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
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