[TowerTalk] Beverage Questions

[Tom Rauch]

Long delayed echo on the reflector?

>  Sounds like a logical conclusion to me.
>  Find the LOWEST frequency at which you get
>  a dip and that is PROBABLY 1/4 WL, assuming
>  your analyzer goes low enough.  I use an old
>  HP-606 signal generator which tunes below the
>  AM Broadcast Band and RF voltmeter to
>  check transmission line lengths.  N4KG

You don't need to go that far.

Find the points where the low impedance or high impedance dip 
repeats.

How far apart are they in MHz?

Take the frequency spacing of the impedance "repeat", that is a 
1/2 wl!

Use a standard formula to calculate length!

Using that method, I can calculate the electrical length of a 2500 
foot cable to within a foot, using a generator on 7MHz!!!!

I can also measure the actual electrical length of my Beverages, 
which is different than modeling programs predict.

Just slightly misterminate the Beverage, and look for impedance 
repeats as you sweep it. The frequency difference between 
impedance repeats tells you the half-wave frequency of the 
distance to the "impedance bump" is, which is normally the far end.




73, Tom W8JI
w8ji@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com