RFI Mitigation example

[JoeHam]

See pages 5-8 of this document for a real life example of RFI mitigation on a UPS:

https://www.nccc.cc/jug/2021/02jug2021.pdf

25dB reduction at 3.5 MHz is significant!

 

[K8MEJ]

Thanks, Joe. That's a good read!

 

[ko6kL]

I have also had some RFI from my backyard solar power setup and have some photo's to share.



above is scrap part from power supply , a AC line filter with 20amp rating working well on DC lines to panels. ( note: an extra connector will be added to ground this case.

.

testing of low cost mppt300 charge controller from powerworks.com works well with the lipo battery pack... except for RFI.

.

Above photos, Fairrite choke cores help remove common mode noise from the switching power modules in the charge controllers or inverters...
we don't need any extra radio static as this is the power source for my ham radios in the backyard.
More info on preventing RFI/EMI from or to solar power systems can be found in the QST archive.
here is a peek at it.

http://valleymedia.org/satchat/k1kp-416-34-35.JPG

 

[JoeHam]

Curious about the choice of mix 75 ferrites.

Good up to about 10 mHz. Don’t you operate on 20m and up?

Especially with the new sunspot cycle 10 and 12m were hopping recently.

 

[AntronX]

75 mix has very sharp absorption at 2 Mhz for small cores and 1 Mhz for larger cores with multi turn windings. Good for AM broadcast band filtering. But I found mix 31 to be more broadband, especially good from 0.5 - 5 Mhz with 10 - 20 turns.

 

[JoeHam]

Exactly.

Simple freq table here :

All Ferrite Ring Toroid Cores - Slip On Ferrite Beads - Palomar Engineers®

palomar-engineers.com

Actual response curves and more great information found elsewhere on Palomars website.

 

[ko6kL]

The type 75 cores are much lower cost around $1 ( vs 4-16$ ) and switching supplies ( pcm , mppt ) run at the 30-300kc or lower (0.3 mhz ) , so my thinking is that this is a good match. I know we often need more choking at HF and can add 31 or 43 if needed... If someone knows of better charge controllers , inverters etc i would love to hear what works for you??? At home I have a Sunnyboy 7.0 inverter system
its heavy so i guess is a low frequency inverter ?? ) with two strings of 300w panels all choked up with a 100amp broadband filter on the inverter output side on the 220VAC right from the install. not really any RFI problems on receive and i have not damaged it when I work 1.8mhz-1296mhz up to 400watts RF. when transmitting.

 

[Jerrys13]

See pages 5-8 of this document for a real life example of RFI mitigation on a UPS:

https://www.nccc.cc/jug/2021/02jug2021.pdf

25dB reduction at 3.5 MHz is significant!

Excellent article Joe! Thank you so much for providing it! I did notice that they said the power poles were rated at 75 amp but when you zoom into the phot of the Trip Lite it's 24V @ 40 amp. Maybe the photo was not the model that they used? And DANNNG that's a monster toroid! I plan on using 0AWG so turns will not work for me. And to think the K3 is only 100Watts! I'd like to do 3 Quadra's stacked which is the purpose of my 240V side. Thanks again for the real field experience article!

 

[Jerrys13]

I have also had some RFI from my backyard solar power setup and have some photo's to share.
View attachment 71446

View attachment 71447
above is scrap part from power supply , a AC line filter with 20amp rating working well on DC lines to panels. ( note: an extra connector will be added to ground this case.

.
View attachment 71448
testing of low cost mppt300 charge controller from powerworks.com works well with the lipo battery pack... except for RFI.

.
View attachment 71449
Above photos, Fairrite choke cores help remove common mode noise from the switching power modules in the charge controllers or inverters...
we don't need any extra radio static as this is the power source for my ham radios in the backyard.
More info on preventing RFI/EMI from or to solar power systems can be found in the QST archive.
here is a peek at it.

http://valleymedia.org/satchat/k1kp-416-34-35.JPG

Thank you for posing this Ko6! I'm sure everyone appreciates keeping their electronics quiet. I for one appreciate it!

 

[ko6kL]

I sent a email to our youtube friend encouraging him to add a tiny spectrum analyzer ( $60) to his tool box...
I want to know the spectrum output from anything Im going to add to the ham radio home.

the TineSA can be used like this...

 

[JoeHam]

I agree. The idea wasn’t as popular as the Nano VNA when I brought that idea to the forum but I wouldn’t be without either tool.

Tiny Spectrum Analyzer

When I brought up the Tiny VNA months ago some folks found it helpful. Here again is a product in the $50 range that won’t replace a multi kilobuck analyzer but it does a crazy good job. I ordered one from here April 29 and it should arrive this weekend...

diysolarforum.com

 

[ko6kL]

I wonder if one way to test a solar power system could be to put the antenna analyzer on the long leads going to the roof at night and see if it acts like a antenna at any frequency in the ham bands... perhaps need a DC blocking cap in the line to keep the PV from backfeeding the analyzer...
Im still getting a few blips on 10meters ( 28mhz ) around the back yard system.
looking for a metal box for my set up now , hopefully will contain the noise more.

 

[JoeHam]

I wonder if one way to test a solar power system could be to put the antenna analyzer on the long leads going to the roof at night and see if it acts like a antenna at any frequency in the ham bands...

I assume you would be looking for resonant frequencies but RFI doesn’t really need a resonant antenna to radiate.