Thanks for the reply, I will try these suggestions when I find enough
time for that and will write again if anything unclear or with results.
On 2013-05-12 16:09, Tobias Blomberg wrote:
> On 05/05/2013 10:09 PM, Alexander Dimitrov wrote:
>> Hi everyone,
>> I have SvxLink running as deamon on Debian squeeze 6.0.6 connected
>> not very good radio with even worse interface (both 20:1 divider
>> 4.7 uf capacitor, PTT is VOX on Tx, CTCSS on Rx/squelch), works fine
>> with some acceptable noise.
>> The problem is the DTMF digits are not all received properly, did
>> succeeded to transmit A-D and *, others are sometimes detected and
>> sometimes not.
> There are a couple of things you could try. It is very important that
> the audio level is not too high into the sound card. It's better that
> it's a bit low than too high. If it's too high you will get clipping
> which kills all signal processing, like DTMF detection. I have also
> sound cards distorting the audio if the capture level is brought
> 90%, no matter what the input signal was, so try to not push the
> level all the way up. If you think the audio level is too low you can
> always adjust it up digitally using the PREAMP configuration variable
> the receiver configuration section.
> The most likely problem in your case probably is that you have a
> "leaning frequency spectrum". That will cause the low tone and the
> tone to have too much level difference. There is a check in the DTMF
> decoder for this. Tones that differ too much in level are discarded.
> farther apart the low and high tones are, the harder it will be to
> detect the DTMF digit. I think that A is the digit that use the
> tone in the low tone group and the highest tone in the high tone
> The best thing to do is to try to get the frequency spectrum
> straightened up. Maybe your audio need to be deemphasized if you have
> connected to a 9k6 port on your rig? In that case, set DEEMPHASIS=1
> your receiver configuration section. If nothing else helps you can
> to experiment with the DTMF_MAX_FWD_TWIST and DTMF_MAX_REV_TWIST.
> is what the manual page for svxlink.conf say:
> DTMF use two tones to encode digits 0-9, A-F. These two tones
> should normally have the same amplitude. The difference in
> amplitude is called twist. Forward twist is when the higher fre‐
> quency tone is lower in amplitude than the lower frequency tone.
> According to the standards, 8dB forward twist should be allowed.
> Some transmitters do not correctly modulate the DTMF tones to
> get zero twist. The most common situation is that the forward
> twist is too large. Increasing this configuration variable above
> 8dB might allow DTMF from these transmitters to be detected.
> When doing this, the DTMF detector will be more sensitive to
> noise and might cause more false triggers.
> A nice tool to check your audio with is "audacity". This is a
> sound editor so if you have graphics on your SvxLink machine, install
> and fire up audacity. Press the rec button and you can follow what's
> recorded in real-time. Make sure the level does not hit the ceiling.
> Adjust the audio level until it's within limits. Now press DTMF digit
> on your transmitter for a couple of seconds. Stop the recording and
> part of the tone, and only the tone, by dragging the mouse over it.
> choose "Analyze/Plot Spectrum..." from the menu. Now you should see
> two tones and how much they differ in amplitude.
> If you don't have a graphical environment on your SvxLink computer,
> a utility like arecord to record some audio, then copy the recorded
> to a computer with a graphical environment and run audacity on the
> Example of running arecord:
> arecord -Dplughw:0 -r48000 -fS16_LE /tmp/recording.wav
> That will give you a mono recording. If you have more than one
> receiver, you'll need to add the -c2 switch to get both channels.
>> I've been thinking to simulate DTMF commands using some sort of
>> interface, which I can operate using SSH or web, last one is my
>> as long as I have operational interface to svxlink daemon, I can
>> automate it however I want using php, some bash scripting, js/ajax,
>> when coping with serious hangover.
>> Possible solutions I see so far:
>> 1. some quick and dirty modification in the code to read a file or
>> named pipe in which I can write DTMF digits "on the fly" using PHP
>> shell commands.
> You should fix the DTMF issue but if you really want to go the other
> I think it would be quite straight forward to implement that. In
> svxlink.cpp, just add a command line switch taking a path to a named
> pipe as an argument, open the pipe, create an Async::FdWatch to watch
> for activity on the pipe and connect it to a handler function. Maybe
> can connect it straight to stdinHandler but you may require some
> named pipe specific handling. I think that would do it.
> 73's de SM0SVX / Tobias
>> 2. set up a Voter with local udp stream, the streaming app (which I
>> yet to find) is supposed to play pre-recorded DTMF tones from files
>> (which also I am yet to find or generate).
>> Mute the commands on Tx (that I believe can be done with config) and
>> disable them on Rx (so the only available method for delivering
>> is "the interface") are optional, but desired features :)
>> I've looked through the mailing lists, read that there is a remote
>> control in the scratch list, but I don't need a full featured
>> control/monitoring suite, just to inject some DTMF digits, enough
>> now - voicemail, parrot, connecting to echolink nodes, doing some
>> with TCL modules and/or event handlers.
>> Found also this:
>> Start SvxLink something like this:
>> nc -lk 10000 | svxlink
>> Send it commands to connect to the Echolink node 12345:
>> echo -n "*2#12345#" | nc localhost 10000
>> not sure if that relates much to my issue, but seems close, I have
>> run svxlink with --daemon --runasuser --logfile --config --pidfile,
>> meaning - all options
>> Thank you in advance for the help, if you can help, otherwise, still
>> thank you for the time reading this :)
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