[RFI] source for RFI filter cordset?

Tue Aug 2 14:35:09 EDT 2005

Martin,

There are two problems:  limited market (how many potential customers exist
for the type of filter you seek), and varied applications.

Some victims of RFI can do very well with the standard available filters
from CorCom and others, as described by N8SS in another posting.  Take a
good look at the specs on those filters; some will actually have a fair
amount of attenuation in all or part of the HF region, others just begin
attenuation at or near 30 MHz.  Power filters with "serious" attenuation
below 30 MHz require more core material and larger values of by-pass caps
than those intended for 30 MHz and above applications.  So, there is a
premium to pay for parts.

Those who find the "good" ones at hamfests should count themselves lucky.
Having worked for more than a decade at a company that made power line
filters as one of its (industrial and government) product lines, I can tell
you that the ICE filters are a very good bargain, indeed.

As for the surge supressors with filters, I can't say that any of those do
any good as filters at my QTH.  However, a ham friend of mine in the
northwest part of Iowa took a direct lightning strike to his tower and
antenna system last month.  All of his coaxial line and AC power line surge
supressors were destroyed, but his gear survived.  So, buy them as surge
supressors and take the "filtering" with a bit of salt.  If you check out
the specs on those power strips that include a filter, the filters are
intended primarily for the above 30 MHz region.

For these special applications, the choice is pretty much either pay the
premium price for serious filters (unless you get lucky at a hamfest or on
e-bay), or get good at homebrewing.

73, Dale
WA9ENA

             "Martin, AA6E"                                                
             <martin.ewing at gma                                             
             il.com>                                                    To 
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                                                                   Subject 
                                       [RFI] source for RFI filter         
             08/02/2005 10:49          cordset?                            
             AM                                                            

             Please respond to                                             
              "Martin, AA6E"                                               
             <martin.ewing at gma                                             
                  il.com>                                                  

Hello All,

I am tired of making improvised AC line filters by winding power cords
through ferrite cores for 6 or 8 turns.  They work ok, but they are
unsightly and oversized, especially if you have a 3-wire cord.

This should be a commercial product, don't you think?  I've searched
and haven't found one.  There are good RFI filters for IEC power
outlets and wired-in situations (e.g.
http://www.corcom.com/Series/IEC/EASEBS/ ), but I want one that is
compact and integrated with a cordset, so you just plug it in series
with your equipment's AC cord.  Even simpler: a box with the std
recessed IEC male with filter on one side and a 3-wire female outlet
on the other.   (I doubt that any of the premium "surge suppressors"
offer EMC filtering.  Does anyone know to the contrary?)

Yes, a box would be easy to make, but I want ready-made.  It's the
sort of thing that would cost you $12.95 at the hardware store if it
were produced in volume.  ICE has a box for $70+, but it is bulky and
too expensive for my application.

I'm thinking mainly of RFI egress (from consumer products to my
equipment), but this product would serve for ingress protection also.

Thanks for any pointers. Yes, I asked about this last year, but
nothing came of it.

73 Martin AA6E
--
martin.ewing at gmail.com
http://blog.aa6e.net
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