>
>Someone said:
>
>> The highest L choke that has no resonances below 30MHz is c. 65uH.
>>
>
>That isn't true.
>
Yet another pontification. The smaller choke in the 8169 amp photo on
my Web site has 65uH. It is resonant c. 30MHz..
>The resonant frequency varies greatly with capacitance, and how
>that capacitance is distributed.
By measuring choke resonances with a dipmeter, I found that distributed C
varies little whether or not one leaves gaps in the windings. The radio
guru in Newington who came up with this discovery should have checked it
out with a dipmeter on both types of chokes. . .
> Even what the choke is around
>changes the resonant frequency.
>
>Physically small chokes have much higher series resonant
>frequencies than larger chokes, even when the inductance is the
>same.
>
>Stray capacitance at the middle of the choke is the problem at the
>first resonant frequency, so removing turns there and making an air
>gap will shift the first series resonant frequency higher.
>
apparently not very much. End to end coils of wire couple so closely
that they act pretty much like one large coil. . Splitting the choke
into two sections and mounting them at right angles is what works. (see
8169 amp photos)
>
cheers
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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