[ARC5] Visual alignment of BC-454

[Dennis Monticelli]

Ken,

Being a relatively high IF, perhaps the gimmick's sheer capacitance pulls
the center freq a bit as it peaks the gain.  This would explain the lump
off to one side of the passband.  A gimmick cap on both IF's set at a value
for moderate regeneration would pull the stages equally while helping build
up sharper shoulders thanks to having two IF cans involved with Q
improvement.  Then the Mixer IF can could be tweaked to line up with the
other two.

Dennis AE6C


On Thu, May 23, 2013 at 1:07 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 23 May 2013 at 9:21, Dennis Monticelli wrote:
>
> > Ken,
> >
> > That is not jitter because it would then be random.  The double trace
> > is an artifact of the triggering for each successive sweep.
>
> That may be so, all right: another explanation is residual hum or audio on
> the
> signal.
>
> >  In any
> > case, the shape of the passband is not in question, that much is
> > clear.
>
> Thanks! At least I got something right. ;-)
>
> >
> > The asymmetry within the passband is what I would expect when only one
> > IF stage undergoes regeneration while the coupled other half does not.
> >  Hard to tell how much overcoupling is going on because of the
> > asymmetrical IF gain of the respective coupled stages.
>
> Yes. In fact, when I reduced the regeneration, the display reverted very
> quickly to the single-hump classic shape, but gain was severely reduced. I
> am thinking of temporarily removing the gimmick-capacitor and then
> sweeping it.
>
> >  I wonder how
> > much better it would look if both IF stages were regenerated?
>
> Hmmmm.....might not be a bad idea to try.
>
> >  Perhaps
> > it would be a prettier passband if less regeneration was applied but
> > it was applied equally within each stage.
>
> I'll bet you're right. I may be able to give that a try soon.
>
> Ken W7EKB
>