[TowerTalk] current balun question

[Máximo EA1DDO_HK1H]

Guy, my question is NOT about common mode current.

Is NOT about how much impedance a choke provide.


My only question is to know if (and how) a "common mode choke" is able to balance different "differential currents".


Do you remember the famous I1, I2 and I3? Where I3 is the common mode current the choke suppress.

So ,my question is about I1 and I2.

If I1 and I2 are different values at feed point, Is a choke balancing them? Make them equal values into the coax (not antenna side, only coax side) ?

Or a choke has no effect in I1 and I2 differential mode currents?


Thank you


73, Maximo

________________________________
De: guyk2av at gmail.com <guyk2av at gmail.com> en nombre de Guy Olinger K2AV <k2av.guy at gmail.com>
Enviado: lunes, 20 de marzo de 2017 11:08
Para: Máximo EA1DDO_HK1H
Cc: k2av.guy at gmail.com; TowerTalk at contesting.com; jim at audiosystemsgroup.com
Asunto: Re: [TowerTalk] current balun question

Well, if your rendition of the theory is that actual zero common mode current (complete suppression) is impossible, and the equation delivers a *degree* of reduction of common mode which can't be solved until you know *how much* choking a device has, then you have a practical grip on the theoretical. You will always be asking "how much" blocking instead of does it block or does it not.

The beauty of the standard model of particle physics (a theory) is that it quantifies grey areas and degrees of effect.

73, Guy K2AV

On Mon, Mar 20, 2017 at 6:56 AM, Máximo EA1DDO_HK1H <ea1ddo at hotmail.com<mailto:ea1ddo at hotmail.com>> wrote:

In my case, regarding my question earlier today, I don't need actually any choke or balun. I'm just trying to learn, the theory.


Thanks


73, Maximo

________________________________
De: guyk2av at gmail.com<mailto:guyk2av at gmail.com> <guyk2av at gmail.com<mailto:guyk2av at gmail.com>> en nombre de Guy Olinger <k2av at contesting.com<mailto:k2av at contesting.com>>
Enviado: lunes, 20 de marzo de 2017 10:51
Para: Máximo EA1DDO_HK1H
Cc: jim at audiosystemsgroup.com<mailto:jim at audiosystemsgroup.com>; TowerTalk at contesting.com<mailto:TowerTalk at contesting.com>
Asunto: Re: [TowerTalk] current balun question


On Mon, Mar 20, 2017 at 3:12 AM, Máximo EA1DDO_HK1H <ea1ddo at hotmail.com<mailto:ea1ddo at hotmail.com>> wrote:
By "effective," I mean a choke that has a very high common mode
resistive impedance at the operating frequency.

Indeed.

But this is THE monkey wrench in the works for a lot of folks, possibly including the original poster on this thread. On the lower bands, a lot of "all band" chokes have very little blocking. I've measured one as low as 173 ohms on 160 meters. Store bought devices vary all the way from cr*p to really very well done devices designed for specific purposes from Balun Designs, who in my mind right now is the Cadillac manufacturer of such stuff [disclaimer: no commercial interest here].

OCF applications put a very large strain on choking devices, and really must be done exactly right to stay away from loss. A few of us have accumulated a collection of amusing "flaming balun" stories from around the country, where the accumulation of heat in the enclosure eventually set all the plastic on fire.

"Honey, there's something on fire up on your tower. And it smells bad."

For a while the North Carolina chapter of PVRC, upon provocation, would present something called the N4AF Flaming Balun Award for various destructive RF faux pas. You can guess the rest.

Don't be looking for a cheeep way out, or to reuse a "junk box balun" that you can't think of any other use for, that you wish someone would tell you it's OK to use.

Go buy something MADE FOR the application and frequency. Then string it up and go have fun.

73, Guy K2AV