Several weeks ago I mentioned on this reflector that I was
thinking about ways to better integrate the combined use of
Linrad and WSJT. I write now to bring you up to date on my
progress.
In my 2-meter EME station I use the Antennspecialisten WSE
converters with a Delta 44 sound card and a small 2x10 xpol
antenna system. Therefore I have full polarization
information and about 90 kHz of usable bandwidth on 2 meters.
I have inserted code into Linrad that taps off Linrad's
time-domain data as it flows into the "fft2" processing
stage. At this point the full received bandwidth and
polarization information is still available, and noise
blanking has already taken place.
The data stream from Linrad is divided into one-minute
blocks corresponding to each UTC minute. These blocks
(about 46 MB each) are sent to a separate program that I
have tentatively named MAP65. MAP65 runs in the background,
and is assigned a lower priority than Linrad.
When a full minute of data is available, MAP65 scans the
full 90 kHz (or any designated portion) looking for JT65
signals, which are easily recognized by the software because
of the known pseudo-random pattern of their sync tones. For
each detected JT65 signal, the program "peaks up" to find
the best-fit values of frequency, time delay DT, and linear
polarization angle. It then decodes the received message.
The results are displayed in the form of a "band map" that
looks something like the following (based on a particular
segment of recorded data that I have been using for tests):
Freq DF DT UTC Seq Message KV DS
-----------------------------------------------------------
144.114 -4 2.6 1753 2 # WA4EWV RK3FG KO86 OOO 1 0
144.127 340 2.7 1753 2 * CQ KB8RQ EM79 1 10
144.129 204 2.7 1753 2 * QRZ W5UN EM23 1 0
144.131 234 2.6 1754 1 * CQ S52LM JN65 1 10
144.133 -281 2.7 1754 1 * CQ 9H1TX JM75 1 10
144.145 -14 0.3 1753 2 * OK1TEH K5GMX FN31 1 0
144.147 -250 2.7 1754 1 * CQ EA2AGZ IN91 1 10
The band map presents a list showing the most recent decoded
message at each frequency containing a JT65 signal. The
list is sorted in order of increasing frequency, and is
updated every minute; at a given frequency (within a
specified tolerance) only the most recent decoded message is
shown. With some effort put into a user interface, decoding
histories at each frequency cold be made available optionally.
MAP65 is still very much in development, but all of its
essentials are in place and working well. The program
automatically finds and decodes all detectable JT65 signals
in a 90 kHz slice of a band -- and it does this in well
under a minute, so that it can keep up in real time.
Sensitivity is the same as that afforded by WSJT for a
single received signal.
By watching the band map I can see at a glance who is on the
air, and who they are working. During a contest, I could
easily find the station I want to work next.
So far, I have tested the program only using 15-minute
segments of data recorded several weeks ago using Linrad's
'S' command. Real-time tests have yet to me made -- and
they will now have to wait for completion of an antenna
upgrading project at my station. Last week I took down my
pair of 2MXP20 yagis, and I am temporarily off the air for EME.
I would appreciate any feedback or suggestions from other
users or potential users of Linrad and JT65. Based on this
brief description of MAP65, would you use such a Linrad
add-on if it were made available? If so, what else would
you want it to do?
With best wishes,
-- 73, Joe, K1JT
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