Re: LF: More EbNaut 137.777

[jcraig@mun.ca]

Paul,

The exciter quit sometime during the night.  Perhaps around 0400! 
Nice numbers for 50 watts and poor timing on my end!
I know someone who might have a source of  GPS PPS to correct 
this problem.
The RasPi is sitting on the desk -- It may make a nice VLF RX.
Is a sound card required to use your VLF RX software?

The Arduino may have slow oscillator.  I could clock it with a
DDS that is clocked with the DOCXO or try your idea with the
RasPi. Another problem could be sloppy programming. I have
to comment out the statement calling the EnNaut symbol array if
opertion on CW or OPERA is needed!

73 Joe

On Thu, 26 Nov 2015, Paul Nicholson wrote:

> Final result
>
> time   Eb/N0     T-Offset  Phase
> 00:00  no decode, tried very hard
> 00:30  -0.8 dB    +1.8   -30  -60  -60  -90 (rank 35975 BER 36.8%)
> 01:00  10.8 dB    +2.9     0    0   30   30
> 01:30   8.4 dB    +4.2   -90  -90  -60  -60
> 02:00   9.7 dB    +5.7   -30  -30    0    0
> 02:30   8.0 dB    +6.7    180  180 -150 -150
> 03:00  11.6 dB    +7.9    180  180 -150 -150
> 03:30  12.4 dB    +9.1     0    0  30    30
> 04:00  no decode
>
> Most phase patterns show a slight increase in phase lead,
> so the frequency is a bit higher than 137.777000 this time.
>
> Wonder what happened to the signal before 01:00, it was very
> weak, 00:30 was right on the limit.
>
> Joe I hope you can fix the Arduino clock.  Is it losing RTC
> interrupts or something?  Or just a slow xtal?  Do you have a
> Raspberry Pi?  I can quickly put together a keyer program.
> It would be fun to do a really weak signal test with longer
> symbols but the clock will drift too much by the end of the
> message.
>
> Markus wrote:
>
> > Actually, each station operator is using his own
> > unique home-grown setup:
> That's a wonderful summary, thanks.  W4DEX and other
> VLF stations could also go on the list too.
>
> Various mentions of previous experiments with coherent signals.
> I've been following those up and found some interesting reading
> and good results.  But coherent operation never caught on for
> some reason.  Maybe too fiddly and expensive?   We're lucky
> today because PCs are better and GPSDOs only cost a day's
> wages not a month's.
>
> I'm enjoying dabbling with this and it revives my interest
> in amateur radio.  Hopefully we see a few more stations adding
> themselves to Markus' list.
>
> --
> Paul Nicholson
> --