[Amps] Rf choke

[R.Measures]

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