[RFI] Nutone Intercom problem

Pete Smith Pete Smith <n4zr@contesting.com>
Sun, 07 Jan 2001 21:19:08 -0500

At 04:44 PM 1/7/01 -0500, Palomar Engineers wrote:
>We stock "split-bead" ferrites that work on intercoms. This is a common
>problem and usually can be solved by putting the beads over the wires
>entering the main "electronics box". The principle is that the long wires
>going to the slave units pick up the RF and bring into the box containing
>the active amplifier circuits. Yours is the first we have run across with
>flat ribbon cable; all others have been multi-wire bundles. We stock a
>split for flat cable up to 2-1/2" wide. The nice thing about this approach
>is that if it doesn't help you can remove it without a trace. Adding
>capacitors, on the other hand, usually means soldering and "modifying" the
>equipment. Let the manufacturer's tech do that.

Don't split bead ferrites generally lack sufficient inductance to be much
use at HF, unless you're able to make several turns of the cable through

73, Pete N4ZR
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