It seems convincing. A measurement without an exact definition of the setup is not replicable.
In the meantime, I made some other tests. My R-390A gives a 10 dB S/N with -104 dBm (1.41 uV) signal applied to one half of the balanced antenna input, using the DA-121 (@7,580 kHz). If I use the unbalanced antenna input, which should have a high impedance, I use a 50 ohm terminator for the generator. In this case, I get 107 dBm (1 uV), i.e. a difference of 3 dBm, which I attribute to the insertion loss of the DA-121. Larry said that the correction factor should be 0.55, and I follow him in this, simply calculating the voltage divider in the DA-121 (100 + 125 ohm), so I would expect a difference of 5 dBm (if I am right), but maybe that the unbalanced antenna introduces some other difference. BTW, when I bought my R-390A, the seller gave me also this strange object, which should unbalance the balanced antenna, I suppose with a 50 ohm input. In this case I didn’t add neither the DA-121 nor the 50 ohm terminator; despite this, it requires -101 dBm for the same 10 dB S/N. Not very useful, I would say.
> Il giorno 4 ott 2024, alle ore 16:38, Bob Camp <kb...@n1k.org> ha scritto: > > Hi > > The gotcah here is that we really don’t know what the interface between the > signal generator and radio looked like for these official tests. Despite the > document going into a lot of detail, they did not include a schematic or a > part number. (or at least not one that I could find). There are a *lot* of > ways they might have been doing things ….. > > Bob > >> On Oct 4, 2024, at 10:19 AM, Ing. Giovanni Becattini via R-390 >> <r-390@mailman.qth.net> wrote: >> >> But when we perform the classical sensitivity test with a modulated signal, >> do we get the AM or CW value? >> >> Following the instructions I got a value of -104 dBm, i.e. 1.41 uV. Because >> I used the DA-121, the real value should be even better, far from 5 uV. And >> surely my R-390A is not as good as it could be . >> >> Is my reasoning correct? >> >>> Il giorno 4 ott 2024, alle ore 16:13, Barry <n4...@knology.net> ha scritto: >>> >>> I don’t think of 1uV as “bad” but most of these radios will beat that. >>> >>> Thanks, >>> Barry >>> >>>> On Oct 4, 2024, at 8:55 AM, Ing. Giovanni Becattini via R-390 >>>> <r-390@mailman.qth.net> wrote: >>>> >>>> Wow, thanks! >>>> >>>> By the way, do you know why the sensitivity values were so bad? Are we the >>>> ones who are taking measures that are too lenient or are they the ones who >>>> were too conservative? >>>> >>>> Thanks again >>>> >>>> Gianni >>>> >>>>> Il giorno 4 ott 2024, alle ore 15:37, Larry Haney <larry41...@gmail.com> >>>>> ha scritto: >>>>> >>>>> Hi Gianni and Barry, Tom Marcotte and Al Tirevold (SK) obtained and >>>>> cleaned up the specs for the 390A and put it on our website. Here's the >>>>> link: mil-r-13947b– (r-390a.net) >>>>> <https://www.r-390a.net/mil-r-13947b.pdf>. Unfortunately, the entry in >>>>> References page indicates it is for the R390(), but it is also the the >>>>> 390A. I will be changing that shortly. >>>>> >>>>> Regards, Larry >>>>> >>>>>> On Fri, Oct 4, 2024 at 4:49 AM Ing. Giovanni Becattini via R-390 >>>>>> <r-390@mailman.qth.net <mailto:r-390@mailman.qth.net>> wrote: >>>>>> Have ever been released official specs for the 390A? >>>>>> >>>>>> The manuals report few data and neither too correct, for what I can >>>>>> understand (e.g., sensitivity) >>>>>> >>>>>> Thanks >>>>>> ______________________________________________________________ >>>>>> R-390 mailing list >>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390 >>>>>> Help: http://mailman.qth.net/mmfaq.htm >>>>>> Post: mailto:R-390@mailman.qth.net <mailto:R-390@mailman.qth.net> >>>>>> >>>>>> This list hosted by: http://www.qsl.net <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@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@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@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
