--- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:

>  - This signal is called "MDS" even though it is quite high, 10 - 100 times
the average voltage of the noise itself and easily audible on the receiver.

I don't understand this statement.

Although the MDS and noise are spectrally quite different, if the MDS power and
the noise power in the resolution bandwidth are the same e.g. -150dBm, then the
RMS value of the MDS and the noise in that bandwidth are also the same.

>  - One objective definition of dynamic range would be the difference between
the noise floor or MDS and the highest level that causes objective indication of
overload.
>

Yes.  But you need to define "MDS" and "objective indication of overload" in
order to measure it.

> So, in order to compare dynamic range one would need to specify the resolution
bandwidth, the noise measurement methodology, and the overload detection
methodology.
>

Exactly.

> I guess my only problem with this is it seems to be a meaningless spec except
for comparison. It does not tell me the weakest signal my receiver can hear and
the only way I would know that is by experience after knowing the spec for a
particular receiver.

'Twas ever thus.  To be pedantic it does not tell you the weakest signal _you_
can hear on your receiver.

Reminds me of the THD specs for hi-fi amplifiers.  I've heard amplifiers with
low THD that sound foul when playing real music.

The world is full of meaningless specs.

But you need an objective measure so that you can compare Receiver A with
Receiver B.  The best you can do is choose a measure that has as much meaning in
the real world as possible, and hope others agree.

Personally I like Two Tone Dynamic Range as specified in the ARRL Handbook.

73

Nick G3VNC

Completely agree.... the RMS value as measured on a voltmeter at the speaker
terminals is the same. However, if you look at the two signals superimposed on a
spectrum display, the noise power is dispersed across the bandwidth of the
filter. The signal power is concentrated in a single "spike" and, therefore,
measures about 20 dB higher at it's peak.

The total power of the noise and the signal are the same. The power of the
signal generator is focused on a very narrow bandwidth and, therefore, appears
to be much greater on a spectrum display.

Warren Allgyer - W8TOD

--- In softrock40@yahoogroups.com, "g3vnc" <g3vnc@...> wrote:
>
> --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@> wrote:
>
> >  - This signal is called "MDS" even though it is quite high, 10 - 100 times
the average voltage of the noise itself and easily audible on the receiver.
>
> I don't understand this statement.
>
> Although the MDS and noise are spectrally quite different, if the MDS power
and the noise power in the resolution bandwidth are the same e.g. -150dBm, then
the RMS value of the MDS and the noise in that bandwidth are also the same.
>

Spaced at exactly 1kHz. Definitely local, maybe even generated inside the
soundcard. Does it disappear when the antenna is disconnected? Or when the
Softrock is disconnected?
One observation is that the noise floor from the Softrock is very low. If you
add some recording gain in the Windows sound mixer and raise the floor to
-105..-100dB, these lines may disappear.

73, Mike

--- In softrock40@yahoogroups.com, Chris Wilson <chris@...> wrote:
>
>
>
>   17/02/2013 15:53
>
> Sometimes on 15 meters my bandscope shows the vertical lines in the
> link to the screenshot of HDSDR The white outline shows the display
> when I change to 12 and 17 meters. It sometimes suddenly appears, for
> several hours. Closing and re opening the app, or CFGSR makes no
> difference. It's displaying from my Softrock Ensemble II receiver. Thanks.
>
> http://www.chriswilson.tv/hdsdr.jpg
>
> --
>        Best Regards,
>                    Chris Wilson.   2E0ILY
> mailto: chris@...
>

>
> Spaced at exactly 1kHz. Definitely local, maybe even generated
> inside the soundcard. Does it disappear when the antenna is
> disconnected? Or when the Softrock is disconnected?
> One observation is that the noise floor from the Softrock is very
> low. If you add some recording gain in the Windows sound mixer and
> raise the floor to -105..-100dB, these lines may disappear.

