Tom Rauch wrote:
>
> See how simple the design is? ....and it doesn't modify the
> impedance of the system very much.
>
> The limitations are the Q of the tuning capacitor and
> (mostly) Q of the inductors. With better inductors it would
> an almost perfect filter. The cost and size prohibits using
> really good inductors.
Two other important limitations:
1. Only one BC frequency can be nulled out. If you have multiple strong
signals, you are still out of luck.
2. It will perform poorly for 1700 kHz BC stations. I have a
nice strong one at my QTH. You might like to measure below
1800 kHz for diagnostic purposes, even though that is out of band.
This trap would be lucky to get you down to 1800.
Not sure why the Q should be limited by cost and size. You can get a Q
of 400 with an inductor wound on a 3/8 inch, 50 cent low-permeability
ferrite toroid.
Rick N6RK
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