Topband: Tesla Powerwall and RFI

[Jim Brown]

On 5/18/2020 3:15 PM, Paul F. Merrill wrote:
> Hi Group -
> 
> Does anyone have any experience with a Tesla Powerwall installation at
> their QTH?  If you have, have you noticed any RFI from them?

Someone posted a link to this ham's blog, but now I can't find the post.

http://ka7oei.blogspot.com/2017/12/does-tesla-powerwall-2-produce-rfi.html

http://ka7oei.blogspot.com/2018/10/reducing-rfi-from-tesla-powerall-2.html

Anyhow, I went there and browsed it. There's a lot of good information 
there, but the author doesn't seem to understand the concept of 
saturation in the clamp-on ferrite parts that he places on individual 
conductors, nor the concept of a common mode choke applied to all three 
conductors, which eliminates saturation.

He observes that you've got to have an antenna right next to Powerwall 
wiring to hear it on any band above 160M, and it still isn't bad there, 
but that it gets increasingly problematic as you go down in frequency, 
and is pretty bad by the bottom of the AM broadcast band.

The problem he faces is that he needs a pretty large i.d. clamp to 
surround the three conductors (phase, phase, neutral), and #75 is the 
material he's chosen to work with. The largest clamp-on has a 
dimensional resonance around 750 kHz

https://www.fair-rite.com/product/round-cable-snap-its-475176451/

A possible solution would be to wind a suitable three-wire choke on one 
or more 2.4-in o.d. #75 toroids using a wire diameter sufficient to 
carry the current. In http://k9yc.com/630MTXChokes.pdf  I showed the Z 
plot for 18 turns of RG400, which provides about 2.5K on 630M and 160M. 
Dimensional resonance is too high for #75 to be useful much below 300 
kHz. Although I didn't publish measured data for a #12 Teflon pair, my 
recommendation for 630M was 17 turns.

Another observation. Santa Claus brought us a Model 3 (delivered a bit 
late on the afternoon of New Years Eve), and I sometimes charge it at 
home on a 20A 120V circuit. It's slow, but it works, AND I hear nothing 
from it on 160M when I probe along the short run of #10NM that feeds it. 
It is also my understanding that the increasing noise in the AM band is 
the reason there's no AM radio in Teslas. AND another observation -- the 
interior of that vehicle is very carefully shielded at some frequencies 
but not at others. My VHF/UHF talkie is useless inside the vehicle, 
suggesting that the glass is providing shielding. BUT -- my cell phone 
works fine inside, so that shielding is carefully tailored to couple 
cell frequencies.

And finally, the FM radio with it's antenna(s) in the Model 3 has 
excellent sensitivity. All of the stations I listen to are NPR stations, 
and I'm not in the service contour of any of them, so I really notice 
weak signal performance. The radio in my XYL's Prius is often hunting 
between digital and analog streams; not the Tesla -- it nearly always 
holds the digital streams as I drive up and down the mountain from home 
into town(s).

Note also his observations with respect to the solar part of the system, 
which I believe to be good advice. W6GJB has been doing some research of 
his own in preparation to building his own custom installation with off 
the shelf components.

73, Jim K9YC