[RFI] Galaxy Grow Light Ballast Update

[Tom Thompson]

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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