[aprssig] DTMF on HF?

[david vanhorn]

Now from a real keyboard..

The conventional method for DTMF is 100mS per digit, 50 of tone and 50 of
silence.
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:
1.2.3.4-4.3.2.1 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
twist values.

This link has some good information on rates and twist.
http://www.genave.com/dtmf.htm



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
>>
>>
>>
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>>
>>
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