[hpsdr] PowerSDR/OpenHPSDR mRX PS v3.2.25 released

[Doug W5WC]

All,

PowerSDR/OpenHPSDR mRX PS v3.2.25 has been released.

This release can be downloaded from the openhpsdr.org website.
http://openhpsdr.org/download.php

This release contains the following changes:

* Further Advancement for NR2.  NR2 has been further enhanced with a new
"Gamma" gain method.  While the change from the previous NR2 is small, this
further advance has been demonstrated to slightly further reduce background
noise and also to reduce certain audio artifacts of the noise reduction
process.  After a database reset, this will become your default gain method
--- so no need to worry about selecting it.

* PureSignal Auto-Attenuate.  One of the more difficult parts of PureSignal
setup has been adjusting the attenuator during TX to optimize performance.
There is now an option (selected by default, on the Linearity window) to set
the attenuator automatically for you.  When PureSignal begins a calibration,
if the attenuator is not set correctly, it will calculate a new value, turn
itself OFF, apply the new value, and turn itself back ON.  In the event that
the initial condition is one of too much attenuation, the new value should
be correctly calculated and applied in a single step.  In the event there is
not enough attenuation and the ADC is in overload, multiple steps may be
required.

* Protection for External Linear Amplifiers.  Some external amplifier
manufacturers caution users that they must connect "ALC" from the amplifier
to the exciter so that the exciter will reduce drive to protect the
amplifier in the event of certain types of faults, e.g., over-current, arc,
high-SWR, etc.  This has not previously been an option with openHPSDR
exciters since no connection has been provided on these exciters.  Clyde,
K2UE, has led a project to develop an appropriate hardware interface for
this.  Software support has been added to enable the use of this interface.
Documentation will soon be posted and the location announced.  While you can
certainly build your own hardware interface from this documentation, also
stay-tuned for a possible future announcement on availability of hardware.

* Workaround for using the Ext1/2/XVTR ports on the rev24 PA board with
receive only antennas. To use a receive only antenna with the 100W ANAN
radios shipped since Feb 2015 you will need to check the "Disable BYPASS"
box located near the bottom of the Setup=>General=>Ant/Filters=>Antenna
page. Please do not use this with previous versions of the PA boards.

* As usual, several bug-fixes and clean-up items.

NR2 - MORE INFORMATION

NR2 has received particularly positive feedback since its introduction a few
weeks ago.  While all noise reduction algorithms tend to have some audio
artifacts, the NR2 algorithm has been reported to be quite effective in
reducing background noise without the tiring sound of typical LMS
algorithms.  Several people have reported that they leave it enabled all the
time.  There have also been a few questions on usage; so, we'll provide some
clarification here.

Activation:  NR2 is selected using the same button as NR.  From the OFF
state, click once to get NR (the normal SDR LMS type algorithm) and click
again to get NR2 (a very different type of algorithm). Clicking a third time
will get you back to the OFF state.

Noise Reduction and AGC:  AGC, if not properly adjusted, is the enemy of
noise reduction algorithms!  The reason is simple - AGC's job is to adjust
gain to bring things to the same level, whether those things are two
different signals or a signal and the noise during the speech pauses.  So,
when NR/NR2 is trying to reduce noise, if AGC is trying to restore it, they
are in conflict.  For proper operation, there are two things to observe:
(1) Set your AGC gain properly, and (2) if you experience AGC-pumping of the
noise level when using NR/NR2, try selecting the "Pre-AGC" use of NR/NR2
rather than having it "Post-AGC".
- AGC gain can most easily be correctly adjusted by displaying the green "G"
line on the panadapter and pulling it up to be a few dB above the noise
floor - experiment and you'll see how it works.  To display the line, see
Setup/DSP/AGC-ALC.  To move it, "grab" the green square at the left side
using your left mouse button.
- To select Pre-AGC, see Setup/DSP/NR-ANF.

Other Settings:  You will note that there are other settings for NR2
available on the Setup/DSP/NR-ANF tab.  I recommend you select "Gamma" 
as the gain-method, either "OSMS" or "MMSE" as the NPE-method, and leave
AE-Filter checked.  These settings match the default settings.  In other
words, there's nothing you need to do here.  On the other hand, if you wish
to experiment, and if you find some different combination that works better
in some special situation, please let us know!  That will be helpful for
future developments.


You WILL need to reset your database for this release.

Thanks & 73,

Doug, W5WC
Warren, NR0V