Message-ID: <509299E8.7010608@princeton.edu>
Date: Thu, 01 Nov 2012 11:48:56 -0400
From: Joe Taylor <joe@Princeton.EDU>
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:8.0) Gecko/20111105 Thunderbird/8.0
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
CC: rsgb_lf_group@yahoogroups.co.uk
References: <508D92BE.2040500@broadpark.no> <508ED047.1000504@broadpark.no> <CAHAQVWPFQdJQxMtkvzOvGZ-SbzGk3WTptmvMqDzBqpECjzjpgQ@mail.gmail.com> <508EEDA9.7070905@princeton.edu> <50901CB0.2040405@princeton.edu> <50917D09.2030908@princeton.edu>
In-Reply-To: <50917D09.2030908@princeton.edu>
Subject: LF: Soundcard issues
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


No AC power at home, yet.  My wife and I are essentially camping out, at 
home.  We have plenty of firewood and a good fireplace, but we are 
bored.  As you will have heard, we are among the lucky ones.

I am writing this message, once again, from my university office.

A few words for those reporting "too much audio" on input to WSJT-X.

On my development system the same input level is required to make both 
WSPR and WSJT-X happy.  Likewise on my shack computer.  For example, see 
the screen shot posted at
http://physics.princeton.edu/pulsar/K1JT/WSJTX_WSPR.png

Could it be that those who report having to move audio level sliders far 
downward are using 24-bit soundcards, and their drivers are sending the 
low 16 bits (via portaudio) to WSJT-X?  I do not presently have another 
explanation.  I do not find any level discrepancies here.  Obviously, I 
cannot test hardware I do not have access to.

Perhaps I should put in a digital attenuator to handle this issue?

On a possibly related matter: I am aware that a wide variety of hardware 
is being used to generate and receive signals on our MF and LF bands. 
In due course it may be desirable for WSJT-X to use 48 kHz sample rate 
for input, as well as output -- and even to offer I/Q input and output 
for direct-conversion rigs.  These features have been in WSPR 3.0 for a 
long time, and they work well.  If there is sufficient demand they could 
be introduced in WSJT-X as well.

At present, my available time is being spend on the JT9 decoder.  With 
well-behaved signals and a clean noise background, the JT9 threshold 
decoding sensitivities are those given in a table at the end of the 
Quick-Start User's Guide,
http://www.physics.princeton.edu/pulsar/K1JT/WSJT-X_Users_Guide.pdf .

JT9 performance may be degraded in the presence of QRM, static crashes, 
plasma TV birdies, frequency drift, etc.  Extensive experience with JT65 
on both EME and HF paths shows that most of these annoyances can be 
minimized or eliminated by suitable optimizations in the receiving 
software.  These optimizations have not yet been started, in part 
because I do not yet have suitable examples of *.wav files recorded in 
difficult receiving situations.

Nobody has yet sent me a file that, when opened, produces the result 
"15P6715P67WCV".

Maybe we'll have power again by tomorrow?  Or maybe not.

	-- 73, Joe, K1JT