[TowerTalk] [RFI] Snap-on Ferrites

Tue Jun 20 12:19:51 EDT 2017

I have snap on chokes on several devices (TV, Computers, Monitors, etc...) and they work exceptionally well- But what I find works best is keeping RF off of the feedlines. One product that has eliminated  all of the RFI from my 30M dipole off of my roof tower is the Wire Man is my W2DU 1:1 JMP Balun (part #8233, $29.95) ) It is a 3 foot balun of coax fitted with beads- I had to seal it from moisture over what their factory did but I'm telling you, in my case, most RFI on devices comes off of your feedlines going from the antenna back to the shack- I don't run QRO so I can't speak for receiver overload- but with a 100 watts or less, a combination of good baluns and snap on chokes have eliminated all RFI in our household on a small lot- also, we have a common ground using our utility box ground for everything we use...antennas, radios, etc.......and all ground rods at various antennas are bonded to this common ground-

73

Paul  N0AH

________________________________
From: TowerTalk <towertalk-bounces at contesting.com> on behalf of kc4pe <kc4pe at bellsouth.net>
Sent: Monday, June 19, 2017 10:17 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] [RFI] Snap-on Ferrites

On 6/19/2017 10:11 AM, Chris wrote:
>
>> Chris:
>>
>> Clarify: When your talking about turn in a snap 0n your referring to the large snap, 1.75 X 2.25 with a .75 opening, not the 1.255 X .75 with a .312 (5/16_ opening..?
> A turn = winding the wire/cable through and around the core, has nothing to do with size.
/*No what I meant, if your going to add ferrite say on a microphone
line: then using a single pass-thru will not work at
  HF frequencys, you must have ferrite large enough to wrap 3-5 turns
before it will work..???*/

So inquiring minds wonder when you buy a printer/TV set, etc and there is a molded Ferrite block on the AC line. what are they trying to block..??

Ask the manufacturer.  I have no idea what mix they are using or what their target choking frequency is.  But I doubt they are thinking of hams and trying to block HF!
  /*Tryed that ..but don't speak the language...*/

>> So when the Ham says .."Hey I got rid of my RFI on my TX signal by clipping on three blocks of ferrite...
Too vague....
/*Say he put it on the line between the mike and radio...or on his rotor
wire...*/

>> And what about the Ham at the show that was selling  ferrite snap ons (small) with a blue and red labels with bold arrows printed on the black label? What coulkd the arrow mean??
No idea what or who you are referring to, can't comment. If there is no
manufacturer listed with the mix, it is impossible to tell what you've got.
/*Right it was strange, but he had documentation that it was Mix 31
...had single pass through with 1/4 - 5/16 pass ....Some had a red
label, some had a blue label, but all had a very bold black arrow ..
*//*Why would you ever orientate a block of ferrite?

  Thanks Again..*/
>> -Bill .. KC4PE
>>
>>
>> On 6/18/2017 11:11 PM, EZ Rhino wrote:
>>> I think what he (the author) means is this:
>>>
>>>   A snap-on, without multiple turns through around it, isn't effective at HF frequencies.  We're talking about mix 31 or 43 here.  If you wind multiple turns around the snap-on (assuming you pick a size large enough to do so for the cable you're trying to choke) then the choking frequency goes down (to HF range) and the impedance goes up, which is what you want.  So it's not the snap-on that is the problem, it is how you are using it.  If there was such a thing as mix 73 snap-on that was large enough, then that would work as a string of beads choke (because it is effective at HF).  But it would take a lot of them, say 50, to get the proper amount of choking impedance.  A single snap-on just don't have enough umph.
>>>
>>> Hopefully I worded this technically correct.
>>>
>>> Chris
>>> KF7P
>>>
>>>
>>> On Jun 18, 2017, at 20:44 , <john at kk9a.com> wrote:
>>>
>>> I was reading the recent QST article RF Mayhem by WB8IMY. The author said to
>>> avoid using snap-on ferrites for problems caused by HF signals as they
>>> rarely work well at HF. It is best to stick with circular cores.
>>>
>>> Is this correct?  I was not aware that snap-ons were less effective.
>>>
>>> John KK9A
>>>
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