> 73, Mike



18/02/2013 17:35

Yes, it must be local, but what gives exact 1 kHz signals? I have done
nothing at all, the Softrock's been powered up all the time since that
screen shot, here's a current one, same band, all looks fine...

http://www.chriswilson.tv/hdsdr2.jpg

Next time it does it I'll disconnect, then ground the antenna socket.
Just disconnecting it from my 590, and connecting straight to the
antenna doesn't change things. I thought it might be something
generated inside the TS-590 where it acts as a second receiver cum
panadaptor. Will try what you suggest next time, but suspect it's
actually pulling this from the air waves round here.

Thanks Mike!

--
        Best Regards,
                    Chris Wilson.   2E0ILY

I still suggest you increase the gain of your soundcard. Even your "clean"
spectrum would be much nicer. It looks like you are using "Line In" instead of
the microphone input, or like you have the recording level turned way down in
the Windows sound mixer.
I have seen all kinds of spurs when the gain is this low.
Read the currently ongoing discussion about the dynamic range of the Softrock.
In your case you are not using the whole available range and your sensitivity is
not optimal.

73, Mike

--- In softrock40@yahoogroups.com, Chris Wilson <chris@...> wrote:
>
>
>
> >
> > Spaced at exactly 1kHz. Definitely local, maybe even generated
> > inside the soundcard. Does it disappear when the antenna is
> > disconnected? Or when the Softrock is disconnected?
> > One observation is that the noise floor from the Softrock is very
> > low. If you add some recording gain in the Windows sound mixer and
> > raise the floor to -105..-100dB, these lines may disappear.
>
> > 73, Mike
>
>
>
> 18/02/2013 17:35
>
> Yes, it must be local, but what gives exact 1 kHz signals? I have done
> nothing at all, the Softrock's been powered up all the time since that
> screen shot, here's a current one, same band, all looks fine...
>
> http://www.chriswilson.tv/hdsdr2.jpg
>
> Next time it does it I'll disconnect, then ground the antenna socket.
> Just disconnecting it from my 590, and connecting straight to the
> antenna doesn't change things. I thought it might be something
> generated inside the TS-590 where it acts as a second receiver cum
> panadaptor. Will try what you suggest next time, but suspect it's
> actually pulling this from the air waves round here.
>
> Thanks Mike!
>
> --
>        Best Regards,
>                    Chris Wilson.   2E0ILY
>

----- Original Message -----
Subject: Re: [softrock40] Re: What might be the cause of this HDSDR display
please?


>
> Yes, it must be local, but what gives exact 1 kHz signals? I have done
> nothing at all, the Softrock's been powered up all the time since that
> screen shot, here's a current one, same band, all looks fine...
>

Chris,

I think I've seen people say that the USB can cause this. Maybe an intermittent?
But, yes, find out where it is coming in, check local equipment.

I'm not sure about Mike's advice to increase gain. I have good results with that
sort of noise floor, maybe you have calibrated
HDSDR? If so then leave it. Yes, it is possible to cover up signals not coming
in through the antenna but I'd say get rid of them if
you can.

73 Alan G4ZFQ

> http://www.chriswilson.tv/hdsdr2.jpg
>
> Next time it does it I'll disconnect, then ground the antenna socket.
> Just disconnecting it from my 590, and connecting straight to the
> antenna doesn't change things. I thought it might be something
> generated inside the TS-590 where it acts as a second receiver cum
> panadaptor. Will try what you suggest next time, but suspect it's
> actually pulling this from the air waves round here.
>

I was intrigued by this:
https://en.wikipedia.org/wiki/Long_delayed_echo
I have heard the long path echoes and around-the-world signals from nearby
stations before, but nothing out of the ordinary. Yet it looks like there are
some very interesting phenomena to study, and we now have affordable tools to do
this.

Because the round-the-world signals are naturally focused at the point of
origin, I would expect them to be easily detectable with low power using SDR and
DSP algorithms. All I need is software that transmits a signal, quickly switches
to RX and listens to the echo. Because the signal is known and coherent,
correlation method should be very sensitive. Maybe it is even possible to detect
the Moon bounce?

