[R-390] 0.5-8.0 Low Sensitivity (Long)

[JMILLER1706 at cfl.rr.com]

The sllugs have different permeability depending on what circuit they 
are used in, i.e. it is possible a slug from an RF coil will not 
perform the same as a slug in the IF.  If you interchanged slugs 
accidentally this might cause mistracking.

----- Original Message -----
From: Cecil Acuff <chacuff at cableone.net>
Date: Monday, September 11, 2006 11:15 am
Subject: Re: [R-390] 0.5-8.0 Low Sensitivity (Long)
To: ToddRoberts2001 at aol.com, r-390 at mailman.qth.net

> Well that's another tip off that there is a resonance problem in 
> that 
> particular tuned circuit.  The slug tuning should never be at it's 
> threaded 
> limit to achieve the peak....(it's actually not the peak because 
> you are at 
> a physical limit prior to reaching the peak)
> 
> I've had to add and sometimes even remove fixed capacitance to get 
> within 
> the range of the trimmer.  It's seems to me the inductance value 
> has changed 
> from when the can was manufactured.  Maybe there is fine particles 
> of slug 
> material worn into the coil form.  Maybe the slug has a chunk 
> missing off 
> the bottom of it...who knows.  The factory value of the fixed mica 
> cap is no 
> longer correct and requires custom matching to the current circuit 
> conditions.  I've had to do it several times and sometimes the 
> effect on 
> performance is dramatic because you don't know how far off of the 
> real peak 
> you are until you can achieve two distinct peaks with the trimmer 
> capacitor 
> at different positions in their rotational range.  It's worth the 
> effort....
> Cecil...
> ----- Original Message ----- 
> From: <ToddRoberts2001 at aol.com>
> To: <r-390 at mailman.qth.net>
> Sent: Monday, September 11, 2006 9:59 AM
> Subject: Re: [R-390] 0.5-8.0 Low Sensitivity (Long)
> 
> 
> >
> > All else works fine now and I'm tempted to just leave well 
> enough alone.
> > However, I'm
> > puzzled why fresh trimmers and new micas at spec values cannot 
> get two 
> > peaks
> > during
> > alignment.
> >
> > Got any ideas?
> >
> > Dan
> > WB4GRA
> >
> > Have you tried screwing in the slugs a few more turns? What 
> happens when 
> > you
> > screw in the slugs a few more turns? Does the signal continue to 
> peak or 
> > does
> > it start to fall off? If it starts to fall off then the single 
> peak would
> > appear to be near correct even though you only get one peak when 
> the slug 
> > is
> > maxxed out. I wouldn't worry too much about a single peak if the 
> > sensitivity is
> > back to normal. 73 Todd WD4NGG
> > _____________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/faq.htm
> > Post: mailto:R-390 at mailman.qth.net
> > Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> > 
> 
> 
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>