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

[Larry Haney]

Barry, if you're not sure, just make the adapter for the 390.  It will work
fine on the 390A.

Regards, Larry

On Mon, Nov 4, 2024 at 9:40 AM Barry <n4buq at knology.net> wrote:

> Larry,
>
> I currently have just the one R-390/URR.  Not sure if I'll ever venture
> again into another R-390 of either version.  I do enjoy them and the
> R-390A/URR is definitely easier to work on so who knows.  I might get fancy
> (or, more correctly, OCD) and put a switch in the box with all four
> resistors...
>
> Thanks,
> Barry - N4BUQ
>
> > 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
> >> >> ______________________________________________________________
> >> >> 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
>