[TowerTalk] common mode chokes, baluns and multiband doublets
wes_n7ws at triconet.org
Tue Dec 12 15:22:24 EST 2017
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:
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.
> I evangelize using real open wire, easy to make or buy. Examples:
> 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
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