[Boatanchors] Ferrite Chokes

[Geoff]

----- Original Message ----- 
From: "James Liles" <james.liles at comcast.net>
To: "Geoff" <geoffrey at jeremy.mv.com>; <boatanchors at mailman.qth.net>
Sent: Monday, July 16, 2012 4:09 PM
Subject: Ferrite Chokes


> Hi Carl:
>
> If you run the coax at a 45 degree angle from the antenna I believe you 
> can expect RF on the coax.  If the choke is at the antenna, the RF induced 
> on the coax will be reflected by the choke at the antenna and forced back 
> to the source.  Don't much care though, if the coax angle is within 15 
> degrees from 90 or over 1/4 wave away from the antenna.
>
> My suggestion to Keith was "if you are real fussy about your antenna" use 
> a balun at the antenna because it eliminated the RF on the shield problem. 
> And then if the coax was run away from the antenna at an angle that 
> deviates much from 90 degrees, add the choke at the entrance to the shack 
> to kill what is induced on the coax by the antenna.
>
> The balun at the antenna provides the first line of defense.  The choke at 
> the shack mitigates any induced current from the antenna to coax from 
> getting into the shack.
>
> Hope this and the last post make sense --- don't know how else to explain 
> it.
>
> Have a great day and Kindest regards Jim K9AXN
>
> -----------------------------Original 
> Message----------------------------------------- 
> From: Geoff
> Sent: Monday, July 16, 2012 1:16 PM
> To: James Liles ; boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] Ferrite Chokes
>
> It doesnt matter which way the coax is run, the first line of defense is 
> at
> the antenna unless you like the feedline to continue radiating.
>
> Wrapping the coax around 2 of Fair-Rite part 2631803802 at $6.94 each from
> Mouser will be more effective than twice the cost of snap ons.
>
>
> ----- Original Message ----- 
> From: "James Liles" <james.liles at comcast.net>
> To: <boatanchors at mailman.qth.net>
> Sent: Monday, July 16, 2012 1:09 PM
> Subject: [Boatanchors] Ferrite Chokes
>
>
>> Hi again Keith:
>>
>> Don't know how difficult it is to get to the antenna feed point but here 
>> is
>> a thought that you might entertain if you are really fussy about your
>> antenna.  Simply add a mast mounted or hanging  balun.  That way both 
>> halves
>> of the antenna wire will participate.  Couple of advantages.  The antenna
>> will be a bit less susceptible to noise and there will be a very slight 
>> bit
>> of gain from driving both wires.  Also would significantly reduce RF on 
>> the
>> shield --- wouldn't have to use the cores at the antenna.  If the coax is
>> not 90 degrees from the antenna, I would still use the snap on cores but 
>> at
>> the entry to the shack.
>>
>> Just a thought --- the cores will be just fine though.
>>
>> Good luck Keith and let us know how all works out.
>>
>> Kindest regards Jim K9AXN
>>
>> --------------------------  Original
>> message ----------------------------------------
>>
>> Message: 1
>> Date: Mon, 16 Jul 2012 11:25:36 -0400
>> From: "Keith Densmore" <kmd at xplornet.ca>
>> Subject: Re: [Boatanchors] Ferrite Chokes
>> To: <boatanchors at mailman.qth.net>
>> Message-ID: <FC2A0A80A16645AABA4B7B15F935A631 at keith3dc125020>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>>>> Might be interesting to put the antenna up without any choke or
>>>>> ferrite and see how it works out......
>>
>>
>> Thanks to a kind suggestion from one of the list members, I have ordered 
>> a
>> set of beads from Palomar. The advantage of these is I do not have to
>> disassemble the coax connectors to install.
>>
>> I used to use a multi wire dipole without balun, located not too far from
>> the house without any RF feedback issues. Not so with the Off center fed
>> dipole which is totally unbalanced, and without a choke causes lots of RF
>> back into the shack. I guess there is no such thing as 'free lunch'.
>>
>> 73
>>
>> Keith ve3ts
>>
>>
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