The question about the Softrock RXTX hardware is how quickly it can switch from
TX to fully sensitive RX?

73, Mike VE3YXA

Warren

I just measured the 2 Tone Dynamic Range of my Softrock Ensemble Rx and Delta 44
sound card.

TEST SETUP

TenTec Delta 580 VFO set to 5057kHz.  Power output +4dBm.

Homebrew VFO set to 5052kHz.  Power output +4dBm.

Two 20dB attenuators at each VFO output.

Homebrew 6dB hybrid combiner.  Power output -22dBm per tone.

Softrock Ensemble Rx.  Delta 44 sound card.  Linrad set with resolution
bandwidth 1kHz.

RESULTS

MDS = -116dBm in 1kHz

Input Intercept = +20dBm

Two Tone Dynamic Range = 2*(20+116)/3 = 91dB in 1kHz

Nick

I hope that this is not redundant since I have not read all of the posts in this thread. The conventions that have evolved for defining SNR, MDS etc have all come from a history where the ultimate receiver of the signal is someone's ear. In that context, the noise and it's relationship to the bandwidth make sense because the ear doesn't have the ability to ignore noise at one frequency while paying attention to noise at another frequency. The ear hears all of the noise in the passband of the filter and it obscures the intended signal even if it is not at the same frequency as the intended signal. When you switch to a world of FFTs and "visual reception", the story changes. When the eye is the receiver, the presentation of the signal and noise allow for the possibility of ignoring noise that is in the filter bandwidth but not at the same frequency as the signal. The effect of ignoring the noise off to the sides is to narrow the filter bandwidth to the width of the signal. In an FFT display, this is the FFT "equivalent noise bandwidth". In an NDB receiver project that I have been working on that used SpectrumLab, I defined two SNR's. One I called the Visual SNR and the other the Aural SNR. Aural SNR is the traditional SNR where the signal is ratioed with the noise in the specified filter bandwidth. It improves as the filter narrows and is unaffected by the FFT bin width. Visual SNR is the ratio of the signal to the noise with a bandwidth equal to the FFT bin equavelent bandwidth. This is what the eye sees on an FFT display.
 
Tony

 

---

To: softrock40@yahoogroups.com
From: allgyer@...
Date: Mon, 18 Feb 2013 16:01:51 +0000
Subject: [softrock40] Re: Softrock Dynamic Range and MDS Redux

 

Completely agree.... the RMS value as measured on a voltmeter at the speaker terminals is the same. However, if you look at the two signals superimposed on a spectrum display, the noise power is dispersed across the bandwidth of the filter. The signal power is concentrated in a single "spike" and, therefore, measures about 20 dB higher at it's peak.

The total power of the noise and the signal are the same. The power of the signal generator is focused on a very narrow bandwidth and, therefore, appears to be much greater on a spectrum display.

Warren Allgyer - W8TOD

--- In softrock40@yahoogroups.com, "g3vnc" wrote:
>
> --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
>
> > - This signal is called "MDS" even though it is quite high, 10 - 100 times the average voltage of the noise itself and easily audible on the receiver.
>
> I don't understand this statement.
>
> Although the MDS and noise are spectrally quite different, if the MDS power and the noise power in the resolution bandwidth are the same e.g. -150dBm, then the RMS value of the MDS and the noise in that bandwidth are also the same.
>

Thank you Milt and Tony! A wonderful explanation of the phenomenon I have been
observing.

My follow-on question would be: Could we incorporate the spectral noise level on
the FFT display into the calculations of MDS and dynamic range and, if so, how?

