[R-390] RF deck update

[Jacques Fortin]

Hi Russ,

May I suggest to check if your Z213s tuning slugs are the right ones ??
The RF slugs (Z201 to Z206) are brownish-gray and have a relative
permeability of 10 (which is normal for a maximum tuning ratio of 3:1 and ~
2:1 is used in the R390-A).
The IF slugs (Z213 and 216) are slate grey, or slightly greenish (depending
on origin) and have a relative permeability of 4 (normal for a maximum
tuning ratio of 2:1 and ~ 1.5:1 is used in the R390-A).
I had a Moto 56 RF deck with mixed slugs between RF and IFs, and also slugs
bronze in color that measured 7.3 of relative permeability (no good at all
for a R390-A).
Mixing of the slugs can give the type of problems you are experiencing....
so it's worth to check that.
Measuring the relative permeability of the slugs was easy for me because I
have an impedance analyser.
I just wound 20 turns of 24 AWG around the slug(s) and measured the
resultant inductance.
Then by carefully removing the slug, keeping the winding "free standing", I
measured the resultant inductance again.
The ratio between the two measurements is the relative permeability of the
slug.
Some could also use a capacitor in parallel with the winding and a grid dip
meter to check the resultant frequencies.

Let us know

73, Jacques, VE2JFE

-----Message d'origine-----
De : R-390 [mailto:r-390-bounces at mailman.qth.net] De la part de
wb3fau55 at neo.rr.com
Envoyé : 10 août 2016 04:58
À : r-390 at mailman.qth.net
Objet : [R-390] RF deck update

Larry and others-
  So  I went back to RF alignment on  lower  bands.  I did  get the 1 to 2mc
rack peaked up and receiving the strong local signals.  Sensitivity is low
but they are there!
  Going then to Z213-  the 2nd one  shows  no peaking.  I tried 2 different
cans  from other receivers,  but no change.  So I see a cap  right at the
terminals of the can,  I should be able to  measure that....Russ.
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