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Thanks very much Marco and Terry for trying, and to
Klaus DJ6LB who sent a nice recording from 20 km. I have stopped
transmitting at 13:50 due to onsetting rain, but may resume an hour later
if the weather lets me.
Terry the slow-voice stuff still needs a litte more
work. I will be happy to share it once it runs a bit more reliably. And despite
my scepticism, I would indeed be interested to team up with Geri and
others to try FreeDV on low bands.
Best 73,
Markus (DF6NM)
----- Original Message -----
Sent: Sunday, January 06, 2013 2:54
PM
Subject: RE: Bandlimited SSB test on 136
kHz
Hi
Markus
I
am always interested in new communications experiments!
I
listened for your test transmission at 13:30 but, unfortunately, heard nothing.
I’ve used my SDR-IQ to record the spectrum so I can analyse off-line in more
detail later.
Although
I am not yet in a position to Tx on 136 kHz, I will try to monitor your
slow SSB tests if you would like to make the software
available.
I
know you do not fancy using DV but just to mention that I have had some success
(on HF) with FreeDV. This uses a recently developed opensource CODEC and
has an 1100 Hz BW.
73
and GL with the tests.
Terry
GW0EZY
----- Original Message -----
Sent: Sunday, January 06, 2013 2:45
PM
Subject: LF: Re: Re: Bandlimited SSB test
on 136 kHz
Sorry Markus...
I see from your grabber that you started.. but
nothing here to hear..just a steady tone on 137.5
will qsy back on 472 wspr (rx only!)
73 de Marco, IK1HSS
----- Original Message -----
Sent: Sunday, January 06, 2013 1:06
PM
Subject: LF: Re: Bandlimited SSB test
on 136 kHz
Hi Markus,
stucked of bad cnd on 472 (Stefan arrives
irregularly with -30 dB S/N....) I'm now in rx usb on 136
GL
73 Marco, IK1HSS
----- Original Message -----
Sent: Sunday, January 06, 2013 12:50
PM
Subject: LF: Bandlimited SSB test on
136 kHz
Dear LF,
around midday I have
been conducting some test transmissions using 136.0 kHz USB
voice. To comply with German regulations, the audio spectrum has
been cut off sharply below 300 Hz and above 1100 kHz, occupying
136.3 to 137.1 kHz RF. Despite this rather mediocre speech
quality, it is still possible to hear the voice and copy a
simple message.
To my surprise, the speech was quite
audible on the Twente WebSDR (434 km), squeezed between the
bursts of DCF and HGA. There's a recording and screenshot at
Of course it does get boring speaking only to
myself ;-). If you'd like to listen yourself, I intend to do another test
transmission starting 13:30 this afternoon. As the audio is realtime
and standard SSB (apart from the filtering), no software postprocessing is
needed..
Slow voice transmission (ie
the audio deceleration/acceleration method originally used by DK8KW
and myself) would be nicer as it can fit a full SSB channel into
800 Hz. I have been working on a semi-automatic control,
with a fixed one minute raster similar to JT9-1. This will hopefully
allow us to comfortably exchange one 20 second voice message per time slot
(speak during seconds 0 to 20, concurrent
transmit and receive at 1/3 speed from 0 to 60,
replay starting 40 to 60). Anyone interested?
Best 73,
Markus (DF6NM)
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