[AMPS] Chokes

[Radio WC6W]

On Mon, 13 Mar 2000 10:21:47 -0500 "Tom Rauch" <w8ji@contesting.com>
writes:

Hi Tom,

>Heating is always more of a problem than saturation, because of 
>the finite Q of soft-iron cores. The usual exception is pulse duty. 
>Most off the shelf rods have too much loss tangent at HF. They 
>look like a resistor in series with an inductor. 
 
   Yes, which certainly disqualifies them for a hi power resonant
circuit.  The article described a loosely coupled non-resonant
application. 


>If you tell me the core material type number (assuming it is a 
>standard number), I can tell you the Q or ratio of resistance to 
>reactance. I'd bet it is pretty poor with an off-the-shelf rod at the 
>high end of HF.  

  I would have posted it, if either the article or the Lafayette catalog
disclosed it...the Lafayette number was 32C6102 -- 1969 catalog p. 246.

  Do you want to hazard a guess that it was type 61, since all three
parts listed in that section have "61" in the number??

>The "dc" flowing through the core is time-varying at an RF rate. I'm 
>afraid no matter what the impedance, you are stuck with a certain 
>number of ampere-turns that are changing at an RF rate. 

>It always translates to volt-turns at a certain impedance, or ampere 
>turns at a certain frequency. Q of a resonant system multiplies the 
>problem because of increased VAR power.

  I don't have any formulas for flux density in rods... do you have a
reference?


>I would be skeptical of using random ferrite materials in a HV, high 
>current application at RF. Ferrites do not get rid of heat well.

  That's what the thermometer is for...  :-)

73,
  Marv  WC6W










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