AMBE is just the audio codec (source coding), it has nothing to do with
the actual channel coding (modulation), right?
And indeed, AMBE patents already expired some time ago... and there are
some open source implementations hanging around for some time, eg:
For eg., freedv uses codec2 or LPCNet for audio coding.
Rafael
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On 10/15/21 10:02 PM, Ken Hansen wrote:
The d-Star mode is open source, the chip that the two radio
manufacturers use is proprietary, but it is only out of convenience
that Icom and Kenwood use the AMBE vocoder. Just as Yaesu and Alinco
use the same chip to implement C4FM and DMR
Of course, one would need to learn Japanese to read the D-Star
specifications, but they are public, were developed by JARL, and are
available for anyone to implement without license fee.
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Personally, the AMBE chip (at about $20 in single qty) seems like a
bargain compared with other methods of implementing D-Star, DMR, C4FM,
etc., but opinions vary.
I can buy an AMBE board for about $150 and 'operate' D-Star on my
windows PC w/o a radio (but what fun is that?):
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That $150 board costs so much because it not only has the $20 AMBE
chip, but also a fair amount of other technology to support serial,
USB, WiFi AND Ethernet connectivity.
Ken, N2VIP
On Oct 15, 2021, at 10:19, Tom, wb6b <wb6b@...> wrote:
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Hi,
?
I¡¯ve ben doing a bit more reading on amateur radio digital voice
modes used on HF.
?
To focus on one possibility for a digital voice mode that may be
compatible with nonlinear RF finals, I discovered that D-Star is
being experimented with by some hams on HF.
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D-Star uses GMSK, Gaussian Minimum Shift Keying on VHF/UHF. Best I
can tell the modulation mode is not changed in the HF world.
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If so, this might be a way to add a voice mode to digital only modes
transceivers, with simple nonlinear RF output stages, like the QDX.?
?
D-Star uses a proprietary codec, so what I¡¯d *suggest is use the
frequency shift (GMSK) modulation method but swapping out the D-Star
codec for the FreeDV codec.?*
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Any major flys in the ointment here? Other than getting ham radio
operators interested in yet another voice mode?
?
There are, also, multiple frequency shift modes that might offer some
advantages. But GMSK seems the likely starting point for
experimentation or at least for this conversation.
?
I know there are folks that have gained much more knowledge of this
area than my beginnings at sorting through this area of knowledge.
Hopefully some of those folks will be able to add some practical
additional knowledge on the subject.
?
Tom, wb6b
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