----- Original Message -----
Sent: Tuesday, May 19, 2009 11:07
PM
Subject: Re: LF: 518khz - Notch
Filter.
Ansoft Designer came up with this solution.
The component values aren't particulalrly nice, and there is
almost certainly a nicer design with transformers to be found, but...
Andy G4JNT
2009/5/19 Rik Strobbe
<[email protected]>
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.
