[R-390] R390a and SDR

Tue Apr 23 02:49:52 EDT 2019

Jay's document is an excellent read. Thanks for sharing.

Alan

On Mon, Apr 22, 2019 at 9:46 PM Larry H <larry41gm at gmail.com> wrote:

> Since you might be using Bandwidth in a formula, keep in mind that the
> R-390A bandwidths are not necessarily dead on.  The specs for 4 kc and
> below are usually pretty good, but 8 kc is 7.5 kh and higher, and 16 kc is
> 12 kh and higher (measured at the 50 % signal output level).  The last ones
> I measured were pretty good, but the 16 kc bandwidth can be affected by the
> stagger tuning of the IFs.  It could be wider or narrower.  So, if your
> calculation is important, you may want to measure it (see chapter 4 of the
> Y2K tech ref).
>
> Regards, Larry
>
> On Mon, Apr 22, 2019 at 8:11 PM <wb5uom at hughes.net> wrote:
>
> > Alan,
> >
> > Never have played with 16Khz Bw
> >
> > If I can remember this weekend, I may bring the equipment home and do
> some
> > playing and see.
> >
> >
> >
> > Also, here is an interesting article that you might  take a look at:
> >
> >
> >
> > http://w1vd.com/R-390ASoftRockdetails.html
> >
> >
> >
> >
> >
> > David
> >
> > WB5UOM
> >
> > Texas USA
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > From: Alan Victor <amvictor at ncsu.edu>
> > Sent: Monday, April 22, 2019 10:05 PM
> > To: wb5uom at hughes.net
> > Cc: jm <josemic at gmail.com>; 390 list <R-390 at mailman.qth.net>
> > Subject: Re: [R-390] R390a and SDR
> >
> >
> >
> > Hi David, thanks for the input.
> >
> > But I really do not see how you can use the SDR to state the sensitivity
> of
> > the 390, UNLESS  you
> > Have calibrated it (the SDR) with a accurate signal generator.
> >
> > I agree and certainly did not make that inference, I hope. I believe all
> > of this discussion is based on bench measurements from nice sources and
> NO
> > ANTENNA. Just box to box calculations. An R390A to a pan adapter and what
> > is possible was my understanding. It would be useful to look at some
> bench
> > measurements and then correlate those numbers to the performance of the
> pan
> > adapter. In the end, without modification of the 390A at 16 kHz BW what
> is
> > the minimum BENCH discernible signal level?  Alan
> >
> >
> >
> > On Mon, Apr 22, 2019 at 6:07 PM <wb5uom at hughes.net <mailto:
> > wb5uom at hughes.net> > wrote:
> >
> > Well, I decided to chime in here, hopefully I will not offend anyone.
> >
> > I have 3 R-390A's as well as a gathering of other "classic" Hf receivers,
> > and I have several SDR's as well.
> >
> > I have played with the R-390 as the 'front end' to the SDR and it is fun
> to
> > play with.
> >
> > But I really do not see how you can use the SDR to state the sensitivity
> of
> > the 390, UNLESS  you
> > Have calibrated it (the SDR) with a accurate signal generator.
> >
> > I am lucky enough (on some days) to work in the commercial communications
> > field, and happen to own a
> > AEROFLEX 3920 service monitor that does SSB (and AM too).
> >
> > Now I have gotten frowns from others on various lists, but the 3920's
> > generate function is calibrated down to -138Dbm.
> > IF  I say IF I use the MDS method (minimum discernable signal) on SSB -
> > using a 1000khz test tone, I can hear that test tone
> > All the way to the bottom on the 390's and the Winradio 313i
> > Does that mean I could copy a SSB station that weak, nope, because the
> tone
> > is a steady signal and a voice ssb as we know is not.
> > (And I am part deaf after all these years of listening to a 1khx test
> tone,
> > so I have to wear headphones when I do this)
> >
> > I have never been a fan of the 12db sinad test, since in the 2way
> > communications business we use the 20db sinad.
> >
> > At 20db sinad, my 390's will do around -109Dbm as will my Winradio 313i
> on
> > SSB
> >
> > Now that you all have my mind going on this, I guess I need to bring the
> > 3920 home and see what the SDRplay RSPduo will really do.
> >
> > Just my 2 cents worth.
> >
> > David
> >
> > WB5UOM
> > Texas USA
> >
> >
> >
> > -----Original Message-----
> > From: r-390-bounces at mailman.qth.net <mailto:
> r-390-bounces at mailman.qth.net>
> > <r-390-bounces at mailman.qth.net <mailto:r-390-bounces at mailman.qth.net> >
> On
> > Behalf Of Alan Victor
> > Sent: Monday, April 22, 2019 6:54 PM
> > To: jm <josemic at gmail.com <mailto:josemic at gmail.com> >
> > Cc: 390 list <R-390 at mailman.qth.net <mailto:R-390 at mailman.qth.net> >
> > Subject: Re: [R-390] R390a and SDR
> >
> > Hello again.
> >
> > I did not imply that the R390A was limited to -100 dbm at its INPUT. I
> > indicated that its noise power at its output might be as high as -100
> dBm.
> > Most likely higher, Lets consider the sensitivity equation. Its pretty
> > straight forward.
> >
> > Sens (dBm) = -174 + 10 log (BW) + NF (dB) + S+N/N ratio in dB for desired
> > intelligibility.
> >
> > Lets plug in some typical numbers. BW: 3 kHz, NF: 10 dB, S+N/N: 10 dB
> >
> > Then SENS is -174+30+10+10 = -124 dBm. Obviously if we reduce the BW by
> > another order of magnitude then we could achieve -134 dBm and so on. The
> > noise power OUT would be dictated by the input sensitivity or the NF
> > multiplied by the total forward gain of the receiver. Additional gain
> could
> > be added as required as long as we don't compromise distortion, IMD,
> etc...
> > Alan
> >
> > On Mon, Apr 22, 2019 at 3:45 PM jm <josemic at gmail.com <mailto:
> > josemic at gmail.com> > wrote:
> >
> > > John
> > >
> > > Very clear and educational.
> > >
> > > Many thanks
> > >
> > > Jose
> > > ______________________________________________________________
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