[TowerTalk] Force 12 Balums

[Dave_K9NX]

TOM
Depending on who you ask the purpose of the balun is to keep currents from
flowing in the outer braid of the coax and thus having the coax radiate and
possibly spoil the pattern or contribute to impedance match problems. Some
believe that the balun " balances the currents in the dipole arms and thus
gives a more uniform " pattern".  Some say both. 

In any case as a RF choke,I have measured coiled coax "baluns" with a Autek
RF-1 and they have a impedance on the order of 500 to 1000 ohms depending
on the construction and frequency. This should be enough to keep any
significant RF currents from flowing in the outer braid to cause impedance
matching problems and feed line radiation. Is the coiled coax  a "balanced"
device? Not likely. But I have used them for years and have worked 327
countries that way. IS my beam pattern perfect? Who knows! ... Who cares!
The coiled coax is virtually failure free, doesn't heat etc. You have to
take normal precaution (coaxiseal) to keep water out and that's about it.
As someone pointed out earlier use a good grade of RG-213 not the foam
dielectric stuff.

Oh and by the way the Force 12 manual lists this type of " balun" as one of
the recommended feed options. 

Dave 
K9NX

At 05:04 PM 11/7/98 -0800, Tom Osborne wrote:
>
>
>
>Dave_K9NX wrote:
>> 
>> Larry
>> 
>> 8 to 10 turns of coax 10" in diameter works fine, lasts long
>time.......... delivery time is usually overnight from thousands of
s>ources the cost is less than $5
>> In 20 years of using "coax coil chokes" I've never had one fail......
>> coaxiseal not included.
>> Dave
>> K9NX
>
>Hi Dave et al:
>
>This may sound like a stupid question, but how do we know a coil
>balun works fine.  How can you check to see if it is working?  If
>I put one on my antenna, what will it do different than if I
>hooked it up direct without a coil balun?  Thanks and 73
>Tom W7WHY
>
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