Hi Chris,
115 uH appears to be very much for 137 kHz. Not sure what type of filter
you are using but the standard filters use j50 Ohm which is 59 turns on
a T200-2 if i remember correctly. I passed 1.5 kW through such type of
filters and the caroe became maybe just 60 C warm.
So with a T225-2 you should have no problems at 2.5 kW :-)
For an air coil you will need more wire and will have more losses unless
you choose a big RF litz wire. But the size will be extreme and there
should be no lossy things in a radius of the length of the coil.
I would build a LPF based on j50 Ohm coils and -j50 Ohm Cs (~ 22 nF at
LF) and use the T225-2 cores.
73, Stefan
Am 24.05.2017 16:47, schrieb Chris Wilson:
Hello LF'ers,
24 May 2017
If I run the combiner on my 2 amps the LPF centre toroid heats up. I
made a silly mistake with setting my U3S driver the other night and
instead of TX'ing every 30 minutes it went on an every two minute
rampage before it soon self halted. The centre toroid winding has lost
most of its enamel coating and the Kaptan tape is crispy. It no longer
functions as an LPF, and I suspect the T225A-2 toroid is compromised
in its crystalline structure, through the very high temperatures, now.
115uH seems to be the calculated figure, if not actually measured (73
turns 14 AWG enamelled wire) of the centre inductor. An air core coil
of similar inductance isn't THAT big, (at least not the size of a
"small car" as someone on a US forum estimated :)) Is an air cored LPF
viable, or do i need to look at different core sizes or materials?
Thanks. LPF is at:
http://www.w1vd.com/LPF.html
Thanks.
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