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Fwd: [linrad] Fw: Linrad-01.03



Hello,

I have several comments.

First, I am somewhat non-plussed at the trouble you had with RHL.  Multiple versions
of Linrad have worked with well here with versions of RHL from 6.0 thru 8.0,
including 7.x.  And I have used the Delta44 [along with various soundblaster cards
for the output] with each of these versions with good results.

Now to the specific issue.  I have several questions:

1.  Are you using Linrad with a homebrew front end?  If so, what is the bandwidth
that you are feeding into the Delta44?  If you are running Linrad from the audio
output of another receiver, the Linrad bandwidth and frequency response will be
limited by the audio bandwidth of the receiver.

2.  What soundcard are you using for the output of Linrad?  You really should be
using the Delta44 as input and another soundcard as output so your input and output
sampling rates do not have to be the same.

You have full graphical control over the filter bandwidth with Linrad.  You go to the
baseband window and just pull the filter width to be what you want with the mouse. 
If there is not enough bandwidth in the baseband window then you can use the arrows
at the top of that window to increase the bandwidth so that you have enough.  

You change the BFO frequency by pulling on one of the 3 sets of horizontal bars on
the baseband window.  One side gives you USB, the other LSB.

All of this is explained nicely on Leif's pages, or in a DUBUS reprint that is on one
of my webpages at:

http://www.qsl.net/w3sz/DUBUSLinrad2002.pdf
http://www.qsl.net/w3sz/i3dlifinal.png is the color figure for the article.
These are referenced at http://www.qsl.net/w3sz/start.htm 

Here is the relevant text from that article:

To the right of the high resolution display, on top, is the baseband display. In the
baseband window you can see that I3DLIís s ignal is nicely centered in a 25 Hz
bandwidth filter. The line and Ďhumpí or inverted ĎUí (yellow when you can
see the
colors) in the baseband display show the filter center frequency, bandwidth, and
shape
factor in graphical form. If you want a different filter bandwidth or shape factor,
you just take the mouse over to the baseband display, and drag the filter curve wider
or narrower, and the filter adjusts graphically. THIS REALLY WORKS!! On this display
you can see both the center of I3DLIís signal and the keying sidebands within the
yellow outline of the filter band pass curve. There are several controls in the
baseband window. As we
just noted, by dragging the yellow lines with the mouse you can set the filter width
and
shape factor. There is a red horizontal bar at the left of the window that does not
really
show up with grayscale reproduction. This is the level or volume control and it is
adjusted by clicking it or dragging it with the mouse. Above it is a very bright red
Ďdotí
(actually a short, horizontal line) that indicates the received signal level. It is
Ďpinnedí at the top of the scale, commensurate with I3DLIís usually excellent
signal strength. The fact that this is red indicates that I3DLIís sig nal is so
strong that the audio channel has saturated with the selected audio gain level.
Reducing the gain will cause this dot to become white in color and to fall below the
top of the graph. There are three red vertical bars on the left of the window that
are the BFO controls. You can vary the pitch of the received signal without taking it
out of the filter pass band or moving it in the display by dragging one of these
three bars. The upper bar represents the true BFO frequency. With the expanded
frequency scale it is actually far outside the window and therefore cannot be used to
set the desired pitch. The lower bars have the frequency scale of the BFO frequency
offset contracted by 10 and 100 times respectively, so that at least one control will
always remain in the window and be available to set the BFO frequency.

Hope that helps.

Reply if questions.

73,

Roger
W3SZ





> I finally have linrad up and going, I think. At least I can hear beacon 
here 
> on 6 meters. I am feeding the audio out from linrad to the audio card 
input 
> on a second computer sound card, which feeds WSJT mode FSK441. I note that 
I 
> get a narrow band signal at about 500 hz. How can I widen the output to 
> cover about 2400 hz centered on 1550 hz ? 
> I am using SUSE 8.0 and OSS with Delta 44 sound card. It has been a real 
> struggle to get Linrad to work. I gave up on Redhat 7.1 and switched to 
SUSE 
> 8.0. 
> 




73,
Roger Rehr
W3SZ
FN20ah
http://www.qsl.net/w3sz


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