[Elecraft] 9:1 Balun

[kevinr at coho.net]

We have all learned to say, "Yes Dear." and carry on.

     73,

         Kevin.  KD5ONS


On 1/31/2017 3:11 PM, Fred Jensen wrote:
> This list is a lot like being male and married ... no matter what you 
> do or say, you're going to be told you're wrong. [:-)
>
>> Most common baluns are *not transformers* as the energy does not pass
>> solely from input to output by magnetic coupling.  In fact, I would
>> hazard a guess that *none* of the devices advertised/sold as baluns
>> are transformers.  Yes, many of the inexpensive 4:1 "baluns" - the
>> voltage type (auto-transformer) baluns - may qualify due to the
>> magnetic coupling between windings but they are *not* baluns in that
>> they do not provide a balanced to unbalanced transformation (they are,
>> in your terms an "un-un").
> We were at our previous QTH on 5 acres for 38 years and I had a lot of 
> time and space to experiment with antennas.  I had or had used 6 
> different baluns.  All were transformers.  I currently have one on my 
> HOA-Stealth wire.  It too is a transformer.  I also have an unused one 
> in the garage that is an autotransformer with the shield carried 
> through to one of the terminals on the "other" side.  It is an Un-Un, 
> but it has a 4:1 turns ratio [16:1 impedance transformation] as well.
>
> While transformers are not the only way to build a bal-un or un-un, 
> that's 7 bal-uns and 1 un-un, all transformers.
>
> One can build a balun from transmission line since a transmission line 
> will act as a transformer.  They're frequency dependent of course, and 
> typically used at VHF and up.
>
> Incidentally, one of the transformer baluns with an SO-239 connector 
> carried a rating of "10 KW, 11 KV."  I don't think I'd want to stuff 
> 10KW into that connector. [:-)  I still have it, I'll never use it 
> again, I'll give it away if anyone wants it.
>>
>>> In the classic case, a balanced load [e.g. center of a half-wave
>>> wire] becomes unbalanced [coax, shield grounded] by the bal-un.
>>
> Again, NO!  The balanced load is not "unbalanced" by the balun.
>
> Did not intend to say that, English can be seriously difficult when 
> describing something.  Let's see if I can re-word that to better 
> convey the meaning ...
>
> "The balanced side of the balun is balanced, and it stays that way.  
> That's half the point of all this drivel [the other half is impedance 
> transformation].  They sometimes use standoff's or such for the 
> balanced connection.  Once you go through the balun toward the 
> transmitter, you get an unbalanced connection for the unbalanced coax, 
> usually an SO-239.  The balun thus allows a balanced load [e.g. the 
> center of a wire] to remain balanced when fed with an unbalanced 
> transmission line." That should help.
>
>> Due to skin effect, a properly terminated coaxial cable is a three
>> wire transmission line.  The center conductor and *inside* of the
>> shield form one circuit (which is "balanced" due to the laws of
>> physics) and the *outside* of the shield carries "unbalanced" (or
>> common mode) current due to any difference in potential between
>> the ends of the cable or induced currents from external fields.
>
> Yep, that fact has been discussed multiple times here.
>
> 73,
>
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
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