[R-390] r390a and SDR

[Alan Victor]

Hi Martin and others,

I was trying to clarify the original query posted by Jose. In any case, I
suspect that the SDR could be treated no different than a spectrum analyzer
or a swept receiver with a noise floor. The question is, does the R390A
have a selected bandwidth (BW) which could provide sufficient noise power
output to display on the SDR? If not, either the SDR noise floor must be
lowered, add a low noise preamplifier, or the bandwidth of the R390A must
be increased. I took the example of its widest bandwidth, 16 kHz, that is
10 log BW or 40 dB above kTB; -174 dBm. Hence, the 390A at zero dB noise
figure would generate a -100 dBm noise power floor. Well, the NF is not
zero in the 390A, so that would further raise the floor. Furthermore, 16
kHz BW may not be wide enough to be of much value for a SDR display. So it
seems like addressing the construction of an outboard IF strip taken
directly from the 390A and bypassing its internal module may make sense. I
believe that was Larry's point.

In any case doing both, decreasing the SDR noise floor, and adding a  high
IP3 low noise preamp to the SDR and an independent wide band IF to the 390A
would make a nice listening post. My 2 cents. Alan

On Mon, Apr 22, 2019 at 4:17 AM Martin Sole <hs0zed at gmail.com> wrote:

> It belongs to the sdr most likely, and can be made to show whatever you
> like by adjustment of some sdr controls, depending on the software and
> driver. Quite often you can adjust the gain of the sdr device which
> essentially moves the "grass" that which shows as random noise in the
> spectrum display. This is purely a relative figure, unless calibrated,
> and most likely bears no relationship to the performance of the receiver
> to which it is attached as a detector at the receivers IF. Much will
> also depend on the gain in the receiver between the antenna port and the
> IF output.
>
> I don't know the R390 that well but I doubt the noise level present at
> the IF output is much lower than -100dBm possibly it is even higher than
> that. I expect there is significant amplification between the antenna
> connector and the IF output.
>
> Martin, HS0ZED
>
>
> On 22/04/2019 18:08, jm wrote:
> > Hi Alan,
> >
> > The noise floor that I can see in the sdr software (-100 dbm) belongs to
> > the sdr device or to the r390a receiver?
> >
> > Your explanation is about a noise floor of -100 dbm. This level  could be
> > considered as low if  the comments of Chuck Rippel are taken into account
> > (up to -143 db in exceptional cases).
> >
> > Is my receiver performance below its possibilities?
> >
> > Thanks
> >
> > <
> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
> >
> > Libre
> > de virus. www.avast.com
> > <
> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
> >
> > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at 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 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>