[TowerTalk] CM. 43 vs 31

[Richard (Rick) Karlquist]

On 10/11/2017 9:32 AM, Jim Thomson wrote:
> Im looking at the detailed notes on the  fair rite site.   Im not seeing where type 43 works better than type 31  for freqs above 5 mhz.
> They all depict the opposite.   IE:   type 31 works better than 43  from 160m and all the way up to uhf..around 220 mhz at least.   RS is always higher with type 31.
> What am I missing here ?
> 
> Jim   VE7RF.

What you are missing is that Rp (meaning R parallel) is the pertinent
parameter for RF chokes.  Higher Rs tends to indicate lower Rp.
What you want is higher Rp.
Most network analyzers allow you to select to measure admittance
instead of impedance.  They then allow you to display the
conductance and susceptance at the marker frequency.  Conductance
is the reciprocal of Rp.  I characterized various ferrite
materials and found that 43 is better for Rp from 160 meters
to 6 meters than any other material I tested.

Rick N6RK