Is it possible that without the front tuned circuits there is more noise and thus the S/N ratio is worse?
From my side, the unbalanced antenna (with the DA-124) gave worse results. In this case, however, I did not applied any correction factor (like for the DA-121) because I thought the DA-124 on a high impedance had little loss. Is it correct? > Il giorno 13 ott 2024, alle ore 23:21, Bob Camp <kb...@n1k.org> ha scritto: > > Hi > > When they are measuring “AM Sensitivity” are they running 30% modulation or > 100%? > > If by some chance, they are running 30% and you are running 100% …. the > numbers will off a bit. Will it be 3:1? Probably not. Still it’s going to > impact things quite a bit. > > I’d doubt they switched techniques between the two plots. Switching them > between a 1953 document and one from 1961 …. yup, could indeed happen. > > Bob > >> On Oct 13, 2024, at 5:12 PM, Jacques Fortin <jacque...@videotron.ca> wrote: >> >> The chart TM 856-91 attached. >> >> 73, Jacques, VE2JFE in Montreal >> >> -----Message d'origine----- >> De : r-390-boun...@mailman.qth.net <r-390-boun...@mailman.qth.net> De la >> part de Jacques Fortin >> Envoyé : 13 octobre 2024 16:13 >> À : 'Larry Haney' <larry41...@gmail.com>; 'Jim Whartenby' <old_ra...@aol.com> >> Cc : r-390@mailman.qth.net >> Objet : Re: [R-390] Official specs >> Importance : Haute >> >> Well... >> I found two diverging statements.... >> In the first R-390/URR manual (Collins Radio, 23 October 1953) the Figure 95 >> on page 172 (Also IDed TM 856-91) shows that the sensitivity is higher for >> the Unbalanced input, compared to the Balanced one. >> This is the only manual I know that gives a "sensitivity" plot for the >> R-390/URR. >> On the R-390A/URR side, the TM 11-856A, on pages 173 and 174, seems to tell >> us the reverse from the charts M and J (More sensitivity on the balanced >> antenna input than on the unbalanced one) I do not exclude the possibility >> that one of those "sources" could tell the truth in reverse.... >> >> Bottom line: we have to test ! (once again). >> >> 73, Jacques, VE2JFE in Montreal >> >> Hi Jim, My thinking in why the second 'balanced' entry is actually the >> Unbalanced info is that the Unbalanced antenna input is the high impedance >> input and therefore would have the higher microvolt readings. And in the >> numerous other places in the spec where both are listed, the 'balanced' one >> is first. >> >> Regards, Larry >> >> On Sun, Oct 13, 2024 at 8:27 AM Jim Whartenby via R-390 < >> r-390@mailman.qth.net> wrote: >> >>> I agree that one list is mislabeled but I would think that the first >>> "Balanced" list is the one that is actually the Unbalanced spec. >>> >>> My reasoning is that the CW input voltage spec is lower in the first >>> list and higher in the second for all frequencies. We may disagree on >>> the actual insertion loss of the DA-121 but it would still be higher >>> for all frequencies then the DA-124 which uses a series capacitor to >>> mimic a short antenna instead of a voltage divider to transform impedance. >>> >>> Jim >>> >>> Logic: Method used to arrive at the wrong conclusion, with confidence. >>> Murphy >>> >> >> ______________________________________________________________ >> 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-URR_Collins_1953_p172.pdf>______________________________________________________________ >> 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
