Hi Joe, Paul, VLF,
Congrats to the first message CA -> UK on 8.27 kHz!!! A good day for VLF
amateur radio!
Am 22.10.2017 23:43, schrieb [email protected]:
The notebook running SL to generate the carrier doesn't have ntp
But this is necessary when using PPS only! You were lucky, obviously the
PC clock was not drifting to much during the transmission time.
Otherwise there would have been a phase glitch. I suggest to instatt a
ntp client there to avoid the loss of a message or carrier.
2300 utc 22 Oct, 3 characters, 55 second symbols, 8K25A, 8.2700075 kHz.
repeating every 12 hours.
The CRC was missed. But Paul seems to guess it right :-)
8K25 or 16K25 are the most effective modes but the RX station must have
much much RAM to be able to decode it. I have a PC with 16 GB RAM and
actually decode 3 characters in 8K25A but it is the absolute limit :-)
Better is 16K21A, then we all have a chance to decode your messages.
I would be very interested to receive a message from you. Stacking will
be required. If Paul gets 3 dB Eb/N0 then i don't need to try to get a
decode. Several days will be required, maybe.
Would you like to try another 3 character message and repeat it each
night until there is a decode here? I bet that DL0AO is very interested
as well :-)
I am glad you like my new frequency Stefan.
Yes, a good choice. I can move the spectrogram in Cumiana if you like.
Using the 20m high wire would be a great step forward :-)
Please do post the SL-EbNaut file and info on how to use it.
OK, in attachment.
It is based on the settings programmed by DF6NM and has additional
features.
The operation is done from the schedules actions table. Calibration
settings are done in the conditional table.
It calculates the antenna current from the signal level on the input. I
suggest to build a pure capacitive probe to catch a bit of your radiated
VLF signal. Just use a simple wire near the transmit antenne. Even if
the antenna is in 100m distance it should work, you just need a longer
wire. Make sure the wire is mounted in a reagion that doesn't change all
the time, i.e. no people passing by to close to it or no branches of a
tree to close to it. A pure capacitive divider. Think about the 100 pF/m
from a RG58/RG174 feed line...
There is a scaling factor for the antenna current which must be
corrected by you, currently it is 1930. It is in the formula s=factor*...
Then there is a minimum level in dB of that feedback signal, in line 3
and 4 or the conditional actions. Currently it is set to -40 dB. That
means your feedback signal has to be above -40 dB to be phase corrected.
Make sure the level is high enough.
Then there are further parameters. alc=1 means that SpecLab hold your
antenna current constant. If the resonance of the antenna is detuned,
the AF output level will change within certain limits and tries to keep
the antenna current constant. This has some advantages, for example it
can help to protect your coil! If your actual resonance is say 30 Hz
above 8270 Hz and rain starts to fall, it will drop to 8270 Hz. This can
cause an increase of the antenna current, depending on the Q of the
system. So it will increase the antenna voltage and could destroy your
coil. The ALC regulation is quite slow, which is good, because there is
another function, the safe function.
safe=1 means that the transmission will be stopped if the actual antenna
current suddenly drops below a certain limit. The limit is the parameter
L and the target antenna current is the parameter d. If you want to run
300 mA antenna current, set d=300. If you think it will stay constant,
set L=30 for example. If something happens, maybe your coil drops at
night and would eventualy catch fire you will have a problem, or at
least the coil! When it drops, the resonance will be detuned, the
antenna current drops below 270 mA. The ALC function is to slow to
compensate that. Each 200 ms, there is a check of the antenna current.
If the actual current falls more than L mA below d, then a counter is
incremented. If the counter value exceeds 5, the signal output will be
stopped. So it takes just 1 second to stop the transmission when the
coil drops. This can prevent you a lot of trouble and let you sleep
better!!!
Another parameter c defines the start value of the ALC. It makes sense
to choose a small value like 0.4, then start the transmission, choose
alc=1, wait until the target current is reached, read the new value of
it (just by moving the mouse onto the character c in the conditional
actions table and read the text field) and then change the start value
of c (in the scheduled actions table) to that value, or slightly lower.
When you start a transmission automatically, the start current will then
be quite close to the target current.
There are further fuctions that are maybe self explaining...
It appears to be complex but actually it isn't :-) I'm using it daily :-)
Still open questions?
73, Stefan
SETTING8.zip
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