[Elecraft] Suggestions needed - antenna to tuner

[Bob McGraw K4TAX]

I've used balanced line systems and tuners and baluns for years. In 
general the 135 ft center fed wire with your choice of balanced line, I 
use the vinyl covered 450 line from The Wireman, will work quite 
well.    I bring the line from the feed point of the antenna all the way 
to the operating position where it terminated into the 1:1 current 
balun.  Balanced line of this type is not near as difficult to use as 
many will allude.   Just use common sense.  Be sure to use lightning 
protection on the line before it enters the house.

Regarding baluns, keep in mind that one is not "matching the line" i.e. 
450 ohms but the overall load Z.   Hence the better choice is the 1:1 
current balun and not the 4:1 as many seem to believe.    Also, 
understand that the design and rating of baluns is based on a matched 
operating condition on both sides of the balun.  The 135 ft center fed 
wire with balanced feed is in most cases far from matched.  Thus the 
balun should be rated for much higher power than one would ever expect 
to run.  In my case, for legal limit power, my balun is rated at 
10KW.    I do use BALUN DESIGNS products for my applications.  Be sure 
you select a balun which is designed to be used with a tuner as the 
voltage / current ratings will be different than those for matched 
applications.

What is a matched application for a balun?.  A good example is a folded 
dipole made of and fed with balanced line.  Typically the folded dipole 
Z is about 300 ohms regardless of line impedance. However, due to 
reasonable proximity to the earth, the impedance is more like 200 to 250 
ohms.   Hence a 4:1 balun is the ideal choice providing an unbalanced 
feed to the transmitter of about 50 ohms.

Here is a good source for real world applications and performance of 
baluns. http://www.dj0ip.de/balun-stuff/

73

Bob, K4TAX


On 2/12/2018 9:29 AM, David Bunte wrote:
> Alan -
>
> I am pleased with results I have gotten with units from BALUN DESIGNS.
> Their 1161 & 1171 models are possible choices. I know some folks would
> rather spend less and build their own, but if that is not your preference,
> then look at these models.
>
> Best of luck.
>
> 73 de Dave - K9FN
>
> On Mon, Feb 12, 2018 at 10:20 AM, Alan Lambert <alan at thelamberts.com> wrote:
>
>> MORE Info
>>
>> As is I can work 80-10.  Some bands are better then others but I can
>> work them all with an SWR in the 1:1  to 1.3:1  range.    The fed line
>> is 450 window. The dipole is center fed.
>>
>> On Mon, Feb 12, 2018 at 9:26 AM, Alan Lambert <alan at thelamberts.com>
>> wrote:
>>> I could use a little advice
>>>
>>> My present setup is;
>>> KX3 > KPA100 (w/ ATU)  >   MFJ Balanced line tuner  >  ladder line fed
>>> 80m Inv 'V'
>>>
>>> I run this with the ATU disabled and then manually tune.  Obviously
>>> this is time consuming and makes band switching a pain so I am
>>> considering removing the MFJ from the chain and start using the ATU.
>>> Also I plan to add a KPA/KAT500 in the near future and my MJF tops out
>>> at 300w so I has to go anway.
>>>
>>>
>>> The questions are...
>>>
>>> 1) Should I do it? or will I see a significant performance decrease?
>>>
>>> 2) If I do  -  How should I make the ladder to coax conversion? I
>>> think I need a "tuner balun"?
>>>
>>> 73
>>> Alan
>>> KN4BBC
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