Warren Allgyer - W8TOD

--- In softrock40@yahoogroups.com, Milt Cram <w8nue@...> wrote:
>
> On 2/18/2013 2:55 PM, Anthony Casorso wrote:
> >
> >
> > I hope that this is not redundant since I have not read all of the
> > posts in this thread. The conventions that have evolved for defining
> > SNR, MDS etc have all come from a history where the ultimate receiver
> > of the signal is someone's ear. In that context, the noise and it's
> > relationship to the bandwidth make sense because the ear doesn't have
> > the ability to ignore noise at one frequency while paying attention to
> > noise at another frequency. The ear hears all of the noise in the
> > passband of the filter and it obscures the intended signal even if it
> > is not at the same frequency as the intended signal. When you switch
> > to a world of FFTs and "visual reception", the story changes. When
> > the eye is the receiver, the presentation of the signal and noise
> > allow for the possibility of ignoring noise that is in the filter
> > bandwidth but not at the same frequency as the signal. The effect of
> > ignoring the noise off to the sides is to narrow the filter bandwidth
> > to the width of the signal. In an FFT display, this is the FFT
> > "equivalent noise bandwidth". In an NDB receiver project that I have
> > been working on that used SpectrumLab, I defined two SNR's. One I
> > called the Visual SNR and the other the Aural SNR. Aural SNR is the
> > traditional SNR where the signal is ratioed with the noise in the
> > specified filter bandwidth. It improves as the filter narrows and is
> > unaffected by the FFT bin width. Visual SNR is the ratio of the signal
> > to the noise with a bandwidth equal to the FFT bin equavelent
> > bandwidth. This is what the eye sees on an FFT display.
> >
> > Tony
> >
> >
> > ------------------------------------------------------------------------
> > To: softrock40@yahoogroups.com
> > From: allgyer@...
> > Date: Mon, 18 Feb 2013 16:01:51 +0000
> > Subject: [softrock40] Re: Softrock Dynamic Range and MDS Redux
> >
> > Completely agree.... the RMS value as measured on a voltmeter at the
> > speaker terminals is the same. However, if you look at the two signals
> > superimposed on a spectrum display, the noise power is dispersed
> > across the bandwidth of the filter. The signal power is concentrated
> > in a single "spike" and, therefore, measures about 20 dB higher at
> > it's peak.
> >
> > The total power of the noise and the signal are the same. The power of
> > the signal generator is focused on a very narrow bandwidth and,
> > therefore, appears to be much greater on a spectrum display.
> >
> > Warren Allgyer - W8TOD
> >
> > --- In softrock40@yahoogroups.com
> > <mailto:softrock40%40yahoogroups.com>, "g3vnc" wrote:
> > >
> > > --- In softrock40@yahoogroups.com
> > <mailto:softrock40%40yahoogroups.com>, "warrenallgyer" wrote:
> > >
> > > > - This signal is called "MDS" even though it is quite high, 10 -
> > 100 times the average voltage of the noise itself and easily audible
> > on the receiver.
> > >
> > > I don't understand this statement.
> > >
> > > Although the MDS and noise are spectrally quite different, if the
> > MDS power and the noise power in the resolution bandwidth are the same
> > e.g. -150dBm, then the RMS value of the MDS and the noise in that
> > bandwidth are also the same.
> > >
> >
> >
> >
> Hi all,
>
> In all of the discussion thus far, I have heard no mention of "power
> spectral density".  In SDR applications, where an FFT is usually used to
> produce a spectral display, we see such a power spectral density.  That
> is, the display indicates the power versus frequency.  When using the
> FFT, the minimum frequency resolution is the "bin width".  If the scale
> of the spectral display is calibrated in watts, then each bin represents
> a certain number of watts divided by the bin width in Hz.  If one then
> introduces the bandwidth of the particular operating mode,  the total
> noise power is the integral (sum) of the power spectral density over the
> bandwidth--e.g. the observed power in an FFT bin times the number of
> bins within the bandwidth.  For CW, where the signal may be contained
> within a single bin, and noise is distributed over many bins, equal
> noise and signal power means that the noise level on the spectral
> display could appear to be much less than the signal.  However, if one
> was operating FM, with the signal smeared over the entire operating
> bandwidth, the signal would be difficult to separate from the
> noise--even with the same SNR as in the case of CW.  PSK 31 is another
> example of where the signal energy(power) may be concentrated in one or
> two bins of the FFT spectral display.
>
> If the length of the FFT is long, the bin width can be quite small--i.e.
> a few Hz.  If the length of the FFT is short, the bin width may be
> measured in kHz.
>
> In addition, it should now be clearly evident why one is able to "copy"
> a CW signal using a narrow band filter, when it may be difficult, or
> impossible, when using a wide bandwidth filter.  If the filter bandwidth
> nears the bin width, the SNR will be significantly improved.
>
> In summary--don't be confused by the spectral display when considering
> SNR, MDS, and dynamic range.
>
> My 2 cents--
> Milt
> W8NUE
>

