I am trying to figure out whether I should throw away my old WE 247B KTU touch
tone decoder. Anybody want it?
Museum maybe? Put some pull ups on it and it should not be too hard to do a 12
line to hex converter,
in software. You can't beat the old pot cores and precision caps for
acquisition time, it ain't exactly false proof.
When I was working late at night, alone up on Santiago I had a habit of turning
down the HT-220
because it was barfing intermod continuously. So the guys would do cat call
whistles into the rptr
to get my attention with the chattering relays. Please, this thing has 20
years of service and sacred rodent
excrement included. I can't just throw it away?
td
wb6mie
2a. Re: DTMF Decoder
Posted by: "Ron Wright" [EMAIL PROTECTED] n9eerptr
Date: Wed Mar 26, 2008 4:19 am ((PDT))
I have never played with a computer sound card other than the typical plug it
in and let the various program drivers interface to it.
I bet the sound card is a simple ADC and software looks at the wave form using
a look up table that compares what is received and reacts.
DTMF is much more complex, simple in theory, but can be complex. With varying
tone levels, distortion, harmonics, etc the wave form changes drastically.
Dedicated circuits and ICs do a much better job.
73, ron, n9ee/r
