[Amps] Line Isolators for RF feedback

[R.Measures]

On Aug 5, 2004, at 3:04 PM, Joe Isabella wrote:

> You're right, Rich -- bad wording...  My point was only that even at 
> 1.5-2kW, the PL-259s or coax
> they're soldered to would be first to go.
>
> I'll stick with my bead balun -- it fixed all the RF problems I was 
> having, so unless it bursts
> into flames, I'll keep it!!

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,
>
> And there was a group of us talking about this very subject the other 
> day.  How would one
> determine how much power could be run through a bead balun if I were 
> to build my own?  (Assuming
> enough ferrite to cover about 12 inches of RG-400).

-  Simple, jack up P until a bead cracks and drops to the floor.  A 
friend accomplished this with 2500w.  The bad news about ferrites is 
that they start generating harmonics long before the self-destruct.
>
> Thanks,
> Joe,
> N3JI
>
> --- "R.Measures" <r at somis.org> wrote:
>>
>>> Even say RG-400 or RG-303 would give up before they get saturated,
>>> right?
>>
>> Hello, Joe --  Coax doesn't saturate, it melts and/or ignites.  Cores
>> saturate.
>>
>>> Just curious --
>>> even if I ran my 3K-A at full bore, it wouldn't kill 'em (given that
>>> the dipole is at it's
>>> resonant point).
>>
>> A 3K-A will do about 2-out.  This should not be a problem for small
>> coax using SSB, especially because the choke balun is at the center of
>> the dipole - so it gets cooled by the breeze.  I make the choke balun
>> for a dipole out of the same coax used in the feedline because there
>> are no coax splices or connectors out in the weather and because the
>> balun would definitely be as capable as the feedline.  Sure, an
>> ugly-balun won't win any beauty contests, but it  Will  do the job.  
>> //
>>   The main weakness of an outdoor coax choke balun is that UV from the
>> sun deteriorates the nylon cable ties that are used to hold the coax 
>> to
>> the ABS sewer pipe.  A solution is to cover the nylon cable ties with
>> black electrical tape.
>> end
>>>
>>> Joe
>>>
>
>
>
> 		
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org