Brian,
Selecting the right bead is only the small part of the problem. The more
important part is knowing where to put the bead.
You didn't describe the noise other than that it is occuring at lower
frequencies. From this, my first assumption is that you are dealing with
switch mode power supply harmonics. They will sound kind of broadband and
occur ever 50-200 kHz or so. Anyway thats a good place to start.
As for the ferrite, the most common ferrite out there is some flavor of
Fair-Rite Type 43 with a permeability of 800-850. It is used by electronics
manufacturers for wideband noise suppression especially in the 20-200 MHz
range. It is the core you will find molded into or snapped onto common
electronics cables. It is also the most common core rolling around in the junk
boxes at hamfests. Though it is optimized for a higher frequency range it will
work at lower frequencies. Find the biggest one you can and then put as many
turns of cable on it as you can fit. When you find some improvement then you
can either add more turns, another core, or change to a different material to
optimize the results.
Good luck. Remember that consumer electronics are completely cost reduced and
many manufacturers will happily delete RFI suppression components because it
doesn't affect performance and most users won't notice the increase in RF
emissions.
Earl
N8SS
------------------------------
Message: 2
Date: Mon, 29 Jul 2013 13:07:04 -0400
From: Brian Sarkisian <cqkg8co@gmail.com>
To: towertalk@contesting.com
Subject: [TowerTalk] Wireless Internet RFI
Message-ID:
<CAKhJrARryLaHFfhO+LBEhS-017NypUAvCtjxn3REaRqsVqyi6A@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
I recently had an internet wireless antenna/unit installed as our DSL was
painfully slow.
Now I notice RFI in the AM broadcast band and into the 160 meter band.
There may more
RFI issues on other bands however at this point I haven't noticed anything.
I see that Fair-Rate makes a series of "New Low Frequency Suppression Cable
Component
ferrites, though I am not sure what I should purchase.
It looks like that I should be looking for a "certain impedance" for a
particular frequency.
Any help would be appreciated.
73 de Brian, KG8CO
------------------------------
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|