[TowerTalk] Beverage impedance change in cold WX solved

[john at kk9a.com]

Interesting Jon.  I imagine that a Beverage is like a Yagi in that it
basically wants to work but it can be fine tuned for better efficiency.  I
have never checked the impedance of my temporary Beverages which
use comercial K9AY 9:1 transformers.

John  Kk9A

Sent via the Samsung Galaxy 7 edge, an AT&T 4G LTE smartphone.


On Thu, Jan 23, 2020 at 8:16 AM Jon Zaimes <jz73 at verizon.net> wrote:

> John,
>
> I have, when a transformer had blown and I didn't have a spare handy,
> hooked the coax center conductor up directly to the Beverage wire. Output
> will be down due to the mismatch, but it still works like a Beverage.
>
> There may be more common mode pickup of signals on the feedline since the
> transformer is no longer there to isolate it from the antenna.
>
> 73/Jon
>
> Jon P. Zaimes, AA1K
> Tower climber for hire
> http://www.aa1k.us/
> Cell: 302-632-2353
>
> Reviews of AA1K tower work on eham website:
> http://www.eham.net/reviews/detail/12922
>
> Hug your favorite tower every day, and always stay connected to it.
>
> -----Original Message-----
> From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of
> john at kk9a.com
> Sent: Thursday, January 23, 2020 7:39 AM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Beverage impedance change in cold WX solved
>
> 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.
>
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