[R-390] R-390/URR Antenna Trimmer Position

[Barry Scott]

I think that's how I understand it now as well.  In that case, my knob is
90 degrees out of position and I think that may make sense based on the way
it peaks.

Thanks,
Barry - N4BUQ


On Sun, Sep 22, 2024 at 8:58 PM Jacques Fortin <jacques.f at videotron.ca>
wrote:

> Don, If I am following everything right, it means that the ANT. TRIM knob
> line have to be inline with the red dot.
> I agree: that’s how my own R-390/URR is settled.
>
> Take care,
>
> 73, Jacques, VE2JFE in Montreal
>
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
> part de Don Heywood
> Envoyé : 22 septembre 2024 17:16
> À : Barry Scott <72volkswagon at gmail.com>
> Cc : Jacques Fortin <jacques.f at videotron.ca>; R-390 Mailing List <
> r-390 at mailman.qth.net>
> Objet : Re: [R-390] R-390/URR Antenna Trimmer Position
>
> Barry, I'm home from the hospital now and I've got it straight. On the
> tech manual page that shows the alignment for the RF deck it says set the
> antenna trim to zero. I have penciled in zero equals red dot up.
> That 3 o'clock position makes it easy to see the dot when the RF deck is
> out.
> So, red dot up at zero on the dial, and the alignments are done in this
> position Sorry for the confusion, must've been the anesthesia Don WC4G Sent
> from my iPhone
>
> > On Sep 22, 2024, at 15:14, Barry Scott <72volkswagon at gmail.com> wrote:
> >
> > Another list member, Don Heywood, let me know that, like the R-390A,
> > the shaft on the R-390 also has a red dot which is used to align the
> > capacitor.  It's also mentioned in the Pearls document.
> >
> > With the dot pointing to the 3:00 position, the knob should point to
> > the
> > 12:00 position.  I just looked and, indeed, that dot is on mine (and
> > somehow, I had the knob pointing to almost exactly where it should be
> > pointing).
> >
> > I still don't know where that's described in the manual but apparently
> > it's there somewhere.
> >
> > Thanks,
> > Barry - N4BUQ
> >
> >
> >> On Sun, Sep 22, 2024 at 9:50 AM Jacques Fortin
> >> <jacques.f at videotron.ca>
> >> wrote:
> >>
> >> Hi Barry,
> >>
> >> Well... the problem will arise when you will try to align the Antenna
> >> circuit RF transformers...
> >> During that operation, the ANT TRIM position is specified to be a "0"
> (ANT.
> >> TRIM caps meshed halfway).
> >> I vaguely remember that -4 position relates to fully meshed ANT. TRIM
> >> caps and that I had "marked" the related shaft position when I worked
> on mine.
> >> But trying to determine the caps position when the whole RF deck is
> >> in place is... well.. not that easy.
> >>
> >> I have an idea, but it will require the use of a handheld capacitance
> >> meter, plus the removal of T201...
> >> The logic behind is that both sections of the ANT. TRIM cap are
> >> connected to
> >> T201 pin 5 when the MC control is at 00.
> >> With the T201 out of the way, a capacitance meter can be connected to
> >> the
> >> T201 socket between pins 4 and 5 and the measured capacitance value
> >> looked at when the shaft is rotated.
> >> There should be a maximum and a minimum capacitance value measured.
> >> When the value is maximum, the caps are fully meshed and that is the
> "-4"
> >> position of the control.
> >>
> >> I never tried to do it that way.
> >> So I do not know if that make sense overall... or not !
> >>
> >> 73, Jacques, VE2JFE in Montreal
> >>
> >>
> >> While I had the RF Deck out to work on the gear train, I rotated the
> >> Antenna Trimmer and left it at some unknown rotational position when
> >> I installed the RF Deck back into the cabinet.
> >> I'm now trying to determine the rotational position of the Antenna
> >> Trimmer's shaft and where that position should be located with
> >> respect to the markings on the front panel.
> >> I realize the trimmer can just be rotated to where the signal is best
> >> and the numbers may not really have much meaning but I'd think that
> >> some position (say, 12:00) should correspond to a given mesh value of
> >> the cap's plates (e.g. when the knob is at -4, the plates should be
> >> fully meshed, etc.).
> >> The only reference to that that I've found are the paragraphs that
> >> deal with the removal and installation of the front panel.  The
> >> manual states to position the knob at the -4 position before removing
> >> the front panel and then, when replacing the front panel, replace the
> >> knob (presumably at the
> >> -4 position).  That's fine but if the Antenna Trimmer is rotated
> >> while the front panel is removed, then it isn't clear to me how to
> >> replace the knob properly w.r.t. to the capacitor's plates.
> >> Anyone know?
> >> Thanks,
> >> Barry - N4BUQ
> >>
> >>
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net Please help support this email
> > list: http://www.qsl.net/donate.html
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>