TR: [Elecraft] Rx filter attenuates at 100 Hz bandwidth

Wed Dec 18 12:00:01 2002

Hi from France,

I recently did some experiments on Xtal filters and that is noticed is =
directly linked with the filter design.
Ladder filters show ALL the same effects and, that's sure, the bandpass =
CANNOT be indefinitly narrowed.
As everybody mentionned, a trade-off exists between the bandpass and =
the attenuation.=20

Working on 36 MHz filter (overtone 3), I observe that was possible to =
build a "decent" filter for SSB but the CW version was too lossy.
 Adding a 36 MHz amplifier to restore the initial overall gain, =
dramatically destroys the S/N ratio of the IF channel.

That's my experience.

73
G=E9rard / F6EHJ

> ----------
> De : 	Vic Rosenthal[SMTP:[email protected]]
> Date> =A0> :	mercredi 18 d=E9cembre 2002 17:09
> A :	[email protected]
> Objet :	Re: [Elecraft] Rx filter attenuates  at 100 Hz bandwidth
>=20
> Eric Manning wrote:
> >=20
> > I had exactly the same thing - serious loss of gain with FL4 at 100
> > HZ, so I opened it up to 250 Hz and the problem went away.
>=20
> Me too.  However, I noticed in Spectrogram that the actual width of =
the passband
> wasn't a whole lot narrower when set at 100 than at 220 (which is the =
value I
> finally settled on).  It seems that when you get to a certain point, =
the
> attenuation increases faster than the width decreases.  So there's no =
reason to
> go past that point.  I find that I rarely use even the 220 Hz =
setting, finding
> 400 Hz adequate for heavy QRM situations.
>=20
> I should add that this experience is with the new matched crystal set =
from
> Elecraft.
>=20
> 73
> Vic K2VCO
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>=20