Re: [Amps] Line Isolators for RF feedback

[R.Measures <r@somis.org>]

On Aug 8, 2004, at 3:37 AM, Ian White, G3SEK wrote:

> R. Measures wrote:
>
> > > > Joe -- the only problems that I have heard of is the ferrite beads 
> > > > getting so hot they cracked and dropped off.  This is hardly 
> > > > surprising since the ferrite material that is typically used in 
> > > > bead baluns is rated by the manufacturer (not by the seller, mind 
> > > > you) at 1MHz maximum,
> > >
> > > That "frequency rating" is only for resonant circuits, and does not 
> > > apply to baluns. For balun applications you need the "wideband" 
> > > rating - this *starts* at 1MHz typ and extends up to 50-100MHz 
> > > according to the grade of ferrite.
> >
> > This is according to the seller or the manufacturer?
>
> The major manufacturer - see www.fair-rite.com

> > Permag Pacific is a manufacturer, and their catalog says  Nothing 
> > about different frequency ratings for one-turn (bead-balun) 
> > applications and multi-turn applications.
>
> I haven't seen their data, but in the Fair-Rite data you will find the 
> relevant information under the heading of "EMI Suppression". This is 
> because the balun and interference suppression applications share the 
> same objective: to create a high impedance along the wire/cable 
> passing through the bead.

The signal levels involved in RFI to receivers is not the same as the 
signal levels encountered in a transmitting baluns.
  ...
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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