[TowerTalk] common mode chokes, baluns and multiband doublets

[Wes Stewart]

Nice of G3TXQ to so liberally quote my work:-)

I have a problem with W7FG recommending 4:1 baluns. 
(http://trueladderline.com/all-baluns/)  I suspect the thinking is that because 
the line is high impedance, the balun should be an impedance step up.  With a 
non-resonant dipole fed with open wire, the input impedance is just as likely to 
be lower than 50 Ohm and a 1:1 is more appropriate.

No need for me to elaborate, W8JI does a fine job: 
https://www.dxengineering.com/techarticles/balunsandfeedlinechokes/baluns-choosing-the-correct-balun

N7WS


On 12/11/2017 6:04 PM, Grant Saviers wrote:
> It seems there is a good solution to a single common mode choke for balanced 
> lines over all of HF.  See the article in November 2017 RadCom (RSGB) "An 
> effective, easily made HF Balun".  G3LNP describes a 4:1 balun for all band 
> doublets fed with REAL open wire feeders, with CM rejection on the order of 40db.
>
> Additionaly, consider G3TXQ's measurement of punched ladder line losses.  
> http://www.karinya.net/g3txq/wet_ll/
>
> I evangelize using real open wire, easy to make or buy. Examples:
>
> http://trueladderline.com/w7fg-design-600-ohm-open-wire-feedline/
> http://www.73cnc.com/product_p/ls100.htm
>
> Grant KZ1W
>
>
>
> On 12/11/2017 16:15 PM, Bert wrote:
>> We're talking about a common mode choke, not a balun/transformer.
>>
>> Bert, VE3NR
>>
>>
>>
>> On 12/11/2017 7:08 PM, Wes N7WS wrote:
>>> Actually that's not true. A lot of baluns are wound with balanced 
>>> transmission line.
>>>
>>> Wes. N7WS
>>>
>>> Sent from my iPhone
>>>
>>>> On Dec 11, 2017, at 3:49 PM, Bert <balmemo at sympatico.ca> wrote:
>>>>
>>>> Hi Bill,
>>>>
>>>> Choking the window line is not a good idea - you'll choke the signals too. 
>>>> Common mode chokes are mainly used for coax cables and multi-conductor 
>>>> cables. I'm sure you'll get many more detailed replies from the experts.
>>>>
>>>> Good Luck!
>>>>
>>>> Bert, VE3NR
>>>>