A quick check shows that no small size cores will work for -43 material
with 10T at 1.8 MHz and 200W. However, FT50B cores come close, and are
fine at 3.5 MHz. FT50B is twice the thickness of the FT50A, and would
fit on the board because the thickness would only add height.
73,
Larry N8LP
Linden, Mike (BRC-Hes) wrote:
Larry,
If you have the time, I'd certainly appreciate it if you'd run it
through your spreadsheet for me.
Thanks! -Michael
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You have a couple options. The flux density is higher, and therefore
heating, with lower number of turns. They also go to a -43 mix (higher
permeability) for the lower turns to keep the shunt reactance of the
voltage xfmr high at 1.8 MHz.
If you don't care about 1.8 MHz, you might be able to get by with 10
turns on the -61 cores... I would have to do the math. The other option
is to stick with the -43 material, but get larger cores. I'm pretty sure
they make the FT50A and FT50B (which are thicker) in -43 material, or
you could go to a FT68 or FT82 if they'll fit. The best bet would
probably be FT50A-43, since we know it would fit physically. I have a
spreadsheet that I use that calculates these things for me... I can plug
these in to see what would work if you like.
73,
Larry N8LP
Linden, Mike (BRC-Hes) wrote:
Does anyone know what modifications would need to be made to the CP1
Directional Coupler in order to get it to handle 200W at 20dB
attenuation?
I'd like to use the CP1 as a cost effective means of extending the
useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more
attenuation than I want and the power handling at 20dB is not high
enough.
Thanks, Michael N9BDF
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