[RFI] Vibrating Ferrite Chokes on Service Line

[Aaron Kreider]

Jim,

Thanks for the feedback!

Unfortunately the lines are too big to fit through a single ferrite.  
Does anyone make a ferrite choke with a 2.5 inch inner-diameter?

Otherwise I'm working on finding better positions for my antennas, 
getting my phaser setup, and one-day I'll canvass the neighborhood (and 
see how many people let me walk through their apartments). There are 
lots of neighbors and lots of student renters - so I might have to do 
this every year.   And there are a lot of people I don't know.

What do you think the biggest danger is?  They didn't get noticeably 
warm.  So maybe the wear and tear on the service line? There aren't any 
trees nearby.

Aaron


On 7/12/2015 11:22 PM, Jim Brown wrote:
> On Sun,7/12/2015 7:00 PM, Aaron Kreider wrote:
>> So I finally got around to putting monster chokes on the service line 
>> that feeds my house and several neighbors.  3 chokes on each line 
>> (positive, negative, and neutral) with zero turns 
>
> One pass through a core is one turn.
>
>> (as the wire is too thick).  It decreased my noise on 492 khz from 50 
>> uV to 42 uV (*probably - there is some uncertainity as the level of 
>> noise varies presumably due to electricity usage  -- currently it is 
>> at 62 uV*).
>>
>> The 492 khz is a 9th harmonic of the 49.5 khz fundamental rfi source.
>>
>> The unexpected thing was that the chokes vibrated and made a loud 
>> buzzing noise that can be heard 40 feet away (even over modest street 
>> noise).  This was very concerning at first, until I looked it up 
>> online and found that this is normal behavior.
>
> They should vibrate -- you're hitting them with lots of current! This 
> is NOT a proper application of ferrite chokes.!
>>
>> Jim Brown - you might want to include information about choke 
>> vibration in your very informative guide.  I searched it for "vibrat" 
>> and didn't find any mention of this phenomena.
>>
>> Anyways, I removed the chokes - because I'm concerned that the 
>> vibration would damage the insulation on the service lines.
>
> I need to add advice not to put chokes on individual lines. :)
>
> When all three conductors go through the chokes, the net flux is near 
> zero. When only one goes through the choke, the flux can be HUGE, and 
> probably saturates the core.
>
>>
>> The chokes also became strongly magnetized, making them harder to open.
>>
>> The choke on the neutral line vibrated a lot less than the others.
>
> Yup, because it usually carries much less current.
>
>>
>> Is it safe to have the vibrating chokes on the service lines? 
>
> No.
>
> 73, Jim K9YC
>
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