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I should add
The MF / EME and 8Khz
AUDIO-BAND modes are not Spread Spectrum as
defined by the FCC , and are similar to CMSK
in deploying a direct sequencing engine , the
expected lowering of the minimum detection threshold
,subsequently may be observed in both modes,
Reference may be made to
this months Rad-Com Magazine Data coms article ,
by Andy ...
G..
Sent: Sunday, October 02, 2011 12:19 PM
Subject: LF: A test of cmsk on 8.97kHz
For those who
can, the ROS direct drive 8 Khz sound
card based system , with optional X2
Tx frequency to compensate for class e/d
divide by 2 , is still available
for use ,
details at :-
__________________________________________________________________________________________________________
A test of cmsk on 8.97kHz
Hi
all,
The last few days I've been doing some digi mode testing at 8.97
khz;
"dreamers band", mostly with use of the QRSS mode.
On the
transmitter side, I have been using a 5 turn 10 x 10 m antenna
and an audio
amplifier 100W. The system is feeded with a signal from the
program "Spectrum
Lab".
On the receiver side, I have been using a 70 x 70 cm 60 turns
loop,
tuned with a capacitor. The loop was connected to the microphone
input
on my laptop and decoded with "Spectrum Lab".
The result has
been interesting . With this simple arrangement, I have
reach a distance of
2.5 km.
Yesterday I tried out CMSK8 made by ZL1BPU Murray. I had to make
some
changes in the ini-file to get the CMSK work om 8.97khz. The
sampling
rate was adjusted with the program CheckSR and the
transmitting
frequency was set to 8970Hz. Waterfall has a 2000Hz limit so
this was
black and useless on 8790Hz.
It would makes it easier to
track the signal if the developer could
extend waterfall to 10 kHz. Iam aware
that one can get the view of the
waterfall by going down in frequency, but
8.97khz has become a de facto
water hole of VLF .
The result was
exciting. A clean copy of the signal was received at
about 2 km.
I
would also try to test out some of the VLF mode in multipsk ,
especially
PSK10 and PSKAM10, but I have not find a way to fool the
program to work on
8.97Khz yet.
73 and good dx the VLF Steinar
la5vna
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