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Re: [RFI] Galaxy Grow Light Ballast Update

To: rfi@contesting.com
Subject: Re: [RFI] Galaxy Grow Light Ballast Update
From: Tom Thompson <w0ivj@tomthompson.com>
Date: Mon, 1 Feb 2016 10:46:28 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Hi Jim,

My experience has been similar to yours. When I was developing my ballast filter, I not only found that the filtering was more effective on the lamp side, but I could gain another 10 dB by not passing the green wire on the lamp side through the common mode choke but winding a separate choke for the green wire. see:

http://tomthompson.com/radio/GrowLight/Ballast%20Filter%20Layout.jpg

Tom   W0IVJ

On 2/1/2016 10:38 AM, Jim Brown wrote:
On Mon,2/1/2016 9:08 AM, Hare, Ed W1RFI wrote:
I have seen filters for both the load and lamp side, so you may need to try both.

Hi Ed,

In my experience, conventional filters on the line side are less effective (often ineffective) if the mechanism is common mode. Remember that the definition of common mode for us is very different from that in the AC power world, where they are talking about voltage between neutral and green, and we are talking about current longitudinally along the cable. Indeed, the RF current is often on the Green wire (thanks to improper or missing bonding inside the noise source), and the Green wire goes right through commercial filters.

Our definition is what radiates, and in my experience, is most effectively suppressed with a multi-turn ferrite choke with all three conductors passing through the ferrite.

73, Jim K9YC
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