Posted by Karl on Aug 17, 2019; 11:14pm
URL: https://www.es-forum.com/where-to-go-any-ideas-tp4034304p4034312.html

Casper, this is what they say in their spec-sheet:

EMI/RFI Noise Attenuation:    30dB Max. from 1kHz to 10MHz
Capacitance:Up to 3.5 uF Max.

I think that some Belkiin power strips claim >30 dB, but when I tested them they made no difference in noise on the AM radio.

My gut feeling is that $1,200 is too much. If they have a no-questions-asked return policy, you could try it and let all of us know :)

You have a lot of options at that price point. For example, you could buy four isolation transformers:

http://www.antekinc.com/an-154115-1500va-115v-transformer/

...and put them inside a 12" diameter, 1/4" thick steel pipe connected to a 6' deep grounding rod. That would give you 50 amps of capacity, which I think is enough to satisfy the building codes in most places. If your building code has a 20 amp minimum for each circuit, you could connect all of the 'dirty' appliances to one pair of transformers and all of the sensitive things (like bedroom lights) to the other pair (which would help to keep them separate).

The catch is that some types of noise will go right through an isolation transformer.  The easiest and cheapest way to test whether it will work for you (before spending the money) would require you to violate code, so an electrician probably won't do it for you. (Most of the time you won't use anywhere near 50 amps. So you could wire a much smaller and cheaper transformer in between your meter and your main breaker box - WITH AN APPROPRIATE FUSE - and test it with an AM radio, or just see if you felt better.)

You can also build a lot of smaller filters for less than $100. The parts are not too expensive: https://www.digikey.com/product-detail/en/illinois-capacitor/105MMR250K/1572-1190-ND/5410542

Here is an article by a different manufacturer about the problems with off-the-shelf filters: https://docs.wixstatic.com/ugd/53be97_320fa114167346d2afe453637487e292.pdf

(I'm not endorsing their products and I haven't used them.)

From the article: "The absolute majority of EMI filters on the market are designed to meet EMC regulations. Equipment designers are encouraged  to  select  the  lowest-cost  filter  that  attenuates  EMI  just  enough  to  pass  EMC requirements in  the laboratory–anything  more  than  that  would  be a waste  of  money  since  in  the EMC laboratory  environment  a better filter won't improve the product's performance or add to product's value."

Also from the article:



I've had much better luck filtering DC power: https://youtu.be/d8YSXtMFEe4

(I wasn't feeling well when I made that video, so I originally didn't post it, but it seems relevant here.)