[Amps] Lowpass filter inductor cores

[Manfred Mornhinweg]

Hi all,

I'm puzzled by seeing many low pass filter boards offered on eBay and 
elsewhere, that are rated for 1kW, 1.5kW and even more, with some 
sellers stating that their filters can work in CW without requiring 
cooling; and these filters all seem to use T-130-2 and T-130-6 toroids. 
With the 10m coils having 5 turns on a T-130-6 toroid, and the 6m coils 
4 or even 3 turns.

I just did a small calculation, and if I'm not mistaken I get a flux 
density of around 30mT on the 30m band. Extrapolating the loss data 
given by Micrometals and Amidon for that iron powder material, it turns 
out that at 1500W output the core loss would be around 100W!!! And on 6m 
of course it would be worse. The inductors would get hot enough to 
unsolder themselves.

Either I did a mistake in my calculations, or it's simply not true that 
those filters can work at this power level, maybe not even with forced 
air cooling!

So my question is: Has anybody here actually used any of those filters, 
or the mentioned cores, at legal-limit RTTY, on the highest bands? How 
hot do the toroids get? With how fast air flow?

Manfred

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