[Boatanchors] Ferrite Choke

Mon Jul 16 11:35:47 EDT 2012

I guess you now acknowlege "a good paper on the subject that goes into a
lot of detail" that I posted here LAST WEEK:

"---------------------------- Original Message ----------------------------
Subject: Re: [Boatanchors] Ferrite Choke
From:    "J. Forster" <jfor at quikus.com>
Date:    Fri, July 13, 2012 1:25 pm
To:      "Jim Wiley" <jwiley at alaska.net>
Cc:      "Keith Densmore" <kmd at xplornet.ca>
         boatanchors at mailman.qth.net
--------------------------------------------------------------------------

A 'sleeve-type balum' may need a lot more than ten.

http://ebookbrowse.com/baluns-w1his-pdf-d286062338

-John

==============="

> As Im sure Gary is aware there is a lot more to creating a good common
> mode
> choke than just winging it without understanding what is involved.
>
> Ive had good results with a HP-4815A Vector-Impedance meter. By good I
> mean
> acceptable to my needs realizing the possible measurement errors from
> strays.
>
> Here is a good paper on the subject that goes into a lot of detail. There
> are errors in his measurements that have been covered elsewhere and the
> number of the large ferrite toriods can be substantially reduced.
>
> http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf
> ----- Original Message -----
> From: "mac" <w7qho at aol.com>
> To: <garyschafer at comcast.net>
> Cc: <boatanchors at mailman.qth.net>
> Sent: Monday, July 16, 2012 12:03 AM
> Subject: Re: [Boatanchors] Ferrite Choke
>
>
>> Hi Gary, it's ben a while....
>>
>> Yep, I know all that.  Special considerations concerning radiation
>> pattern,noise or
>> RF feedback existing or anticipated then OK.  For normal Ham
>> installations, though, just give it a
>> simple first try and maybe save yourself some effort and expense.  In
>> my personal experience
>> baluns, ferrite beads and tubes, etc. at wire antenna feed points or
>> not never made
>> a significant difference in what I could hear and who I could work.
>>
>> In the game since 1951
>>
>> Dennis D.  W7QHO
>> Glendale, CA
>>
>> ***************
>> On Jul 15, 2012, at 6:05 PM, Gary Schafer wrote:
>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
>>>> bounces at mailman.qth.net] On Behalf Of Ron Youvan
>>>> Sent: Sunday, July 15, 2012 8:30 PM
>>>> To: boatanchors at mailman.qth.net
>>>> Subject: Re: [Boatanchors] Ferrite Choke
>>>>
>>>>   Dennis D.  W7QHO  mac wrote:
>>>>
>>>>> Might be interesting to put the antenna up without any choke or
>>>>> ferrite and see how it works out......
>>>>
>>>>
>>>>   That is all that existed B 4 antenna baluns were created.
>>>> The advantage of any kind of balun at the feed point of a dipole is
>>>> to
>>>> prevent a nearby object to
>>>> one half of a dipole from unbalancing the antenna.  If it is equal
>>>> lengths and really in the free
>>>> and clear it does nothing of any great use.  Baluns can be made with
>>>> powered iron also cores.
>>>> --
>>>>    73 Ron KA4INM
>>>
>>> Consider that a coax cable feeding an antenna is actually 3 wires.
>>> Two inner conductors (center wire and the inside of the shield) and
>>> the
>>> third conductor is the outside of the coax shield.
>>>
>>> When connected to a balanced antenna, the center conductor is
>>> connected to
>>> one side of the antenna and the other side of the antenna is
>>> connected to
>>> the inner shield and the outer shield.
>>> That makes the antenna have one leg on one side and two legs on the
>>> other
>>> side, one being vertical (the coax).
>>>
>>> This unbalances the antenna and causes current to flow on the outer
>>> shield
>>> of the coax which acts as part of the antenna.
>>>
>>> It may work very well in this configuration as many have for lots of
>>> years.
>>> The disadvantage is the vertical part can pick up more noise and put
>>> RF back
>>> into the shack on transmit. It disrupts the dipole pattern if you
>>> care about
>>> that.
>>>
>>> The commonly used balun acts as a choke to isolate the outer coax
>>> shield
>>> from the leg of the antenna that is connected to the shield.
>>>
>>> 73
>>> Gary  K4FMX
>>>
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>
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