[Elecraft] how did I calculate the loss?

[John Buck]

Don Wilhelm nicely stated views similar to mine on the use of baluns. 

It should also be noted that many baluns are very lossy at other than 
the design load termination impedences.  For this reason I tend to use 
air wound coils of coax where I absolutely feel the need for a balun 
with a multiband wire antenna.  I admit that my Force 12 beam antennas 
use the W2DU type baluns at the antenna end of the coax.

Depending on the antenna, so what if the feedline radiates a bit?  When 
used with typical compromize wire antennas, feedline radiation may even 
help in some cases.
Feedline radiation is not loss if you consider the feedline to be part 
of the antenna.

For example with an inverted V antenna feed line radiation my just 
improve the vertical component of the antenna radiation, more like a top 
loaded vertical.

I have had stray rf in the shack as the result of unbalanced feedlines.  
In that case an airwound  balun in the attic away from the radio has 
solved the problem. 

I use both the K2-100 and the Orion with an SB220 amplifier and with no 
RF problems.

73,
John KH7T

Don Wilhelm wrote:

>Vic and all,
>
>I respectfully disagree.  The balance or lack of balance is dictated by the
>antenna system itself (and the RF will be independent of grounds).  So, if
>the antenna system is inherently balanced, the currents (or voltages if you
>prefer) on the feedline will be equal and opposite no matter what the drive
>is - this is not dependent on a balun or lack of a balun anywhere in the
>system.
>  
>

snip

>The real reason for a balun at the feedpoint of an antenna is to keep the
>current from flowing down the outer side of a coax shield. 
>
snip

> OTOH, if "RF in the shack" is a problem, a balun at the
>transmitter (or tuner) output may cure it.
>
>73,
>Don W3FPR
>
>----- Original Message -----
>
>  
>
>>I forgot to add...wouldn't you also need a balun at the antenna
>>feedpoint?  If you connect the feedline directly to the antenna the
>>currents in the legs of the feedline could be unbalanced and then you
>>might have significant loss from feedline radiation.
>>
>>    
>>
>
>
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