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quads ..rf choke ? ..help please ..

Nov 2, 2013
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5
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I am installing a new L2quad , I only want to put it up onceand want everything to be hunky dorey ...gonna use a couple of rf chokes for vertical and horizontal feeds ..do I install near feed on boom ..or would be better off a few inches down the mast ..?

thanks ..KP160
 

Nov 2, 2013
45
5
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As close to the feedpoint as you can. The less transmission line between the choke and the feedpoint the better.
AHH ..mr kilowatt to the rescue ..thanks sir , want everything good before I put her up in the air ..any other wee bits of advice will be much appreciated sir ..only want to do this once ...?
 

TB01

Member
Jan 27, 2011
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And use proper ones that have ferrites in them, not air wound ones.

New tower/beam project going on soon. Could you post a link on what ferrites to get? I've been on the fence about this subject some say air wound some say ferrite chokes. I'll probably go with lmr 400 flex
 

M0GVZ

Sr. Member
Oct 18, 2011
1,771
1,539
173
New tower/beam project going on soon. Could you post a link on what ferrites to get? I've been on the fence about this subject some say air wound some say ferrite chokes. I'll probably go with lmr 400 flex

Mix31. Don't go for unmarked ones. Fair-rite ones are good.

There is no discussion to be had with whether to go for air wound or ferrite chokes. Its as simple as this:

Air wound. You're building LC circuit. Where that circuit ends up providing the most choking depends on the diameter of the coil, the spacing of the turns, even the velocity factor of the coax. And it only does that over a very narrow bandwidth. The maximum choking will be over a couple of MHz, it'll do almost no choking 7MHz off centre. Making one from RG213 on a 4.25" core, changing the number of windings from 5 to 7 results in a drop of the frequency for choking of over 7MHz. You cannot trust suggestions for building them from anyone online unless it is from someone like Steve G3TXQ who has built them and measured them with a vector network analyser and even then the chart he produces only works if you build the air wound chokes exactly as stated. A turn more or less or substituting a different coax means there's no guarantees. The only way you can ensure the one you're building is working the most where you want is to build it then measure it with test equipment.

Ferrite chokes. The manufacturers of the ferrites produce data sheets with charts on which show the impedance for a single turn or number of turns of wire at different frequencies.

Looking at the following chart for a Mix31 Fair-Rite one taken directly from their website data for a 2631102002 ferrite....

2631102002.png



We can see from the bottom graph that three turns gives approximately 1600 Ohms choking on the 11m band. It does not matter what coax you're using or what size the loops are through the ferrite, the result will be the same. We can wind that choke with certainty that it will do what it states with any testing done only really verifying the manufacturer spec.
 
Nov 2, 2013
45
5
18
looking at fair rite website ..the quad is a simple 27 500 tuned antenna ..do I want air wound and or just ferrite clamps sir .. a link for what I need would save me a lot of questions ..thanks for you help ..KP160
 

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