[TowerTalk] Beverage impedance change in cold WX solved

[Jon Zaimes]

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.

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk