[TowerTalk] VERTICAL BALUN
Ian White G/GM3SEK
gm3sek at ifwtech.co.uk
Sat Nov 5 13:32:19 EST 2005
>> Sorry, Tom, I have a big problem about using the term
>"balun" around any
>> antenna that cannot ever be "balanced" as you define it -
>and isn't even
>> intended to be.
Tome makes some fair points...
>That's fine. I agree it isn't a perfect name. It's a lot
>like Double Zepp.
>But if we don't call it a balun, we probably should stop
>everyone from calling the device that attempts to force
>equal currents on both symmetrical looking output terminals
>and has a coaxial input a current balun.
Wouldn't try to "stop" anybody anyhow, and certainly don't want to get
into a Holy War about it (oops, sorry Steve :-)
However, we do have to recognize that the same device has more than one
application, which is why one name won't fit all its uses.
If you're connecting it to a symmetrical antenna (such as a dipole) in
order to improve its voltage balance, then certainly I'd call it a
balun. But if the antenna isn't even supposed to have voltage balance
(such as a vertical GP) then calling it a balun is IMO misleading.
>Not that we have done that, what should we call that device?
>Un Un doesn't fit, because an un-un doesn't imply or often
>even have common mode isolation. Besides, the antenna also
>isn't perfectly UNbalanced. It's in a grey area between the
>land of balanced and unbalanced, just like many antennas we
>Should we rename the very same device for each application?
>80% balun? "Current Nearly Balun", or maybe "Current almost
>not a balun"? Send out stickers and some meters so users,
>depending on the load, can rename the universal device?
If we were starting afresh, "feedline choke" comes closer than any other
one name... but Marketing will instantly point out that customers expect
"BALUN" on the label, so that's what we get.
>> I agree completely with your definition of "balance" as
>> voltages from each conductor to the environment around the
>> But that definition categorically excludes any vertical
>antenna close to
>> ground. Such antennas cannot ever be balanced
>voltage-wise, and they
>> aren't intended to be. There's nothing a "balun" can do
>for such an
>Well, that isn't true.
Sorry, my last claim was not well expressed. What I meant was, if the
antenna isn't intended to be balanced in the first place (that's
*voltage* balanced, remember) why are we calling this thing a "balun"?
Not particularly disputing your other points either, Tom, but I've
already slept on this one, and then spent the day working, so if I don't
hit "Send" soon, it'll slip till Sunday. Let's cut to the key point
which is in your final sentence:
> as people I'm
>communicating with know what it really is.
The people I'm communicating with often don't... and that makes all the
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
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