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
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