Could they have been immersed (more or less) in water then exposed to freezing?
That could have imposed enough stress. Also, as long as the pieces of the beads
themselves remain held together, they will still work just fine. That's why
split beads work, even though they're in two pieces.
Kim Elmore, N5OP
----- Original Message ----
From: Pete Smith <n4zr@contesting.com>
To: Ken Winterling <wa2lbi@frontiernet.net>
Cc: RFI List <rfi@contesting.com>
Sent: Mon, August 23, 2010 9:12:27 AM
Subject: Re: [RFI] Ferrite bead disintegration
They were lying in the grass, largely during the winter months, under no
physical stress at all, unless sun heat might have been a factor due to
the use of black vinyl electrical tape to wrap the beads after they were
put on the RG-59. But this is another reason to be worried about the
bead chokes at my array feedpoints, because they are up year-round,
subjected to whatever stresses are imposed by the wind, weight of the
coax, etc.
73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000
On 8/23/2010 9:29 AM, Ken Winterling wrote:
> Pete,
>
> I have seen mechanical stress do this. You didn't indicate the
> physical construction technique used to build the choke but it is
> possible that movement of the beads against one another caused them to
> crack.
>
> Ken, WA2LBI
>
>
> On Mon, Aug 23, 2010 at 09:10, Pete Smith <n4zr@contesting.com
> <mailto:n4zr@contesting.com>> wrote:
>
> I took apart a home-made 100 bead receiving-only common mode choke
> yesterday. As I peeled off the electrical tape I was surprised when
> each bead that came out of the wrapping disintegrated into dozens of
> fragments. I think I saved about 5 beads out of a 100-bead choke.
>
> What could have caused this? The choke was used over 300 feet
> away from
> my transmit antennas, and never used for transmitting. Morte to the
> point, can I expect to see the same thing in the feedpoint chokes
> of my
> 80m 4-dipole lazy vee array, which have been up and in use for ~10
> years?
>
> --
> 73, Pete N4ZR
>
>
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