I guess I'm using the term "beads" a bit figuratively taking into
account toroids big enough to pass a coax connector on RG-213. For HF
choking they need an initial permeability of a few hundred to 1200 or
so. For a transformer that permeability for HF would be 50 or 125. Its
really hard to put multiple turns of RG-213 through any size of toroid.
Yes on the basis of the least cost of ferrite, a chunk of teflon coax
winds on ONE large toroid to make a decent choke, but that teflon coax
gets warm at 1200 watts or more.
Snap on RFI toroids are in the same region of sizes, but the potential
for a lowered effective permeability due to the airgap at assembly is a
significant problem.
73, Jerry, K0CQ
On 8/6/2010 1:15 PM, Jim Brown K9YC wrote:
On Fri, 06 Aug 2010 12:43:30 -0500, Dr. Gerald N. Johnson wrote:
That depends a great deal on the ferrite mix. There are beads suitable
for HF
The only beads I know of that are suitable for HF are the tiny beads that
W2DU found 30 years ago for his chokes. They only fit miniature coax, and
it takes HUNDREDS of them to make a choke that still doesn't work as well
as the multi-turn I've described. Those made with fewer beads are less
effective AND they can be blown up with high power.
73, Jim Brown K9YC
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