[TenTec] ORIONII_INTERNAL_AT_TUNER--re:4:1 balun....hmmmmmmmm....

[CROCDONZ1@aol.com]

as told in world radio......
 
 
Important  Notice;  WHY USE  A  4:1 BALUN 
Krusty Olde Kurt is  now going to repeat himself.  Why? Because the same 
question keeps coming  up over and over. And he wants everyone to get it right.  
"I'm feeding my  dipole with 600-ohm line.  At the station end I need a balun 
to convert to  50-ohm coax. I need a 12:1 balun, right?"   Wrong!  A 4:1 
balun would be better. 
Why is  that?  If your dipole is up, let's say, 35 feet then on 80 meters it 
will  probably have a resistance at resonance of about 40 ohms. The actual 
resistance  depends on the height above ground in wavelengths.  
If the dipole is 40  Ohms then what do you see at the transmitter end of your 
600 ohm line? If the  line is a half-wave long (120 ft on 80 Meters) you'll 
see 40 ohms.  Remember, a half-wave line repeats what it sees at the other end. 
 But if it is a quarter-wave long you'll see 8500 Ohms!  At other line  
lengths you'll see impedances somewhere between these two extremes. 
So you are not going  to see 450 ohms at the end of your 450-ohm line. That 
only happens if you have a  500-ohm antenna hooked onto it. With such a 
variation in impedance at the  trans­mitter end of the line there is no one balun 
transformer that will  match it. Most of the time the impedance will be above 
the 50 Ohms of your coax  so a high impedance balun would be desirable.  
Unfortunately high  imped­ance baluns don't work well when not matched.    
Experience has shown  that 4:1 baluns work best in this service.  They are 
more  rugged and will take bad mismatches especially if they are wound on an 
iron  powder core.  So stop searching for that 12:1 balun. Use a 4:l BALUN and  
your system will work great.   
You can read  Kurt N. Sterba “AERIALS” column in World Radio  Magazine.  
don-kd9mf