[Elecraft] [K3] Issue with HI CUR on 12m

[John Oppenheimer]

Hi Jim,

For high power Balun Applications, most critical parameter is Ferrite
core loss which causes core heating. Core loss, parallel resistance
(Rp), can be computed from complex permeability data from Fair-Rite.

https://www.kn5l.net/Balun-CM/Balun31-43/
Models FT240 10T with 31 and 43 materials. G.Zo is selected to indicate
maximum possible core dissipation watts. Maximum core dissipation
accrues when ground to antenna external conductor electrical length =
1/2 wavelength multiples. 1/2 wavelength multiples reflects ground
impedance to the Balun.

As shown, at 1.8MHz, maximum core dissipation for 1kW key down could be
4W for 31 material and 3.6W for #43 material. Probably not enough
difference to worry about.

The two CMRR traces, red and yellow, are below about -20dB. Difference
in choking ability is insignificant in this range.

The model includes a parallel capacitor for self resonance. Though is
not critical, as reactance does not result in heating. Core loss, Rp,
causes core heat rise.

All in all, not much difference between 43 and 31 for these two Baluns.

John KN5L

On 10/12/20 9:05 PM, Jim Brown wrote:
> #43 is a terrible material for the HF 
> bands.