[Elecraft] my KPA1500 and 160M

[David Gilbert]

OK ... I'm going to make this simple for you.  Picture a material (like 
a capacitor) with a lossy dielectric, and then apply a high RF voltage 
across it.  The dielectric passes a current as the result of the 
voltage, and the lossiness of the dielectric generates heat. With a lot 
of voltage the heat generated can be considerable.

Now then, whether you want to acknowledge it or not, a ferrite core IS a 
lossy dielectric and can get hot when you put a high enough RF voltage 
across it INDEPENDENT OF THE CURRENT FLOWING THROUGH THE WINDING AROUND 
THE CORE.  You can find innumerable references to the dielectric losses 
of ferrite materials if you just bother to do some internet searching.  
This is NOT an insulation breakdown issue ... not at all.

All of this can happen as soon as power is applied to the system 
containing the ferrite.  Certainly the rate of temperature rise will be 
dependent upon how much voltage is applied, the frequency of it, and the 
dielectric loss characteristics of the particular ferrite, but VSWR is 
the voltage we're talking about here and that becomes relevant 
immediately upon application of power.

I suspect that you will dig in your heels and continue to dispute this 
basic physics, but at least I hope others here will understand things 
better than you do.

Dave   AB7E



On 9/2/2020 5:52 PM, Adrian wrote:
> I say that your response is completely false and you are missing basic 
> electricity facts. The high voltage becomes an issue when insulation 
> breaks down, and then *current *starts
>
> to flow through the fault path converting to emf & heat directly and 
> via induced current resulting ;  P = E X I*. *Without the current the 
> heat does not occur, it is basic physics, and
>
> the heat is directly proportional to the current. Voltage can exist 
> without current, but current cannot exist without voltage. Heat 
> produced is directly proportional to the current whether
>
> it be in the intentional circuit path, or fault path caused by high 
> voltage insulation breakdown..
>
>>
>> In addition, your statement that only current in the balun circuit 
>> can produce heat is completely false.  High voltage RF can create 
>> major core heating due to dielectric losses in the ferrite core 
>> independent of the magnitude of current flow in the tuning circuit. 
>> Several discussions on the TowerTalk reflector have pointed this out 
>> over the years for baluns and common mode chokes in ham radio 
>> applications.
>>
>> Dave   AB7E
>>
>>
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