[hpsdr] PSDR stuff

[Warren C. Pratt]

Hi Glen,

Thanks for your inputs.

I'd like to comment specifically on your item number 7 as similar 
comments come up from time to time.

There is a relationship between the noise floor as displayed on the 
S-meter and the noise floor as displayed on the panadapter. However, 
these "noise floors" are two different measurements and depend upon your 
settings.

S-meter:  Measures the noise within the receive bandpass.  So if, for 
example, your receive bandpass is set to 3Khz, you are measuring the 
total noise within that 3Khz.  Furthermore, you have your choice of 
measurement modes for the S-meter - Peak mode (choose "Signal") or 
Average mode (choose "Sig Avg").

Panadapter:  Displays a set of narrow frequency bins across the screen.  
In Setup=>Display/... you can choose FFT size which changes the 
bin-width.  The noise within a very narrow bin is much less than the 
noise within the entire receive bandpass which is displayed by the 
S-meter.  There are also various averaging modes that can be chosen for 
the panadapter.

So, in summary, the noise floor on the panadapter will not agree with 
that shown on the S-meter.  They are measuring different things.  
However, they are both valid measurements.

73,
Warren  NR0V

On 6/17/2015 12:09 PM, MDS Info wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hello,
>
> I have a large list of concerns/suggestions concerning PSDR.  Here a few
> items (one I already talked about)
>
> 1.  There should be a LOCK button for the Pan control.  I would like to keep
> the spectrum as I set it up,
>      regardless of what I click on.  Mine immediately changes the upper and
> lower parts of the spectrum on click.
> 2.  In Alex, there should be a box to allow bypassing the TX LPF in rx mode.
> If there is, mine does not work!
> 3.  In Alex, the XVTR RX does not work.  I have been told it works in
> GNURadio...
> 4.  Using different Hermes boards, each one's calibration is different.
> These values are not saved/restored with the
>      particular MAC address associated with the board.
> 5.  I see no way to set RX2 up differently (LSB vs USB vs CW, etc) than RX1.
> When the 7 receiver version comes
>      along, a separate control panel for the receiver set ups would be
> required, OR the setups must be included
>      in each rx display.
> 6.  With two different Hermes boards, I noticed the same thing.  When I go
> from 15db to 16db of attenuation, the
>      pan adapter display jumps about 4-6db.
> 7.  In the panadapter display, my noise floor is approximately 10db lower
> than the S meter reading with no signals.
> 8.  Often, the noise floor is lower than the maximum -120db setting of the
> AGC line.
> 9.  The squelch control does not seem to function with VAC.
>
> Thanks for listening..
>
> 73's
>
> Glen K4KV
>
>
>
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