On Nov 21, 2005, at 4:45 PM, k7fm wrote:
> It has been stated that winding two solenoids rf chokes end-to-end
> will in effect make one rf choke, so that they must be at right
> angles.
>
> That statement is only true if the rf chokes couple. But, it is
> possible for them not to couple. How? Wind them in opposite
> directions. Then, coupling will be minimal.
>
> I just wound two solenoid rf chokes in line, separated by about 1/4".
> Measured the resonance of the first rf choke before winding the
> second. Then, wound the second with more turns, so I could look for a
> different resonant frequency. The resonant frequency of the first was
> unaffected by the additional solenoid wound end-to-end. Then checked
> the resonant frequency of the second coil. It was right where it was
> supposed to be.
>
> I then measured the inductance and they added.
This is true if there is a considerable distance between the two
inductors.
>
> So, it is possible to make rf chokes on one form for the purpose of
> avoiding resonant frequencies.
With a gap that is > 4x the coil diameter, assuredly.
>
> The problem with resonant rf chokes is that the hi Q creates
> fireworks. There may be another solution, and that is to use
> resistance wire for the rf choke.
The Collins ART-13 did this.
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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