Vern, I have not used a sound card for DTMF decoding, but the decoder on the Echolink card (I am assuming for the repeaters you are using one) I find DTMF decoder problems are almost always level related.
Most decoders work over a reasonably wide range including twist (the difference between the high and low group tone levels). The ones in the phone company are usually tighter than most...they are very good. However, in radio systems one often does have the advantage of good flat audio. When you say some digits work and some do not this is usually a level problem and usually requires a separate adjustment from other audios. If the decoder is receiving say over 10% distortion the low group tones will get into the high group causing problems. It may be difficult to check the levels on a sound card...at least once it gets inside and then to the card audio. 73, ron, n9ee/r >From: [EMAIL PROTECTED] >Date: 2008/03/24 Mon PM 07:07:33 CDT >To: [email protected] >Subject: Re: [Repeater-Builder] DTMF Decoder > >I have messed around with the settings in Echolink a good >bit. > >The thing that is interesting is that 2 other repeaters >that were working fine stopped working within the past few >weeks. We believe it might have been some kind of windows >update or something. Mine used to work OK but has not for >some time. > >All of them will decode some tones. I had thought about >going to an external sound card but thought that a decoder >would be better. I just don't want to take the chance of >getting another sound card and having it not work. > >Vern > >On Mon, 24 Mar 2008 16:10:54 -0700 (PDT) > Jim Brown <[EMAIL PROTECTED]> wrote: >> Vern, it sounds like you may have some other problems >>that might cause a hardware DTMF decoder to work no >>better than the one in the sound card. It has been my >>experience that the internal sound card decoder works >>better than the external variety because of the various >>tweaks you can use on the internal decoder. >> >> Look for excessive distortion in your audio signal, or >>improperly deemphasized audio for your problem. Perhaps >>you have some problem with your sound card, but that is >>not too likely. I did have a brand new Dell computer >>with the sound card so out of calibration that the tones >>in the bubble up of a repeater sounded distinctly lower >>in pitch when passed through to EchoLink. When we went >>to an external SignalLink USB sound card the problem went >>away. >> >> You can tweak the sound card decoder by changing the >>'twist' or unbalance in level between the high tones and >>the low tones in a DTMF digit. One clue to this twist >>problem is that some TT digits will decode and some will >>not. Almost always this type problem can be compensated >>for by changing the twist settings in the sound card >>decoder. Look in the Sysop setup/DTMF/Advanced menu and >>try adjusting the twist up and down a few dB at a time. >> >> Does your EchoLink audio sound high pitched or 'tinney'? >> If so, you may be taking audio from a receiver that has >>not had the deemphasis compensation applied. Be sure to >>correct any audio issues before trying to get the >>internal DTMF decoder to work. Audio may be deemphasized >>by passing it through a series 15K resistor and placing a >>.22 cap across the output side of the resistor to ground. >> This audio may then be applied to the Mic input of the >>sound card. >> >> 73 - Jim W5ZIT >> >> [EMAIL PROTECTED] wrote: >> Any one know if there is a >>good hardware DTMF decoder out >> there or plans for one that will work with Echolink? >> >> There are several of us who had working Echolink >>internal >> DTMF that no longer can get them to tune up right. We >>are >> tired of messing with it so we want to go external. >> >> All I have found on the internet are full echolink >> controllers with DTMF built in. I want just the DTMF >> decoder part. >> >> Thanks, >> Vern >> KI4ONW >> >> >> __ >> >> >> >> >> --------------------------------- >> Be a better friend, newshound, and know-it-all with >>Yahoo! Mobile. Try it now. > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