windows does not recognize anything in the X86 directory as being a driver

-- John Williams
KE5SSH - ham since 2007
WQKA523 - GMRS for family use on the farm

Chris

I am guessing you are suffering overload from a very strong local signal that is
in the filter bandpass of the receiver. I see a very similar display on 40
meters when the local shortwave broadcaster comes on the air on 7280 KHz and I
can measure his signal on my antenna at -10 dBm. That equates to 60+ dB over S9.

I have to disagree strongly with the advice that you increase your sound card
gain. If this is indeed overload then you will make the problem worse by
increasing the gain. I recommend running the sound card with minimum gain in
order to minimize exactly this problem.

Warren Allgyer - W8TOD

--- In softrock40@yahoogroups.com, Chris Wilson <chris@...> wrote:
>
>
>
>   17/02/2013 15:53
>
> Sometimes on 15 meters my bandscope shows the vertical lines in the
> link to the screenshot of HDSDR The white outline shows the display
> when I change to 12 and 17 meters. It sometimes suddenly appears, for
> several hours. Closing and re opening the app, or CFGSR makes no
> difference. It's displaying from my Softrock Ensemble II receiver. Thanks.
>
> http://www.chriswilson.tv/hdsdr.jpg
>
> --
>        Best Regards,
>                    Chris Wilson.   2E0ILY
> mailto: chris@...
>

Chris

One additional thought that came shortly after hitting "SEND"....

If it is overload, and if you have a scope, you can probe the crossover jumpers
on the IQ audio output. If the receiver is overloading you will see peak to peak
audio signals in the range of 4-5 V P-P. These signals can be well outside the
displayed frequencies on HDSDR. You can also flip up and down the band, 100 KHz
at a time, to find the offender. I would look +- at least 5 MHz. I am betting
you will find something hitting the peg on your S meter in that range.

Warren Allgyer - W8TOD
--- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:
>
> Chris
>
> I am guessing you are suffering overload from a very strong local signal that
is in the filter bandpass of the receiver. I see a very similar display on 40
meters when the local shortwave broadcaster comes on the air on 7280 KHz and I
can measure his signal on my antenna at -10 dBm. That equates to 60+ dB over S9.
>
> I have to disagree strongly with the advice that you increase your sound card
gain. If this is indeed overload then you will make the problem worse by
increasing the gain. I recommend running the sound card with minimum gain in
order to minimize exactly this problem.
>
> Warren Allgyer - W8TOD
>
> --- In softrock40@yahoogroups.com, Chris Wilson <chris@> wrote:
> >
> >
> >
> >   17/02/2013 15:53
> >
> > Sometimes on 15 meters my bandscope shows the vertical lines in the
> > link to the screenshot of HDSDR The white outline shows the display
> > when I change to 12 and 17 meters. It sometimes suddenly appears, for
> > several hours. Closing and re opening the app, or CFGSR makes no
> > difference. It's displaying from my Softrock Ensemble II receiver. Thanks.
> >
> > http://www.chriswilson.tv/hdsdr.jpg
> >
> > --
> >        Best Regards,
> >                    Chris Wilson.   2E0ILY
> > mailto: chris@
> >
>

>
> Chris

> I am guessing you are suffering overload from a very strong local
> signal that is in the filter bandpass of the receiver. I see a very
> similar display on 40 meters when the local shortwave broadcaster
> comes on the air on 7280 KHz and I can measure his signal on my
> antenna at -10 dBm. That equates to 60+ dB over S9.

