[Elecraft] CP1 Power Handling

[Larry Phipps]

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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