Cores are good for flux density, not power level. It is a myth that
certain cores handle certain power levels. Change the circuit, and
the rating varies wildly.
1500 watts in a tank with a Q of ten is like 15 kW in a broadband
circuit.
Toroid cores are problems in high power resonant systems with
high Q.
> I am beginning the process of winding some toroid coils that are going to
> be used in a 1500 watt hf amp. The cores are T-225 and are supposedly good
> for 1500 watts but I figure to be safe I will use two sandwiched together.
> Questions:
>
> 1. Do the two toroid cores need to be insulated from each other or can I
> just place them tightly next to each other and then wrap them as a
> package?
I'd back up and calculate flux density with the VAR (volt-amperes
reactive) power of the tank, not the RMS power. You might find you
need fire-proof tape.
Generally by the time you get enough cross sectional area in the
core, you save very little space over an air core in hi-Q resonant
systems, and spend more money. Toroid cores are great in L
sections that operate with a Q of two or three.
I'd be especially sure to calculate flux density and heating if you
don't want to chase the tuning knobs around all day after long
transmissions. The core will overheat long before they saturate.
73, Tom W8JI
w8ji@contesting.com
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