[Lowfer] Spectrum Lab as LORAN receiver

[Stewart Nelson]

John,

Nice picture.  Yes, the identifiers are correct.
Since you can see all the stations in the chain, there is no problem.

In AM mode, it's easy to tell a master, because there is a ninth pulse,
with an extra 1 ms gap.

If only some stations are visible, it is easy to identify them if
the master is seen.  If not, careful measurement of the time
difference(s), taking into account propagation delay, will usually
do the trick.

If only one station shows up, and it is a secondary, it will
be hard to identify.  Try looking at the GRIs used by
the dual-rated secondaries.


Jay,

You can also set the sampling rate using LORAN itself.
In AM mode, using the GRI of your local chain, watch the
pulses slowly drift across the screen.  Suppose that in
one minute, they drift to the right by 1.5 milliseconds.
That means that the actual sample rate is .0015/60 higher
than the current calibration.  So if it was originally at
44100 Hz, set the calibrated value to 44100*(1+(.0015/60)),
which is about 44101.1 .  The drift should now be much less.
If you wish, make a further "fine" adjustment.

If you switch to SSB mode, you can then zero-beat the carrier in
a similar way.  Say it takes 25 seconds for a group of pulses
to go from max, through zero, back up in opposite polarity,
through zero, and back to max.  So you are off by 1/25 = .04 Hz.
I don't know how to tell which way.  Try adding .04 Hz to the
LO frequency, if that makes the beat faster, try subtracting instead.

73,

Stewart KK7KA

> Jay,
> 
> >Did you use the built in SR cal routine?
> 
> Not the automatic routine. Did it manually by feeding in 1kHz from my freq
> std, and entering the numbers in the "Audio Settings" page. Works.
> 
> Here is a screen shot of the NE US chain as seen in the daytime, with the
> loop aimed away from Nantucket:
> http://webpages.charter.net/w1tag/files/NELoran.jpg
> I hope the identifiers are correct.
> 
> John A.