[RFI] Galaxy Grow Light Ballast Update

[Jim Brown]

While I understand your intent, I don't agree with your execution. The 
problem is one of safety. The purpose of the Green wire in electrical 
systems is to blow a fuse or breaker in the event of a fault. That's a 
current path between Phase (hot) and Green, a differential path. When 
all three wires pass through the same choke, the choke has no effect on 
the differential current that blows the fuse, so the fuse blows quickly 
and reliably. If, however, there are separate chokes on Phase and Green, 
as in your circuit, the two chokes DO interfere with that fuse blowing, 
so it creates an unsafe condition.

73, Jim K9YC

On Mon,2/1/2016 9:45 AM, Tom Thompson wrote:
> 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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>