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P3 display versus FlexRadio

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N7US

P3 display versus FlexRadio

I saw a demo last night of the FlexRadio bandscope. It showed the noise
well above, on the Y-axis, the bottom of the display, but the waterfall
didn't show the noise, just the signals on the band.

When I set the REL LVL on my P3 so the noise floor is below the noise, the
waterfall is blue from the noise, making it difficult to see the signals.

Can someone enlighten me as to why the displays are so different?

73, Jim N7US

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wayne burdick

Re: P3 display versus FlexRadio

Administrator

Hi Jim,

They may be automatically calculating a long-term-average noise floor, then subtracting it from the waterfall. The P3 could do the same thing. But automatic noise subtraction would have the same disadvantage as slow AGC: a temporary rise in the noise floor would mask weak signals for the duration of the averaging time constant.

You can achieve the same thing manually, without the averaging issue. Simply adjust the REF level such that the noise floor is just at or slightly below the line. The waterfall will then be nearly invisible except for signals and higher noise peaks.

Wayne
N6KR

----
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> On May 12, 2018, at 5:54 PM, Jim N7US <[hidden email]> wrote:
>
> I saw a demo last night of the FlexRadio bandscope. It showed the noise
> well above, on the Y-axis, the bottom of the display, but the waterfall
> didn't show the noise, just the signals on the band.
>
>
>
> When I set the REL LVL on my P3 so the noise floor is below the noise, the
> waterfall is blue from the noise, making it difficult to see the signals.
>
>
>
> Can someone enlighten me as to why the displays are so different?
>
>
>
> 73, Jim N7US
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
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Martin Sole-3

Re: P3 display versus FlexRadio

In reply to this post by N7US

I'm not all that familiar with the Flex stuff but in some SDR software
display systems it is possible to adjust the waterfall sensitivity and
contrast independent of any spectrum bandscope position adjustment. It
is often also possible to have any signal levels indicated by such
displays bear no relationship to any accurate level.The P3 waterfall
contrast changes with the reference level setting which in itself
changes with the displayed bandwidth, seems appropriate. Scale will
adjust the sensitivity I think.

In the situation I have here where it is unusual to have any signals on
any band at more than S7-8, nearest centre of any appreciable activity
is several thousand miles away so mostly fairly weak signals, in this
case I find having the waterfall in monochrome, spectrum display is
still in colour, to be quite an advantage. It is quite possible to set
an almost black waterfall with signals barely above the noise floor
showing as grey marks, often much more discernible than anything on the
spectrum display.

Martin, HS0ZED

On 13/05/2018 07:54, Jim N7US wrote:

> I saw a demo last night of the FlexRadio bandscope. It showed the noise
> well above, on the Y-axis, the bottom of the display, but the waterfall
> didn't show the noise, just the signals on the band.
>
>
>
> When I set the REL LVL on my P3 so the noise floor is below the noise, the
> waterfall is blue from the noise, making it difficult to see the signals.
>
>
>
> Can someone enlighten me as to why the displays are so different?
>
>
>
> 73, Jim N7US
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
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Jim Brown-10

Re: P3 display versus FlexRadio

Hi Martin,

I have a somewhat different solution to your problem, and it consists of
multiple parts.

First, I set averaging to maximum (I set it years ago, don't ask me
numbers). :)

Second, I set Scale to 24 dB when I'm not contesting, 32 dB for 100W
contests, 42 dB for high power contests.

Third, I set reference level so that the noise level as at the bottom of
the amplitude display , which causes the waterfall to be black where
there are no signals.

Fourth, I set Tracking Mode ON, so that when I tune, the signals on the
band stay put as I tune across them. Without this setting, Averaging
would reset every time the changes frequency.

A major benefit of averaging is that it causes random noise to cancel
itself out, leaving only signals (and noise that is NOT random). Now,
both the amplitude display and the waterfall will show only real signals
plus noise that's more or less stable in frequency, like clocks from
microprocessors, and "lumps" of noise which may drift a little or a lot.
Those lumps are generated by power-handling devices like switch-mode
power supplies and variable-speed motor controllers.

I don't use monochrome display, but I do see signals against a nearly
black background.

73, Jim K9YC

On 5/12/2018 8:05 PM, Martin Sole wrote:
> In the situation I have here where it is unusual to have any signals
> on any band at more than S7-8, nearest centre of any appreciable
> activity is several thousand miles away so mostly fairly weak signals,
> in this case I find having the waterfall in monochrome, spectrum
> display is still in colour, to be quite an advantage. It is quite
> possible to set an almost black waterfall with signals barely above
> the noise floor showing as grey marks, often much more discernible
> than anything on the spectrum display.

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Vic Rosenthal

Re: P3 display versus FlexRadio

In reply to this post by wayne burdick

This is what I do. Then I read the noise level in dBm from the screen. Very useful to compare noise levels at different times, etc.

But what I would like is a menu command that could be assigned to one of the function keys to automatically compute the average noise level and then adjust the ref level.

There would have to be an adjustment for an offset from the average, so you could set it up once to look the way you like it.

Then you could just tap the key whenever you want to readjust the ref level, and it would alway look the same.

Vic 4X6GP

> On 13 May 2018, at 5:43, Wayne Burdick <[hidden email]> wrote:
>
> Hi Jim,
>
> They may be automatically calculating a long-term-average noise floor, then subtracting it from the waterfall. The P3 could do the same thing. But automatic noise subtraction would have the same disadvantage as slow AGC: a temporary rise in the noise floor would mask weak signals for the duration of the averaging time constant.
>
> You can achieve the same thing manually, without the averaging issue. Simply adjust the REF level such that the noise floor is just at or slightly below the line. The waterfall will then be nearly invisible except for signals and higher noise peaks.
>
> Wayne
> N6KR
>
>
> ----
> http://www.elecraft.com
>
>> On May 12, 2018, at 5:54 PM, Jim N7US <[hidden email]> wrote:
>>
>> I saw a demo last night of the FlexRadio bandscope. It showed the noise
>> well above, on the Y-axis, the bottom of the display, but the waterfall
>> didn't show the noise, just the signals on the band.
>>
>>
>>
>> When I set the REL LVL on my P3 so the noise floor is below the noise, the
>> waterfall is blue from the noise, making it difficult to see the signals.
>>
>>
>>
>> Can someone enlighten me as to why the displays are so different?
>>
>>
>>
>> 73, Jim N7US
>>
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
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