[RFI] choking the service line

[Aaron Kreider]

Has anyone ever tried covering the service line with tin foil, foil 
tape, or conduit?  That'd probably provide the best attenuation other 
than burying it.

Does anyone make a snap-on conduit?

If you had to guess, what range of impedances would a service line like 
have at 2-6 mhz?  Could it easily be as high as 500 or more ohms?    I 
think my power line/service line might be resonating at 2.3 mhz (and 
possibly also around 3.2 mhz).  Presumably where it resonates, it'd have 
the lowest impedance and best chances of ferrite suppression.

Aaron

On 9/9/2013 5:08 PM, Jim Brown wrote:
> On 9/9/2013 1:49 PM, Aaron Kreider wrote:
>> How much attenuation can I get for 2 mhz to 6 mhz, per choke, by 
>> using monster chokes (material 31, 1 inch ID) on the service line?
>>
>> What is the regular impedance of the service line at these frequencies?
>
> There's no good answer to this -- what I was hoping to do when I tried 
> that was to reduce common mode radiation by the service line acting as 
> an antenna, and radiating to my antenna directly above and parallel to 
> it.  It all depends on the length of that cable as a fraction of a 
> wavelength at every frequency of interest. Not only that, but if the 
> length of the cable causes it to be inductive at some frequnecy(ies), 
> the inductive component of the cores will cancel the inductive 
> reactance and the current could increase. :)
>
>> From page 31 (Understanding and solving RF...), it looks like I'd get 
>> around 32 ohms resistant at 2 mhz and 68 ohms at 6 mhz. 
>
When I tried this in Chicago, I had no good way to A/B test it, and I 
was never convinced that the choke did anything useful.  But I did want 
to show that it was perfectly safe to use chokes on feeders carrying 
large currents so long as both sides of the path passed through the core.
>
> 73, Jim K9YC