Hi Bob, Thanks for the interesting links. By means of them, I could discover that the model 80 is the civil version of my TS-497 which I bought almost for free because nobody wants it. It has wonderful mechanics and a very good attenuator which arrives down to 0.1uV.
> Il giorno 5 ott 2024, alle ore 17:00, Bob Camp <kb...@n1k.org> ha scritto: > > Hi > > I’m quite sure the engineers involved understood this and that. The gotcha is > that these spec’s are written by a committee. Having sat for un-ending > amounts of time on some of those committee’s, what gets said is not always > what goes in the spec. This or that gets shoved off to some other process or > document ( or maybe simply ignored). Often the “shoved off” stuff turns into > informal notes that somebody using the spec very much needs to have handy. > Welcome to why you spend all those hours sitting there …. :) :) > > While that app note is a fun read, it turns out that it’s not the full story. > These generators do not always have a 50 ohm output impedance. Put a VNA on > one and crank the attenuator …. not always 50 ohms. > > If you take a look at this manual from 1945 (for the 80, a cousin of the 82): > > http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Boonton/Boonton_Model_80_Manual.pdf > > It includes an “optional 6 db pad”. Why? The output impedance was a bit wonky > (even for that era) without it. > > The model 82 (and its cousins the 80 and 84) came out in the while WWII was > still going on. They stayed in production for quite a while after that: > > https://www.worldradiohistory.com/Archive-Catalogs/Miscellaneous-Manufacturers/Laboratory-Standards-1949-Catalog.pdf > > It’s a generator that “covers the frequency range”. (it’s the only one in > that catalog that does so). An equivalent would be another generator that > covers the frequency range. > > By the 1960’s most outfits had moved on from WWII test gear (if the spec > allowed them to do so). > > So: > > *Is* this a reason the sensitivity specs are a bit crazy? We simply don’t > know. We *do* know that they are more than a bit off from what every example > of the radio any of us have seen actually does. Given how tight the rest of > the specs’s are, That’s pretty strange. > > *Could* it be the reason? …. it just might be. You certainly can confusion > about that 6 db pad on the model 80 popping up in a lot of places. > > Bob > >> On Oct 4, 2024, at 11:13 PM, Jim Whartenby via R-390 <r-390@mailman.qth.net> >> wrote: >> >> BobI don't know why you are speculating "Since you can use any signal >> generator" when MIL-R-13947B(SigC) on page 20 specifies the Measurements >> Corp Model 82 signal Generator, or it's equal. Your concern with matched >> impedances between the generator and the R-390 may appear to be valid but >> this seems to have been accounted for in the R-390 spec with higher input >> voltages to account for the mismatch losses. Collins and the Signal Corps >> specified the 125 ohm input impedance of the R-390 and they were surely >> aware that the standard impedance of high end signal generators was normally >> 50 ohms. >> >> Check out http://hparchive.com/Boonton/BRC-The-Notebook-03.pdf which is a >> 1954 Boonton Radio explanation for the use of Dummy Antennas. Everything >> you need is in the first four pages. It explains why the mismatch between >> 50 ohms and the receiver input impedance reduces the loading on the receiver >> input tuned circuits and recovers the Q of the receiver RF input tuned >> circuits. This also affects favorably the S+N/N measurement. There is a >> reason for the apparent madness. >> Jim >> >> Logic: Method used to arrive at the wrong conclusion, with confidence. >> Murphy >> >> On Friday, October 4, 2024 at 07:23:24 PM CDT, Bob Camp <kb...@n1k.org> >> wrote: >> >> Hi >> >> Based on a *lot* of interaction with DOD source inspectors over the years … >> it’s very much a “that depends” sort of thing. The guy you get this month >> may be *very* different than than the guy who comes in next month. >> >> Since you can use any signal generator, there is room for “trouble” with >> minimal specs. Typically the way this works out is a request to clarify >> things. Unfortunately that stuff does not get into the official specs. Yes, >> some of us have pointed that out as a problem …. never got addressed AFIK. >> >> Bob >> >> >>> On Oct 4, 2024, at 5:19 PM, Jim Whartenby via R-390 <r-390@mailman.qth.net> >>> wrote: >>> >>> Bob >>> You are over thinking the testing. The generator is terminated but not in >>> it's characteristic impedance. Collins and the agency letting the contract >>> agreed on a test method and wrote it down in the test procedure. Anything >>> that would affect the testing like VSWR has already been considered and >>> accounted for. That Hams don't use the proper termination for the signal >>> generator, according to the spec, which affects the perceived sensitivity >>> is another issue. Spec is spec as they say. >>> >>> Not all Government Source Inspectors are knowable about the equipment that >>> they are reviewing and putting their inspection stamp on. Not all Signal >>> Corps equipment is inspected by Army GSIs. Every once in a while, Army >>> equipment will have an anchor stamp on it and vice-versa. Sometimes >>> certain specs are wavered if not considered critical, most often they are >>> not. Again, spec is spec. >>> Regards, >>> Jim >>> >>> Logic: Method used to arrive at the wrong conclusion, with confidence. >>> Murphy >>> >>> On Friday, October 4, 2024 at 02:43:36 PM CDT, Bob Camp <kb...@n1k.org> >>> wrote: >>> >>> Hi >>> >>> Ok …. but ….. >>> >>> If it is simply a resistor, then the generator is unterminated. It’s >>> designed and calibrated to run into a 50 ohm load. If all that’s there is a >>> series resistor the generator is not properly set up (and thus not >>> calibrated ….). Yes some generators deal with this better than others. >>> >>> My guess is that there’s more to the load circuit than just that resistor. >>> Without a schematic …. who knows …. >>> >>> Bob >>> >>> >>>> On Oct 4, 2024, at 12:53 PM, Jim Whartenby via R-390 >>>> <r-390@mailman.qth.net> wrote: >>>> >>>> Bob >>>> But we do know what the interface is between the signal generator and >>>> antenna input. On document page 20, the balanced RF input is in series >>>> with a 125 ohm non-inductive resistor and the unbalanced RF input is in >>>> series with a 50 pF capacitor. Both interfaces do not include the >>>> generator's output impedance. >>>> >>>> As for the sensitivity not being what the R-390/URR or the R-390A/URR is >>>> capable of, well there are perhaps 100's of tests that the receiver must >>>> successfully pass before it is accepted. Tightening any of the specs to >>>> exactly what the receiver may be capable of passing will guarantee that no >>>> one receiver will ever pass all of the acceptance tests. Then there is >>>> the added problem of your test equipment's error tolerance and being >>>> traceable back to the NIST standards. Is your 10 microvolts from the >>>> signal generator really 10 microvolts? >>>> >>>> Unless otherwise stated, the specification calls out a value that the >>>> receiver must do better than. A sensitivity of just under 6.5 microvolts >>>> for a 10 dB S+N/N with an audio power output of 10 milliwatts seems >>>> reasonable over the range of 2 to 32 MHz for either balanced or unbalanced >>>> RF inputs. This is perhaps typical for just about all HF receivers built >>>> for the military, at least for what I am aware of, but I am sure that >>>> there will be the rare exception. >>>> >>>> Regards, >>>> Jim >>>> Logic: Method used to arrive at the wrong conclusion, with confidence. >>>> Murphy >>>> >>>> On Friday, October 4, 2024 at 09:39:26 AM CDT, Bob Camp <kb...@n1k.org> >>>> wrote: >>>> >>>> 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 >>>> ______________________________________________________________ >>>> 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 > > ______________________________________________________________ > 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
