[R-390] Official specs

Fri Oct 4 13:00:47 EDT 2024

@Bob - I fully agree. They had to guarantee the full coverage 0.5-32 MHz on 100% of production, while I do the test in few points… too easy for me! 😀

> Il giorno 4 ott 2024, alle ore 18:53, Jim Whartenby via R-390 <r-390 at mailman.qth.net> ha scritto:
> 
> 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 <kb8tq at 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 at 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 <n4buq at 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 at 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 <larry41gm2 at 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 at mailman.qth.net <mailto:r-390 at 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
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