[Elecraft] OT on balun usage

[Barry LaZar]

Bob,
     You are quite correct, and your recommendation to use a balun rated 
at higher power levels than you plan to run is dead on. One point; in 
the main, it is better to use a current type rather than a voltage 
balun. Between your recommendation and my suggestion, a number of 
problems get addressed and need not be of bother to the average ham.


73,
Barry
K3NDM

------ Original Message ------
From: "Bob McGraw - K4TAX" <rmcgraw at blomand.net>
To: elecraft at mailman.qth.net
Sent: 10/25/2015 8:41:06 PM
Subject: Re: [Elecraft] OT on balun usage

>One point I've learned over the years is the fact baluns, regardless of 
>the ratio, are power rated at matched values.  i.e. a 1:1 is typically 
>a 50 ohm to 50 ohm while a 4:1 is nominally a 200 ohm to 50 ohm device. 
>  And the power rating is mostly at closely matched values.  Hence a 4:1 
>balun is good for feeding a 1/2 wave folded dipole which, at nominal 
>height above ground, is about 200 to 300 ohms where as a 1:1 balun is 
>good for a 1/2 wave dipole at near resonant frequency.
>
>Therefore a 4:1 balun may be good for say 1KW if the Z's are correct.  
>Try to use one on a complex reactive load and the 1KW rating fails 
>rather quickly.  For that reason, for any balun I use and choose, it  
>is rated at 5x to 10x the expected power.  Thus a 1KW balun is good for 
>about 100 watts.    I recently "smoked badly" a 4:1 known brand 5KW 
>balun on 160M with my AM transmitter at legal limit when I connected 
>the 80M folded dipole antenna in error Shouldn't have done that.   The 
>transmitter didn't care but lots of smoke came out of the balun box.
>
>73
>Bob, K4TAX
>
>On 10/25/2015 2:57 PM, Fred Jensen wrote:
>>Yep, almost.  The word "balun" is a portmanteau of "balanced" and 
>>"unbalanced."  They are transformers or auto-transformers and their 
>>job is to keep a balanced feed to the antenna balanced when 
>>transitioning to unbalanced coax.  Since they're transformers, they 
>>can also transform the impedance.
>
>
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