http://elecraft.85.s1.nabble.com/ladderline-and-balun-question-tp7179004p7182660.html
> Don,
>
> If you don't have TLW, you might have to invest in the ARRL Antenna
> Book - it is on the CD that comes with that book.
> It is "Transmission Line for Windows", and you can plug in the antenna
> feedpoint impedance, the type and length of feedline and the program
> tells you the impedance at the other end.
>
> 73,
> Don W3FPR
>
> On 1/11/2012 5:11 PM,
[hidden email] wrote:
>> HI Don,
>>
>> I wish to look into the TLW application you mention. However, I am
>> not
>> what it is exactly. Would you please be so kind as to point me in
>> the
>> proper direction.
>>
>> I most likely will be going back to the 1:1 balun but the promise of
>> swr
>> of 1.3 on 160m was nice, which I have on the 4:1. Also it is a
>> current
>> balun.
>>
>> Thanks
>>
>> ~73
>> Don
>> KD8NNU
>>
>>
>> On Wed, Jan 11, 2012 at 5:02 PM, Don Wilhelm wrote:
>>
>>> Don,
>>>
>>> According to L B Cebik's modeling, a 2 wavelength horizontal loop
>>> will
>>> have a feedpoint impedance of 180 - j125 ohms, and a 4 wavelength
>>> loop
>>> (the same loop used on 80 meters will have a feedpoint impedance of
>>> 235 - j135.
>>> Both are good candidates for the use of a 4:1 balun - but that only
>>> applies if you mount the balun right at the antenna feedpoint. The
>>> fact that you have 60 feet of 450 ohm feedline changes the situation
>>> drastically - that is about 1/8 wavelength on 160 and close to 1/4
>>> wavelength on 80 - so the feedoint impedance at the end of that 60
>>> feet of feedline is quite a bit lower - that is most likely why your
>>> 1:1 balun worked so well. You can work with L B Cebik's antenna
>>> feedpoint impedances and the TLW application available from the ARRL
>>> to find the feedpoint impedance at the end of the 60 foot feedline,
>>> but I think you will find it closer to 50 ohms than to 200 ohms.
>>>
>>> The other question is what type of balun is your 4:1 balun - if it
>>> is
>>> a voltage type, it has no chance of stopping common mode current.
>>>
>>> My guess for why your current choke did not work is either that you
>>> did not place it at the right point on the coax, or it was at a
>>> point
>>> where the RF voltage was high, and in light of a high RF voltage
>>> (think impedance equal to 2000 to 4000 ohms, a choke of 5000 ohms
>>> impedance does not have much of a chance to stop any current.
>>>
>>> So bottom line - go back to what you had before, or put the 4:1
>>> balun
>>> at the antenna feedpoint where it should work if your antenna is
>>> anything like L B Cebik's simulations.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 1/11/2012 4:12 PM,
[hidden email] wrote:
>>>> Gents,
>>>>
>>>> I have a ladder line and balun question that I hope someone can
>>>> guide
>>>> me
>>>> thru.
>>>>
>>>> I had a good working antenna system with two antennas. First being
>>>> an
>>>> Alpha Delta Dipole and the second a 2WL 160m loop antenna at 40 ft
>>>> in
>>>> the air strung in trees. So the wire does touch the trees.
>>>>
>>>> Dipole is fed with coax and choked at the feed point and the loop
>>>> was
>>>> fed with 60 ft of ladder line to a 1:1 current balun then 25ft coax
>>>> to
>>>> the shack tuner. Then the amp and radio. This combination was
>>>> working
>>>> real well no RF problems in the shack.
>>>>
>>>> I was advised that I would obtain better results for better SWR at
>>>> resonance and easier matching if I removed the 1:1 balun and went
>>>> to
>>>> a
>>>> 4:1 balun. I made this change with everything else being the same.
>>>> I
>>>> now had RF in the shack again.
>>>>
>>>> I then added an isolation balun to the system by adding 6ft coax
>>>> from
>>>> the output of the 4:1 to a balun designs 116du which is supposed to
>>>> have
>>>> 4500 ohms of choking impedance on 160m and over 5000 ohms choking
>>>> impedance on 80 and 40 meters. This did not eliminate the RF and
>>>> I
>>>> am
>>>> still having problems.
>>>>
>>>> So here is the question, is it possible that with the combination
>>>> of
>>>> length of the ladder line at 60ft plus the 6 ft plus 25 ft of coax
>>>> I
>>>> am
>>>> at a feed line length that will be a problem no matter what I do.
>>>> I
>>>> keep looking at the internet to try and figure this out but I am
>>>> confused as some information I find says it only applies to 1:1
>>>> baluns
>>>> or other factors.
>>>>
>>>> So anyone who can help me understand this feed line question I will
>>>> be
>>>> greatly appreciative.
>>>>
>>>>
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