Gary,
a simple series L-C notch works best when
- Q is high = you need a good coil (capacitor Q shouldn't be the problem)
- the output "sees" a high impedance (FET buffer)
- the source impedance is high compared to the loss resistance of the
coil (eventualy put a R of a few 100 Ohm in serie with the antenna)
But it will be a hard job to get a decent attenuation at 518 while
passing 501-506 without too much losses.
An alternative would be a xtal filter as a passband filter for 501-506.
If you can find a number of 500kHz xtals and "polish" them up some kHz.
73, Rik ON7YD - OR7T
Quoting Gary - G4WGT <[email protected]>:
Hi LF,
You may have seen an image of a NAVTEX signal on my 500KHz grabber at about
506KHz. The original of this image is at 518KHz. The receiver for this
grabber is a Softrock Lite 455KHz module modified for 500KHz.
I have attempted to notch the signal using a simple series or parallel
filter but only succeeded in seriously degrading the whole band possibly due
to the bandwidth of the filter??
Is there some simple narrow notch filter which I could use to remove the
offending signal.
73,
Gary - G4WGT - IO83QP.
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