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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