VLF,
Yesterday in the night i tried some further tests on VLF,
Dreamers-Band, 8970 Hz, using the WOLF 10 mode. An active E
field probe was used on my home QTH which is 950 m distant to
my work, where the fixed antenna (used for LF) was used to transmit on.
That's not really a remarkable DX, not even in the far field. Anyway,
it was fun and keeps me promising.
In contrast to the usual VLF work that is done from local fixed
antennas, where "only" a few dashes are visible on the grabbers, i hope
to cover some distance with this mode, where a full call and locator
and something like 73, 55, CU, GL, TU... can be sent. In contrast to
e.g. WSPR, what was reported to be about as "good" as QRSS-3 i want to
give this mode a chance on VLF, as an exception. Maybe it helps me a
bit to understand why so many LFers like the data modes, hi. ;-)
The receive site in the yesterdays test showed a quite good spectrum!
To my surprise there is much less QRM at home. Here is a photo which
shows the wideband situation during the test using the WOLF10 mode:
http://dl.dropbox.com/u/19882028/VLF/Wideband%20at%20home%20in%203Hz%20FFT%20bin%20width.png
The TX was the LOPT driven by a more than suboptimal working class AB
PA. The output voltage didn't really look like a sine wave but seemed
to contain the wanted spectrum as well ;-) The PA took about 3 W input
power and the PA efficiency must have been terrible. But the results
were fine and so its worth (for me) to optimise things to gain at least
10 dB output power.
The signal wasn't visible in the WOLF gui spectrogram. Since its a
spread spectrum it may not be useful to try to display it in QRSS-60 or
slower.
The first decode appeared after about 6 minutes.
2012-02-01 23:26:43 >WOLF10 -r 22050 -f 8970 -t 0.3 -w
0.0000 -ut
23:27:07 f: 0.175 a:-0.9 dp: 73.4 ci: 3 cj: 66 LTEA6I*44POZVOC ?
23:27:31 f: 0.180 a:-1.1 dp: 69.2 ci: 4 cj:469 AESB3A64IHMY91V ?
23:28:19 f: 0.176 a:-0.9 dp: 66.5 ci: 0 cj:348 XETAVDCFKFJ/6ZL ?
23:29:55 f: 0.273 pm:1.216 jm:407 q:-13.2 -8.6 TFVIM68HW6GXMMB ?
23:31:31 f:-0.127 pm:2.044 jm:741 q: -5.4 -6.2 71DU8HVLDJN49IK -
23:33:07 f:-0.127 pm:3.457 jm:741 q: -4.3 -5.2 73 DK7FC JN49IK -
23:34:43 f:-0.127 pm:5.364 jm:741 q: -3.0 -3.5 73 DK7FC JN49IK -
23:36:19 f:-0.127 pm:5.745 jm:741 q: -1.8 -2.3 73 DK7FC JN49IK -
23:37:55 f:-0.127 pm:6.250 jm:741 q: -0.9 -1.6 73 DK7FC JN49IK -
23:39:31 f:-0.127 pm:7.205 jm:741 q: -0.2 -1.3 73 DK7FC JN49IK -
Then i've done several tests using different frequency tolerance values
(above: t = 0.3 Hz). After calibrating the soundcard by using the shown
offset, the offset was 0, consequencial ;-) But even if a tolerance of
0.002 Hz was choosen, it still took about the same time to get
the first decode. Any comments?
2012-02-02 01:33:16 >WOLF10 -r 22050.222 -f 8970 -t 0.002
-w 0.0000 -ut
01:33:40 f: 0.005 a: 1.6 dp: 70.7 ci: 3 cj:391 U3K6J06JK76C6J0 ?
01:34:04 f: 0.002 a:-1.5 dp: 67.0 ci: 2 cj:395 0V*9CNF9T3VME9V ?
01:34:52 f:-0.001 a:-1.4 dp: 62.8 ci:13 cj:151 N9KZRESEV9.EUHJ -
01:36:28 f: 0.000 pm:1.159 jm:659 q: -6.8 -8.5 3DZ037H*TFCZL10 ?
01:38:04 f: 0.000 pm:2.101 jm:659 q: -4.7 -5.1 73 DK7FC JN49IK -
01:39:40 f: 0.000 pm:2.699 jm:659 q: -5.1 -3.8 73 DK7FC JN49IK -
01:41:16 f: 0.000 pm:3.896 jm:659 q: -3.4 -2.4 73 DK7FC JN49IK -
Currently the PA has problems with self oscillations that even seem to
be present when there is a input signal. But sometimes the self
oscillations were OFF. During this time the signal was visible in the
spectrogram. So i am optimistic to cover much more distance as soon as
the PA works as intended.
I want to ask the experts which S/N imrpovements can be expected when
using the WOLF 5 or WOLF 2.5 mode? Is it 3 dB respectively 6 dB?
Right now i feeld that i am missing a spectrogram which i can show
here. Just text! Odd.
73, Stefan/DK7FC
Am 01.02.2012 15:05, schrieb Stefan Schäfer:
Yesterday i decided to build a quick class-AB "linear" mode PA to drive
the LOPT for a local test which i will do in some hours. My first test
to propagate and receive a WOLF 10 VLF signal over a distance of 950m,
http://dl.dropbox.com/u/19882028/VLF/WOLF%20VLF%201st%20test.png
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