Hello Mel,
Hmmm... ok, the use of 14.236 is new to me but I had stumbled on the
digital voice QSO only because of the interference it was causing to a
SSTV QSO. I have two general guesses on what might have been happening:
- I'm pretty sure the station transmitting was using an amp and he
might have been splattering due to over-driving
- This interference might have been a matter of my stock FT950's
2.4Khz roofing filter acts more like a 6Khz filter (not so hot).
Turning on the noise blanker only makes things worse
Considering that not everyone can afford Elecraft K3s and Icom 7600s, I
imagine interference like this will happen to others too. I know this
is like trying to move an elephant but any chances the community can
change their recommendation to move their QSOs up to 14.237?
Respectfully,
--David
KI6ZHD
On 12/23/2012 06:25 PM, Mel Whitten wrote:
Digital voice has been operating on 14.236 since 2007. What I do see
is SSB splatter in your waterfall. The 1+ khz guard channel
between "DRM-based SSTV" and FreeDV FDM is pretty effective
in avoiding interference between the two modes.
Mel
k0pfx
----- Original Message -----
*From:* David Ranch <mailto:[email protected]>
*To:* [email protected]
<mailto:[email protected]>
*Sent:* Sunday, December 23, 2012 6:19 PM
*Subject:* [Freetel-codec2] Trying to decode captured FDMDV +
Codec2 signal
Hello Everyone,
I'm new to the list but I've attended a few of Bruce Peren.'s
Codec2 presentations at the local Pacificon conferences. Much to
my pleasure, I spotted what I think was a FDMDV + Codec2 QSO on
20m today (14.236Mhz). Please note that the transmitting station
was created some splatter that was impacting DRM-based SSTV on
14.233 so I don't think 14.236 is a safe frequency to use).
Anyway, here is a screen capture of the signal as I was receiving it:
http://www.trinityos.com/PRIVATE/Codec2/fdmdv-waterfall-capture.png
I recorded the signal with Fldigi and thought I'd try to decode
it. I downloaded the current FDMDV code as of today from the
Subversion repository and it compiled right up on my Centos6
platform. I then tried the following command to decode the WAV
files but I didn't get any real voice out of it:
sox /tmp/fldigi-codec2-capture.wav -c 1 -r 8k -t raw -s -2 -
| ./fdmdv_demod - - | ./c2dec 1400 - - | aplay -c 1 -r 8000 -t raw
-f S16_LE
I tried many different permutations of the various commands but
couldn't get any speech out of it. Since I'm not sure where the
I posted the two WAV files here:
http://www.trinityos.com/PRIVATE/Codec2/
Could anyone help be confirm this was indeed a FDMDV + Codec2 QSO
and what I might have done wrong?
Ps. Fldigi has a very nice feature to playback WAV files and see
it in the waterfall from the "File" command so this might
--David
KI6ZHD
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