[ARC5] Selectivity improvement in ARC-5 receivers.

[Dennis Monticelli]

The ultimate stop band is easy to determine.  You simply count the number
of L's and C's and factor in their respective series and shunt positions.
 Once you are far from resonance the effect of Q disappears and you left
with 6dB/octave per reactive element (i.e. just their lumped reactance).
 This of course assumes no stray paths not shown on schematic such as stray
capacitive or magnetic coupling due to a poor layout.  The lower the IF
freq, the less the strays matter.

Dennis AE6C


On Sun, Jun 1, 2014 at 2:03 PM, Kenneth G. Gordon <kgordon2006 at frontier.com>
wrote:

> This month's Electric Radio Magazine has Jeep Platt's article on the
> subject
> above in it. Jeep's article is very well written and very useful.
>
> However, I have had a question concerning ultimate stop-band selectivity
> for
> some time now after a discussion with another of our list-members during
> our
> discussion on Jeep's final method.
>
> It is my understanding that the ultimate stop-band selectivity is
> determined
> NOT by any physical characteristic of the IF transformers, but, rather, by
> the
> IF frequency itself.
>
> I.e., at the 60 db down point, the true selectivity is determined more by
> the IF
> frequency than the separation of the two IF coils.
>
> I vaguely remember from my EE course in filters that it was "so many db per
> octave", or something similar.
>
> Can anyone here tell us what I am even talking about here, and fill in the
> details?
>
> I'm at a loss, but still very confused.
>
> Kenneth G. Gordon W7EKB
>
> "Courage is being scared to death but saddling up anyway."--- John   Wayne
>
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