[aprssig] DTMF on HF?
kc6ete at gmail.com
Fri Jan 10 18:38:20 CST 2014
Now from a real keyboard..
The conventional method for DTMF is 100mS per digit, 50 of tone and 50 of
1-2-3-4-4-3-2-1 with the dashes being silence (not very critical about
noise during that interval)
The fast way is to reduce or eliminate the space between different digits:
184.108.40.206-220.127.116.11 with the dash being 50ms and the dots being 0-10mS
How far you can shrink that timing depends on the decoder involved, I have
seen 0 work perfectly.
In my experience, the biggest hindrance to proper DTMF decoding is bad
This link has some good information on rates and twist.
On Fri, Jan 10, 2014 at 4:16 PM, david vanhorn <kc6ete at gmail.com> wrote:
> Ssb would be a problem. S/n ratio can be pretty poor, but the one thing
> most decoders hate is twist. Telco lines attenuate the higher pitches more
> than the low. Check the datasheet of the decoder you plan to use.
> Fwiw, you can almost eliminate the interdigit silence if the digits are
> different. More later
> On Jan 10, 2014 3:43 PM, "Robert Bruninga" <bruninga at usna.edu> wrote:
>> Has anyone had any experience with any success at DTMF working on HF for
>> some rudimentary commands?
>> I know tuning is critical as well as inter-tone noise must be way down.
>> Just thought maybe someone has experimented with it.
>> Bob, WB4aPR
>> aprssig mailing list
>> aprssig at tapr.org
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