[Amps] Line Isolators for RF feedback

[R.Measures]

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