[arm-allstar] Kenwood TH-D74A DTMF issue

[Doug Crompton]

Jan,

 Most transceivers have the capability to run narrow or wide FM. Amateurs
except in very limited cases use WIDE FM. Changing your transceiver to
narrow FM is NOT the way to fix DTMF issues. Running a transceiver in
narrow will essential halve you deviation. About the same thing could be
accomplished by turning down your wide FM deviation. If you set it to
narrow you will not be able to achieve proper voice deviation on transmit
and on receive it could be distorted.

What this tells me is that it is a level issue and you need to see if there
is a level control on your transceiver for DTMF. Just because your voice
level is set correctly does not mean you DTMF levels will be correct.

There also might be frequency response issue. DTMF consists of two tones
for each character. One from a low frequency group and one from a high
frequency group.  Any difference in the tone levels will result in the tone
not being detected. This called twist.

https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling

DTMF detectors whether hardware or software are particular about tone
specifications because if they were not there would be undesirable voice
falsing conditions.


On Mon, Sep 3, 2018 at 3:57 PM "Jan Timmers via ARM-allstar" <
arm-allstar at hamvoip.org> wrote:

> Hi there - using a new Kenwood handheld with my AllStar node (45868) and
> noticed that I would have issues using DTMF *3(node) to connect my node to
> others.  Using CLI from the admin menu while pushing the keys on the
> handheld, I notice that all the characters echo properly, except 3.  The
> other keys I can hold down and they echo only once.  When I hold down 3 it
> echoes numerous times.  The only time a connection between nodes would
> complete properly was if I held the 3 down just a very short period of time
> (ie: less than 1/2 a second...) so that the proper sequence was sent.
>
> So I've been doing some experimenting with this handheld, and also did some
> google search using keywords "TH-D74 AllStar node DTMF" and saw others had
> similar issues.  I saw one possible solution might have something to do
> between FM and NFM.  I see that my TH-D74 has that setting, and I've been
> using FM with my AllStar node.  I change the setting on the handheld to NFM
> with the frequency (434.850 and PL 162.2) I use to connect to my node, and
> looked on in wonder and amazement to see that now I have a properly
> functioning DTMF 3 (confirmed with CLI).
>
> I've seen a youtube video about the difference with FM and NFM as it
> relates to AllStar communications (apparently NFM is not very acceptable as
> audio quality suffers), but if I want to use DTMF with the equipment I
> have, it's what I will need to do.
>
> Just an observation about my own experiences.  And to assist others that
> may have a similar situation to mine and were also wondering about a
> resolution to their problem.
>
> Regards;
> John Timmers VE7JBT
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