> I have to disagree strongly with the advice that you increase your
> sound card gain. If this is indeed overload then you will make the
> problem worse by increasing the gain. I recommend running the sound
> card with minimum gain in order to minimize exactly this problem.

> Warren Allgyer - W8TOD


18/02/2013 22:36

I need to do some more testing. I got a similar signal on 10 meters
this afternoon. Disconnecting the antenna at the Softrock antenna
connector made no difference. Nor did grounding the centre pin of the
connector to the outer sleeve. Fiddling with the USB connectors did
make a difference. I believe it may be a further grounding issue. I
connected my TS-590 case to the case of my PC and fixed a very
annoying tocking noise that my ACLog software caused whilst polling
the 5090's frequency for automatic frequency and band logging. I
suspect a further ground loop may be occurring, something related to
the USB stuff. I will see if I can add a further ground next time I
see this. I am now pretty sure it is NOT a local signal. There are no
broadcast TX's for many many miles. Thanks Warren, Alan and Mike.

--
        Best Regards,
                    Chris Wilson.   2E0ILY

On 2/18/2013 3:43 PM, warrenallgyer wrote:
> Thank you Milt and Tony! A wonderful explanation of the phenomenon I have been
observing.
>
> My follow-on question would be: Could we incorporate the spectral noise level
on the FFT display into the calculations of MDS and dynamic range and, if so,
how?
>
> Warren Allgyer - W8TOD
>
>
Hi Guys,

Re: Minimum Detectable Signal and Minimum Discernable Signal
If you haven't already read this--take a look.

http://www.ittc.ku.edu/~jstiles/622/handouts/Minimum%20Detectable%20Signal.pdf

Milt
W8NUE

Hello Gentlemen

I have a question if someone could help me in this topic

Well, I have my desktop radio FT-1000D as well as Softrock I use,

and I would like at the same time have the opportunity to listen to the same
antenna

on one and the other radio (FT-1000 and Softrock) and when I want to
transmit

to the FT-1000D is want him to Softrock was automatically disconnect and
shorted to ground

if anyone has a proven systems and could help me?

Thanks

73 , Jakub SQ8J

When operating at Full Speed, USB sends a Start Of Frame each millisecond. With
light buss traffic (and poor USB shielding) this might be visible. Try a new USB
cable.

73, Ed WX4S (who is reading USB Complete in his spare moments)

--- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
>
>
> ----- Original Message -----
> Subject: Re: [softrock40] Re: What might be the cause of this HDSDR display
please?
>
>
> >
> > Yes, it must be local, but what gives exact 1 kHz signals? I have done
> > nothing at all, the Softrock's been powered up all the time since that
> > screen shot, here's a current one, same band, all looks fine...
> >
>
> Chris,
>
> I think I've seen people say that the USB can cause this. Maybe an
intermittent?
> But, yes, find out where it is coming in, check local equipment.
>
> I'm not sure about Mike's advice to increase gain. I have good results with
that sort of noise floor, maybe you have calibrated
> HDSDR? If so then leave it. Yes, it is possible to cover up signals not coming
in through the antenna but I'd say get rid of them if
> you can.
>
> 73 Alan G4ZFQ
>
> > http://www.chriswilson.tv/hdsdr2.jpg
> >
> > Next time it does it I'll disconnect, then ground the antenna socket.
> > Just disconnecting it from my 590, and connecting straight to the
> > antenna doesn't change things. I thought it might be something
> > generated inside the TS-590 where it acts as a second receiver cum
> > panadaptor. Will try what you suggest next time, but suspect it's
> > actually pulling this from the air waves round here.
> >
>

I also figured out that using a poor audio cable [from rxtx to soundcard] for
the input from the rxtx to soundcard will cause a problem. I replaced both tx
and rx 3.5m audio cables, and it really cleaned up my panadapter.

