Yes I see the problem regarding the two inputs, so I
went back and re-familiarized myself a bit with
Spectrogram since its been awhile since I've used it.
After experimenting with V6.x briefly this afternoon I
see that it can give you some sense of a filters
passband shape but would be a bit more work to
interpret since it doesn't easily provide a nice
amplitude (X) vs. frequency display (Y) presentation.
Its amplitude is always presented in the Z-axis (by
color shade and/or brightness) from what I can tell.
I guess the way that I would proceed then is to feed
each radio the same strength signal (exact level not
critical) from a signal generator. Then sweep it
across the filters pass bandwidth quickly. Be sure to
span the filter's full bandpass (plus some) bandwidth
before it scrolls off of the screen and then hit
Spectrogram's STOP. Won't be easy but should be
doable. Then note the color/brightness contour of that
sweep. I also see that Spectrogram has a tool to
provide relative signal strength using a cross-hair
pointer, just trace the sweep with that pointer, from
that you can directly read signal strength vs.
frequency. Definitely not a quick visual way to see
filter passband shape but it should work. I also see
that V6 of Spectrogram provides sampling rates to
48kHz so it should work good to see any nasties or
other garbage out to ~20kHz.
Also to address Barry N1EU's question about relative
signal strength settings between the two radios I
would use a similar methodology. First set up the
signal generator at some modest level, again the
actual level is somewhat arbitrary for this test as
well. Then adjust the controls of both radios to
provide the EXACT same relative strength for the
recovered audio for that signal generator tone for
both sides of the Spectrogram. That way the recovered
signal becomes the baseline and then the relative
quietness or noisiness of the two radios can be
directly compared. Perhaps not totally scientific but
should be reasonably realistic. It may be worth doing
this test with several different signal generator
levels to provide additional data about AGC behavior
between the two radios. Can also be used to provide
more information about DSP NR performance etc.
Duane
N9DG
--- Steve N4LQ <n4lq@iglou.com> wrote:
> I'm trying Spectran but don't see that it can show 2
> inputs at once.
> Spectrogram is too expensive but at least you can
> display 2 radios. Do you
> know of any others that can do that?
> Steve N4LQ
> ----- Original Message -----
> From: "Duane - N9DG" <n9dg@yahoo.com>
> To: <tentec@contesting.com>
> Sent: Sunday, December 26, 2004 9:49 AM
> Subject: Re: [TenTec] Re: More PRO III/Omni VI pix
>
>
> > I'd be curious what the audio spectrums look like
> for these two radios in the frequency domain vs. the
> time domain that these JPEG's are done in?
> >
> > It is always interesting to see what audio
> artifacts a
> > radio puts out clear out to 20 kHz or so. I've
> come to
> > believe that these artifacts above 3Khz or so are
> >a factor in whether a radio is fatiguing to listen
> to or not.
> >
> > I use Spectran and SR5 for looking at these
> traits;
> > they can be found at:
> >
> > http://www.weaksignals.com/
> >
> > http://www.ar5.ndo.co.uk/
> >
> > And there are a number of other programs out there
> as well and most are freeware.
> >
> > It is easy to get a good sense of IF filter
> passband flatness with these programs as well
> (assuming that
> > the sound card you are using has flat response).
> >
> > Duane
> > N9DG
> >
> >
> > --- Steve N4LQ <n4lq@iglou.com> wrote:
> >
> >> To answer the SSB question. Here is a picture of
> >> both rigs listening to band
> >> noise on 80 meters without the NR turned on and
> with
> >> the bandwidth at 1.8
> >> khz.
> >> Notice how the Omni VI's pattern is elevated off
> the
> >> bottom of the chart.
> >> This demonstrates the lack of low frequency
> response
> >> of the TenTec filters.
> >> Note the noise spikes kick up to about 3.5 khz on
> >> the Omni but nearly 4.5
> >> khz on the PRO.
> >> The main thing to note here is the density of the
> >> noise. The PRO's pattern
> >> is almost solid blue while the Omni's is much
> less
> >> intense. Also look at the
> >> top pattern. The PRO III's signal is
> significantly
> >> more intense.
> >> Obviously, the Omni VI is going to be much easier
> on
> >> the ears under these
> >> conditions. Those big noise spikes come out
> sounding
> >> like clicks on the PRO
> >> but are hardly noticeable on the Omni.
> >> Keep in mind....My PRO III is being checked out.
> It
> >> could be defective. The
> >> jury is still out on this one.
> >> http://www.webham.com/ssb.jpg
> >>
> >>
> >> Steve N4LQ
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