[TowerTalk] Beverage impedance change in cold WX solved

[john at kk9a.com]

How important is the matching transformer on a Beverage? I am not a RX  
antenna guru, I only have installed simple temporary contest Beverages  
any place where I could hang the wire in desired directions.

John KK9A


jimlux wrote:


On 1/22/20 1:18 PM, VE6WZ_Steve wrote:
> Thanks Jim!
>
> I didn't look at the Fair Rite catalog, but yes…its there on page 8.  
>  I am using 73 material Binocular cores.
>
> The temp. coefficient for 73 material is .65 % per deg C.  My temp  
> change is about 50 deg C, therefore the permeability will change 33  
> % !!
> That seems like a decent amount.
>

Go to page 28, and there's a curve of properties vs temperature. It
looks like mu is 1500 at -40C and 2100 at 0C  (that's at 10kHz, where
mu'' (the loss) is very low.

The impedance at 10 MHz changes from about 80% at -40 to about 90% at 0
to a peak of 100% at 30C.