[R-390] Staggertuned IF Question

[kirklandb at sympatico.ca]

CAPs generally change the resonant point not the Q of the circuit. Q is a measure of the energy loss in the tuned circuit.  As you load a parallel (or series) tuned circuit down, you lower the Q. For parallel tuned circuits, decreasing the parallel resistance lowers the Q.

The Q of a parallel tuned circuit is affected by both the Q of the inductor and the capacitor. Generally the Q of the inductor dominates  - inpart due to the resistance of the wires.

bk

> 
> From: "Cecil Acuff" <chacuff at cableone.net>
> Date: 2006/09/14 Thu AM 11:46:45 EST
> To: <n4buq at knology.net>,  <R-390 at mailman.qth.net>
> Subject: Re: [R-390] Staggertuned IF Question
> 
> I'm working from memory here so YMMV....(your memory may vary)
> 
> My thoughts are NO.  As I remember there is a capacitor involved on each can 
> that sets the Q for the coil...I can't remember if the cap needs to be there 
> when you are to stagger tune or vice versa....
> 
> Seems the cap reduces the Q allowing a smooth bandpass when stagger tuned 
> where without the cap it's too peaky....
> 
> Roger you will have to fill in the blanks on my memory cell issue on this 
> one...
> 
> I know the R-390/URR is straight tuned but I've heard the "A's" are 
> split...some setup for stagger tuning, some not.  I've heard also of folks 
> cutting out the caps and straight tuning but I'm not sure there are not 
> stage gain problems with doing that...
> 
> Good subject though...
> 
> Cecil...
> ----- Original Message ----- 
> From: <n4buq at knology.net>
> To: <R-390 at mailman.qth.net>
> Sent: Thursday, September 14, 2006 9:03 AM
> Subject: [R-390] Staggertuned IF Question
> 
> 
> > Are all IF modules capable of stagger-tuning?  I started trying this with
> > my current project with no results.  The IF won't even think about hearing
> > a 467kc signal.  I was able to do this on my Motorola, but not this one.
> >
> > I seem to recall reading where not all IF modules were designed to
> > accomodate stagger-tuning.  Is this true?  If not, then I suppose I have
> > more work to do.  If so, then do I assume I peak all the slugs for 455kc?
> >
> > Thanks,
> >
> > Barry - N4BUQ
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> 
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