73's

--- In softrock40@yahoogroups.com, "edingraham" <edingraham@...> wrote:
>
> When operating at Full Speed, USB sends a Start Of Frame each millisecond.
With light buss traffic (and poor USB shielding) this might be visible. Try a
new USB cable.
>
> 73, Ed WX4S (who is reading USB Complete in his spare moments)
>
> --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
> >
> >
> > ----- Original Message -----
> > Subject: Re: [softrock40] Re: What might be the cause of this HDSDR display
please?
> >
> >
> > >
> > > Yes, it must be local, but what gives exact 1 kHz signals? I have done
> > > nothing at all, the Softrock's been powered up all the time since that
> > > screen shot, here's a current one, same band, all looks fine...
> > >
> >
> > Chris,
> >
> > I think I've seen people say that the USB can cause this. Maybe an
intermittent?
> > But, yes, find out where it is coming in, check local equipment.
> >
> > I'm not sure about Mike's advice to increase gain. I have good results with
that sort of noise floor, maybe you have calibrated
> > HDSDR? If so then leave it. Yes, it is possible to cover up signals not
coming in through the antenna but I'd say get rid of them if
> > you can.
> >
> > 73 Alan G4ZFQ
> >
> > > http://www.chriswilson.tv/hdsdr2.jpg
> > >
> > > Next time it does it I'll disconnect, then ground the antenna socket.
> > > Just disconnecting it from my 590, and connecting straight to the
> > > antenna doesn't change things. I thought it might be something
> > > generated inside the TS-590 where it acts as a second receiver cum
> > > panadaptor. Will try what you suggest next time, but suspect it's
> > > actually pulling this from the air waves round here.
> > >
> >
>

----- Original Message -----
Subject: [softrock40] Re: Softrock Dynamic Range and MDS Redux

Nick,

Is this using 16 or 24 bits?
Your figure relates closely to what has been said to be a practical maximum for
16 bits.
Yes, I'm reopening the question "is it worth using 24 bits with an an unmodified
Softrock?"

And my simple mind is still wondering if the DSP actually can increase the range
by 20dB? My and Warren's  tests seem to show this,
a range of well over 100dB appear to be seen with a 16 bit card.

73 Alan G4ZFQ


>
> I just measured the 2 Tone Dynamic Range of my Softrock Ensemble Rx and Delta
44 sound card.
>
> TEST SETUP
>
> TenTec Delta 580 VFO set to 5057kHz.  Power output +4dBm.
>
> Homebrew VFO set to 5052kHz.  Power output +4dBm.
>
> Two 20dB attenuators at each VFO output.
>
> Homebrew 6dB hybrid combiner.  Power output -22dBm per tone.
>
> Softrock Ensemble Rx.  Delta 44 sound card.  Linrad set with resolution
bandwidth 1kHz.
>
> RESULTS
>
> MDS = -116dBm in 1kHz
>
> Input Intercept = +20dBm
>
> Two Tone Dynamic Range = 2*(20+116)/3 = 91dB in 1kHz
>
>

You guys have cleared up a couple of mysteries for me.

The "RBW" control on HDSDR controls the resolution bandwidth which, I believe,
equates to the FFT bin size. The lower RBW control has a range of 1.5 Hz to
187.5 Hz. If you run this control through its' range you will see the visible
noise floor change over a range of about 20 dB.

The upper RBW control has a range of 0.2 Hz to 187.5 Hz and seems to move the
noise floor a total of about 30 dB. It is easier to see this if you set the
"Avg" control to 128 samples. This smooths out the noise so you can get a good
reading.

The interesting thing is, just as Milt and Tony described, the noise floor moves
but a single frequency tone signal level does not. This is a great demonstration
of the visible noise floor being the result of different time samples in the
FFT. The longer the sample size, the higher the value.

What does this do for you? As you reduce the RBW value the noise floor drops and
you can see signals that are actually inaudible. Very cool!

At its' highest value, 187.5 Hz, the visible noise floor closely correlates to
the ARRL MDS measurement.

