[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[linrad] Re: MAP65 and Linrad Network
- Subject: [linrad] Re: MAP65 and Linrad Network
- From: Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>
- Date: Fri, 22 Jun 2007 20:16:47 -0400
One of the nuisances of using the original data file is that
Linrad's raw data are not time-stamped.
Oooh! But they are:-) Your file is stamped 1163231107.413487 which
was the output of the routine current_time() at the start of
FB! This is good to know.
I do not know how to interpret the MAP65 screen. The polarisation
data of AA1YN seems odd to me. They change very rapidly:
The MAP65 screen shot on my web page
http://physics.princeton.edu/pulsar/K1JT/MAP65_1.JPG is from a
very early version of the program. Polarization information
shown for AA1YN in the main text window is incorrect, but you
can find the correct data in the window at lower right. In that
panel the columns of numbers are frequency in kHz (above 144.000
MHz), additional frequency increment "DF" in Hz, polarization
angle in degrees, and UTC. For AA1YN, therefore, the measured
polarization angles over this block of time were
In normal operation with a fully working MAP65, the main text
window is used for the current QSO. New text appears there at
about t=55 seconds in the receive interval. Decoding of the
remainder of the bandpass takes place subsequently, and on my
development computer finishes at about t=12 s into the next minute.
Which signal on the screen that has this behaviour is not obvious to me.
The processing screen says Freq 128 and DF=0 (or very close.)
When I look at the file, I find the weak signal at the center of the
lower waterfall to start at 144.129823 and drift down to 144.129814.
JT65 users conventionally use a "quasi-channelized" approach for
specifying frequencies. The frequencies correspond to that of
the suppressed carrier of the generated SSB signal.
Calibrations on the MAp65 screen follow these conventions.
MAP65 reports the "channel frequency" as 144.128, as shown by
the "128" at the beginning of the lines in the main text window
and also in the panel at lower right. Owing to a combination of
Doppler shift and calibration errors, the actual received
frequency was higher by about +222 Hz at 0746 UTC, drifting
slowly downward to +216 Hz at 0758.
The JT65 sync tone is at 1270.5 Hz. MAP65 has also subtracted
330 Hz to correct for an apparent fixed calibration error (at
144.125) in my WSE converters.
Therefore, with normal Linrad calibration you should expect to
see the AA1YN signal at the frequency
144.1298225 at 0746 UTC.
You measured 144.129823 MHz, so we are in almost perfect agreement.
That is a 1.818 Hz frequency shift as compared to the MAP65 screen???
In this case the shift is 1270.5 + 330 + DF = 1822.5 Hz at 0746 UTC.
There is some info "Options" in the upper waterfall, but that does not
In that early version of MAP65, the information there is
The signal at 144.12982 is right hand circular in Linrad and it
does not change polarisation during the 10 minutes.
I don't pay attention to the V (circular) Stokes parameter in
MAP65. However, there seems to be plenty of linear polarization
in the AA1YN signal, certainly enough to establish its angle
pretty well. The linear polarization (major axis of the
ellipse) is at about 70 degrees, perhaps rotating slightly
downward over the 12 minutes.
The strong signal at -880 Hz in the lower waterfall is at 144.12894
in Linrad. This signal is elliptic, about 50% left hand. Polarisation
does not change with time on this signal either.
This big signal is KB8RQ. MAP65 reports the linear polarization
angle to be around 90 degrees, increasing somewhat during the 12
Don't hold me too much to these polarization-angle numbers.
They came from a very early MAP65 version; I was still playing
with the algorithms then, and I don't recall exactly at what
stage the screen-dump was made.
-- Joe, K1JT
This message is sent to you because you are subscribed to
the mailing list <linrad@xxxxxxxxxxxxxxxxxxxxx>.
To unsubscribe, E-mail to: <linrad-off@xxxxxxxxxxxxxxxxxxxxx>
To switch to the DIGEST mode, E-mail to <linrad-digest@xxxxxxxxxxxxxxxxxxxxx>
To switch to the INDEX mode, E-mail to <linrad-index@xxxxxxxxxxxxxxxxxxxxx>
Send administrative queries to <linrad-request@xxxxxxxxxxxxxxxxxxxxx>