Topband: T-antenna dimensions?

[wd8dsb at aol.com]

Hello Mike,
 
EZNEC model of a T configuration using a 50 foot vertical section  
indicates each leg of the T needs to be 61 feet long (total length of the  top of 
the T would be 61 x 2 = 122 feet), and this is based on resonant  frequency of 
 1.82 mhz.
 
Input impedance will greatly depend on the number of ground radials you  
use.  With perfect ground you should expect an input impedance of  
approximately 12.2 ohms.  With an average ground (no radials), you should  expect an 
input impedance of around 66 ohms.  With ground radials you will  have 
something in between, and as you add ground radials you will start  approaching the 
12.2 ohm value at resonance.
 
A good way to match the T to your transmission line with very low loss  in 
the matching network would be through the use of a simple L network.
 
73's
Don Kirk (wd8dsb)

 
 
In a message dated 1/17/2010 10:44:57 P.M. Eastern Standard Time,  
mrscience65704 at yahoo.com writes:

Now that  I can hear very well (Two 2-wire bi-directional Beverages), it's 
time for a  transmitting antenna. I want to play in the contest during 
January 29-31, and  time is running out to put up a transmitting antenna. I don't 
have a tower at  this time.

I have some trees picked out for a T antenna, between a  section of pasture 
where it's easy to lay down a lot of radials. I can have a  50' vertical 
section.

But I'm having trouble finding what the approx.  dimension of the 
horizontal portion at the top should be. Any advice would be  appreciated!

73,
Mike Waters
W0BTU



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UR RST IS ...  ... ..9 QSB QSB - hw? BK