On one of my antennas, being single band, I have a 1:1 current balun at
the feed point of the antenna, top of the tower and some 75 ft of LDF 50
ohm coax direct to the tuner. Works great! Very low loss and will handle
all the power on a single band I can generate. Now then, single band
because the SWR gets out of bounds on other bands and the coax loss goes
up, noticeably. On certain bands/frequencies the SWR on the coax is
greater than 10:1.
Thus for the multiband antenna I use a balance feed of whatever impedance
one desires, mine happens to be 400 ohms, an a 1:1 current balun at the
tuner. Out of the tuner is about 12" of RG-213 from a coax output to the
balun input. But here again the balun is operating often in a circuit
with very high SWR. Loss in 12" of coax is negligible.
But the best yet is my home brew balanced tuner that uses a pair of
identical rollers, mechanically coupled and a variable C switchable as a
Lo Z L network or a Hi Z L network. Thus the transition from 50 ohms
unbalanced to 50 ohms balanced is always at a 1:1 SWR through the balun
network. Here with a balanced feed line being 400 ohm vinyl covered
window line and the antenna center fed, this system will handle all the
power efficiently one can generate on any band 160M - 10M.
Just remember the feed line from the antenna feed point to the
transmitter/tuner is some form of a line section transformer depending on
the complex impedances and electrical wavelength of the associated feed
lines. You are not looking a only one component for impedance.
73
Bob, K4TAX
> Interesting conversation!
>
> So what I am reading is this.
>
> Use a 1:1 current balun remote to the tuner to use my 600 ohm feedline.
>
> Now
>
> Somewhere along the way, depending on the length of the coax between the
> tuner and the balun, wouldn't I be just matching the say 14 foot run of
> coax from the tuner to the balun? And not necessarily matching the
> antenna?
>
> Lets take it one more step
>
> Place the 1:1 balun at the feed point 200 feet away and feed it with
> coax?
>
> Dosen't sound like a good idea.
>
>
> Mike wb8vge
>
> Sent from my iPhone
>
> On Jul 11, 2013, at 5:59 PM, "Robert Mcgraw" <rmcgraw@blomand.net> wrote:
>
>> Because your antenna impedance is not 600 ohms but is more lilkely 25
>> to
>> 75 ohms depending on height above ground. Only the feedline is 600
>> ohms
>> and that is really not an important issue.
>>
>> 73
>> Bob, K4TAX
>>
>>
>>
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I am a Tentec Ambassador and compensated according to the Tentec
Ambassador plan. I serve as a volunteer beta test person for the Omni
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