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Ferrite question

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jnojr

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I bought a couple of KB9VBR GMRS J-pole antennas. The instructions say to create a balun out of a few loops of cable, but that ain't happenin' with LMR400. The option given is to use ferrites. I bought a package of 11mm snap-on ferrites, but they're a little loose. I can't easily find 10mm ones. Can I use some electric tape to snug them up? Or anything else I should be considering?

Also, how do I know what's the right number of ferrites to add?
 

prcguy

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I bought a couple of KB9VBR GMRS J-pole antennas. The instructions say to create a balun out of a few loops of cable, but that ain't happenin' with LMR400. The option given is to use ferrites. I bought a package of 11mm snap-on ferrites, but they're a little loose. I can't easily find 10mm ones. Can I use some electric tape to snug them up? Or anything else I should be considering?

Also, how do I know what's the right number of ferrites to add?
For VHF and UHF I've found three 43 mix or Laird 28 mix snap on ferrite to be effective. I had a serious LED light RFI problem and started with one snap on which did nothing, then two which made a slight improvement then three in series which really worked well. If the snap on is a little loose you can use a ty-rap on each side of the string to keep them in place but be careful not to squeeze or deform the coax.
 

K6GBW

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Ferrites can bite if they get scared.


Kidding...honestly, you probably don't need ferrites on UHF frequencies to begin with. Just leave them off and see if there's any noise. If there isn't, then don't bother.
 
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