On Fri,9/11/2015 3:17 PM, Richard (Rick) Karlquist wrote:
On 9/11/2015 1:24 PM, Jim Brown wrote:
Which is a terrible choke, because the Q of #61 material is far too
high.
73, Jim K9YC
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There is a tradeoff regarding power handling. 61 material will have
far less heating than, for example, 43, or 31. Depending on what
you are trying to do, 61 might make sense. I use it in my
50 ohm to 450 ohm bal-bal transformer.
You're talking about a TRANSFORMER to handle RF power, where higher Q is
desirable. My comment was on use of the core for a choke.
Important fundamental principle: Chokes want LOW Q material, lots of
resistance, transformers want HIGH Q if they need to handle power. #61
high Q below 10 MHz, low Q at UHF, so it is a good choke material at
UHF, a good transformer material below 30 MHz. This is true of nearly
all ferrite materials -- materials have low loss at lower frequencies,
so can handle power, much more loss at higher frequencies, so can't
handle power but are good as chokes. A key difference between materials
is WHERE they transition from low loss to high loss.
73, Jim K9YC
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