[TowerTalk] Roller inductor sources

[TexasRF@aol.com]

The arguments about input vs. output baluns used with antenna tuners makes  
one wonder if a balun on both would be advisable?
 
73,
Gerald K5GW
 
 
In a message dated 10/19/2005 3:42:50 P.M. Central Daylight Time,  
cgerarden at atomix.com writes:

I must  respectfully disagree with Tom Rauch about the concept of a balun on 
the  output side of a tuner vs the input side. I currently have 4 tuners that 
I  have basically fried due to legal limit power and mismatches on 450 ohm  
line. These 4 tuners all had output baluns that saturated and got hot, but  
this is not always the failure point. Mostly HV failures at switches or  
caps. 

Only one tuner I have found works great in all 450 ohm line  mismatch 
situations. This is a Palstar 1500 BAL. It has 2 roller inductors  and a 
balun on the input. The inductors, in series with each side of the  output of 
the balun will match a 450 ohm line with high reactance very  well. It has a 
switchable cap to move it to the input side of the  inductors or output side 
for HI-Z or LOW-Z situations. 

Basically  the tuner completes the impedance transformation so the balun is 
not  stressed and will not saturate. Keep in mind I am talking about 
situation  like a shortened 80 meter doublet loading. 

A critical part of 450 ohm  line matching is to vary the feedline too. If you 
really want to match 450  ohm line use a balanced tuner like the Palstar 1500 
BAL. the T and L  networks are fine for coax line, but the secret is to 
provide a low SWR  into the balun output befor you connect it to the antenna.
this is all  based on real world testing. I have a stack of MFJ, Dentron, and 
1  Nye-Viking that I smoked. If you are only runing 100 watts, then almost  
anything will work, but with higher losses.  

Chuck
W0DLE
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