.  I've been there many times before, so with your summary in my frontal lobe, I'll dig in.

The pigtails on each panel use MC4 connectors and I am assuming that the wires that are provided are untwisted.  They will get chokes.

I was planning to use #12 or #10 red and black power wires and twist them with a drill chuck unless there is a suitable cable product.  At 48 VDC, I should be able to connect all the panels and then unify them with something heavier to go to the shed.

I'll also bury the DC to the shed and the AC to the well and to the ham shack.

As for the inverter, I will take measurements on the starting current of the well and go from there.

Many thanks!


73,
J. Gordon "Gordie" Beattie, Jr., W2TTT
201.314.6964
W2TTT at ATT.NET
Gordon.BeattieJr at VIAVISolutions.com


Get On The Air!

________________________________
From: RFI <rfi-bounces+w2ttt=att.net at contesting.com> on behalf of Jim Brown <jim at audiosystemsgroup.com>
Sent: Friday, December 16, 2022 4:19:47 PM
To: rfi at contesting.com <rfi at contesting.com>
Subject: Re: [RFI] Trying to avoid Solar RFI

On 12/16/2022 12:45 PM, James Gordon Beattie Jr wrote:

> Thoughts?

Several. Because charge current regulators control the width of a train
of square waves, it's critical that all DC wiring be twisted pair, with
no interruptions of the twisting where panels and batteries are
connected. That DC circuit is 100% modulated by that wave train, so it
must be viewed as RF, not DC. Just as Elecraft shapes its CW keying to
optimize readability while minimizing clicks, charging waveforms must be
optimized for efficiency and to minimize RF noise. N6KR describes what
he's doing as a "sigmoidal" or raised cosine shape. Wayne first did that
for the K3; Flex subsequently adopted it after ARRL tests of their 6500
series rigs showed rather wide clicks.

  You're right to run the system at the highest practical voltage, which
proportionally reduces the current. RF noise is proportional to the
square of current. It's also good practice to insert effective common
mode chokes in that wiring. The winding guidelines for parallel wire
transmitting chokes are a good starting point. The second link for
VHF/UHF coax chokes can be used as a starting point for parallel wire
chokes.

http://k9yc.com/2018Cookbook.pdf
http://k9yc.com/ChokesVHF.pdf

Proper bonding of everything on the AC side is critical, and twisted
pair should be used for the current-carrying conductors as well.

With respect to the well -- starting current for the motor is probably
the most demanding spec. My 6kVA Honda inverter generator won't run
mine, which is on a 100 ft well.

I've seen a few reports that Tesla battery systems are RF quiet. My
Model 3 is quiet both driving and charging at home -- I have VHF/UHF
running in mine, and I've seen reports from others that HF is relatively
quiet as well. Unfortunately it doesn't run in the family -- electronics
for my Starlink system required extensive choking to cool off.

73, Jim K9YC

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