[R-390] r390a and SDR

[Alan Victor]

Hi Larry, Jose.

If the R390A is set to 16 kHz BW that is a noise power 40 dB above kTB or
-100 dBm.
If the NF of the 390A is say 10 dB that would at least place the noise
floor at -90 dBm. Perhaps additional
gain would be required to improve the S/N ratio at the display.

What am I missing? Is the noise floor of the pan adapter much higher? Hence
we require a wider BW
prior to applying signal to the adapter.

Thanks, Alan



On Fri, Apr 19, 2019 at 1:02 AM jm <josemic at gmail.com> wrote:

> Thanks Larry. 50-60 khz would be a good improvement.
>
> Regards, Jose
>
> El vie., 19 abr. 2019 a las 9:00, jm (<josemic at gmail.com>) escribió:
>
> > Hi Larry
> >
> > Many thanks for your answer. Sorry that I'm not very familiar with the
> > terms. I think thas it's called the noise floor. In my layman words the
> > place where the signal begins. I have checked different sdr receivers and
> > the point (I suppose the noise floor?) where the signal appears is
> > different. For example in the sdrplay the figure is -90 db. In the case
> of
> > the combination Funcube/r390 is -100db. My doubt is whether that figure
> of
> > -100db corresponds to the sdr receiver of to the 390.  I am not sure if
> my
> > explanation now is clear enough.
> >
> > Thanks
> >
> > El vie., 19 abr. 2019 a las 5:53, Larry H (<larry41gm at gmail.com>)
> > escribió:
> >
> >> Hi Jose,  In reference to increasing the bandwidth, it might be possible
> >> to increase it to 50 or 60 kh, but I doubt any more than that.  In
> order to
> >> do that, you would need to bypass the 16 kh filter in the IF deck.  You
> >> would also need to put a custom filter in it's place to increase the
> gain
> >> of the skirts, so the result would be some what flat.  The R390s were
> >> designed to not have a panoramic bandwidth.
> >>
> >> Regards, Larry
> >>
> >> On Thu, Apr 18, 2019 at 3:56 PM jm <josemic at gmail.com> wrote:
> >>
> >>> Hi fellows!
> >>>
> >>> Taking advantage of the IF external connection of the receiver, I have
> >>> been
> >>> using it with my SDR dongle. It is a Funcube pro+ and the  sdr software
> >>> is
> >>> Gqrx running under linux. I have to thank my son the program settings
> and
> >>> his willingness to help me with the obscure world of linux.   The
> >>> combination of both new and old technology runs smoothly.
> >>>
> >>> Obviously, the program is tuned to 455 kcs and the bandwith used in the
> >>> 390
> >>> is its maximum capability,  16 kcs.
> >>>
> >>> I am impressed by the technical level of the people in the list and
> hope
> >>> not to be an annoying beginner that makes silly questions.
> >>>
> >>> In spite of the above, here are my questions:
> >>>
> >>> 1. I was surprised about the floor level in the sdr sofware. The floor
> is
> >>> -100 db which is very low, in my opinion, according to what I have read
> >>> about the 390. I don't aspire to have a receiver whith a 'galactic
> level'
> >>> as Mr. Rippel says, but this is far from expected. Does that level
> >>> correspond to the r390 or is it the sdr receiver level (funcube)?
> >>>
> >>> 2. I read somewhere that it is possible to feed the sdr receiver
> through
> >>> some point of the 390 with the result of obtaining a much widest
> >>> bandwidht.
> >>> I remember that could be extended to 1 mhz. The current 16khz is
> >>> appropriate for amateurs chunks of bands but in broadcasting the
> >>> reception
> >>> is limited to only one station.
> >>>
> >>> Many thanks as always and happy Easter!
> >>>
> >>> Jose
> >>> EA8DCP
> >>> ______________________________________________________________
> >>> 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