Wonder of all wonders...... this stuff is starting to make sense!

Warren Allgyer - W8TOD

--- In softrock40@yahoogroups.com, Milt Cram <w8nue@...> wrote:
>
> On 2/18/2013 3:43 PM, warrenallgyer wrote:
> > Thank you Milt and Tony! A wonderful explanation of the phenomenon I have
been observing.
> >
> > My follow-on question would be: Could we incorporate the spectral noise
level on the FFT display into the calculations of MDS and dynamic range and, if
so, how?
> >
> > Warren Allgyer - W8TOD
> >
> >
> Hi Guys,
>
> Re: Minimum Detectable Signal and Minimum Discernable Signal
> If you haven't already read this--take a look.
>
> http://www.ittc.ku.edu/~jstiles/622/handouts/Minimum%20Detectable%20Signal.pdf
>
> Milt
> W8NUE
>

--- In softrock40@yahoogroups.com, Milt Cram <w8nue@...> wrote:

>
> In summary--don't be confused by the spectral display when considering SNR,
MDS, and dynamic range.
>
> My 2 cents--

Well said Milt!

> ----- Original Message -----
> Subject: [softrock40] Re: Softrock Dynamic Range and MDS Redux

> > I just measured the 2 Tone Dynamic Range of my Softrock Ensemble Rx and
Delta 44 sound card.

> > MDS = -116dBm in 1kHz
> >
> > Input Intercept = +20dBm
> >
> > Two Tone Dynamic Range = 2*(20+116)/3 = 91dB in 1kHz

--- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:

> Nick,
>
> Is this using 16 or 24 bits?
> Your figure relates closely to what has been said to be a practical maximum
for 16 bits.

It's a standard Delta 44 so I would say 16 bits.

Agree the MDS is probably sound card limited.

> Yes, I'm reopening the question "is it worth using 24 bits with an an
unmodified Softrock?"

Maybe, if you have been measuring over 100dB SFDR.

Have you found a way to measure the Ensemble's MDS independent of a soundcard?

> And my simple mind is still wondering if the DSP actually can increase the
range by 20dB? My and Warren's  tests seem to show this,
> a range of well over 100dB appear to be seen with a 16 bit card.
>

I'd be interested to see the results of your tests Alan.

Does my input intercept measurement make sense to you?

73

Nick G3VNC

This item has been sold.

--- In softrock40@yahoogroups.com, "ansjones" <ansjones@...> wrote:
>
> I purchased a Built SoftRock RX Ensemble II Receiver Kit from FiveDashInc in
December 2012. This kit was built by FiveDash when they still offered Built kits
on their web site. Soon after I purchased the Softrock I also purchased a
FLEX-1500 and therfore I no longer have any need for the Softrock. I paid around
$90 for the Built kit, but would be willing to sell for $60 including shipping.
Please send me an e-mail directy if interested. I can accept PayPal payments.
>
> Andrew J
>

--- In softrock40@yahoogroups.com, "g3vnc" <g3vnc@...> wrote:
> > > I just measured the 2 Tone Dynamic Range of my Softrock Ensemble Rx and
Delta 44 sound card.
>
> > > MDS = -116dBm in 1kHz
> > >
> > > Input Intercept = +20dBm
> > >
> > > Two Tone Dynamic Range = 2*(20+116)/3 = 91dB in 1kHz
>

>
> Does my input intercept measurement make sense to you?

Hi Nick,

I found my tests on the RX Ensemble that I did a couple of years ago and put it
in the files section under my call KF4BQ.  I usually follow ARRL test procedure
(avail on web) for making comparisons with other equipment on ARRL or Sherwood.

Test were with EMU1212M (24bit).
My MDS on 20M @500Hz BW = -131dBm
My IP3 = +20dBm (20KHz spac, S5 IMD level)

The EMU1212M has the great A/D that is used on the SDRWidget and Flex5000 and
easily beats out my Edirol FA66 and EMU0202.

73,  Mike Collins   KF4BQ