VLF,
Here is an overview of my last transmissions on 6470 Hz and some
notes/thoughts about the recent work.
The 1 character day time message, as announced, was running from the
12th to 14th.
I tried to get a decode from the 12th, 13th and 12th+13th from the
RC4HAA RX site, but without success. Yesterday the remote access was not
possible but their grabber is running, so there will be a last chance
soon to stack 12+13+14.
There have been a number of false decodes with good Eb/N0, so i conclude
that a 1 character message with 0 CRC in 8K19A is not really a good
choice because the number of symbols is so low and this makes false
decodes that appear to be correct more likely (?)
Some CRC seems to be necessary in any message, although 'it hurts' in
short messages because it quickly becomes a significant part of the
overall symbols, or in other words, the symbol length must be choosen
significantly shorter when the transmission time is fixed (fixed because
there is always an open time window for a daytime or nighttime message).
Comments welcome.
Did someone else try to get a decode from the 3 stacked or individual
messages?
The 16 character night time transmission, as announced, was running each
night since the 5th. It was completed this morning 4 UTC, for the 10th
time! RN3AUS told me he want to visit his garden tomorrow morning to
take the recorded files. Then we can try a last attempt to get a decode
by stacking all messages. Thus i decide to run the message a 11th time
this night, because the QRN has been much lower in the last days again.
If we can't find a decode with the Windows decoder, we will provide the
11 wav files to Paul, so he could help us getting the message, or at
least to find out what happened, why i didn't decode.
Right now the transmitter is OFF, quite unusual meanwhile :-)
If we can't get a decode from the 16 character message in 1985 km
distance, i would like to try shorter messages, until we got some
success! So far, if i remember correctly, the longest message on 6470 Hz
over that distance is 2 characters, so this could/must be beaten!
I got a new email from RC4HAA, they want to put somemore effort in
generating a proper PPS pulse to get better results and a stable phase
on the RX. But i don't know when this will be completed.
A last set of experiments on 6470 Hz will be started soon: Transmitting
on two different frequencies, 6430.005 Hz and 6510.005 Hz. I managed to
run 200 mA on each frequency, simultaneously, with the same
antenna/coil/PA. The phase of each frequency as well as the antenna
current can be kept constant! So maybe we can see some propagation
effects on different locations. Is someone interested to take part?
After that, i intend to go to 8270 Hz with maximum antenna current (700
mA) for a short time to leave a trace at RC4HAA. Then i will move to
5170 Hz finally...
73, Stefan
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