[R-390] DA-121 and R390/URR

[Larry Haney]

Barry,  I'd say that if you are going to work more on As, then do the
da-121.

Regards, Larry

On Mon, Nov 4, 2024 at 6:36 AM Barry Scott <72volkswagon at gmail.com> wrote:

> Okay, I agree.  I think as long as one can get a signal into the RF
> deck, it can be used to align the coils and trimmers as necessary.
>
> I'm going to make a matching network and wondered if there was any
> really good reason to use 68 and 100 ohm resistors or 95 and 75 ohm
> resistors.  Probably doesn't matter...
>
> Thanks,
> Barry - N4BUQ
>
> On Mon, Nov 4, 2024 at 12:52 AM Larry Haney <larry41gm2 at gmail.com> wrote:
> >
> > Hi Barry,  Yes, the DA-121 is what's recommended for the 390A when doing
> alignment, but it does not make any difference if you use the adapter or
> not for that, but it should be used for sensitivity and SNR measurements.
> At least, that's been my experience.
> >
> > I believe that the balanced antenna coils are a little different on the
> 390, but the DA-121 should be close enough to work correctly for it.  But,
> there again, I doubt that an adapter is necessary for alignment on the 390,
> either.  It should be used for sensitivity and SNR measurements though.
> >
> > Regards, Larry
> >
> >
> > On Sun, Nov 3, 2024 at 6:04 PM Barry Scott <72volkswagon at gmail.com>
> wrote:
> >>
> >> In the last few weeks, there were several posts regarding using the
> >> DA-121 to determine sensitivity for, presumably, an R-390A/URR.  The
> >> DA-121 uses a 68-ohm in parallel and a 100-ohm in series with the
> >> signal generator's output.  Is this the recommended adapter also to be
> >> used for the RF alignment of the R-390A/URR when using the balanced
> >> input?
> >>
> >> I ask because the R-390/URR manuals say to use a 75-ohm parallel
> >> resistor with a 95-ohm series resistor when performing the RF
> >> alignment.  I realize there's not enough difference between those two
> >> networks to matter that much but I am curious as to why the two values
> >> are different between the models.  Are the RF transformers slightly
> >> different between them?
> >>
> >> Just curious.
> >>
> >> Thanks,
> >> Barry - N4BUQ
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