On 12/28/2017 10:58 PM, Keith VE7GDH ve7gdh@... [ui-view] wrote:
Stephen WA8LMF wrote¡
Yaesu's "C4FM" is a proprietary format entangled
in licensing issues.
Are you sure about the word proprietary? I thought it was just the AMBE chip
that was licensed. When does the AMBE patent run out?
It's not the AMBE vocoder that is the issue. Practically all the digital voice
formats use it.
It's the way the digital data stream coming out of the vocoder is diced,
sliced, surrounded by error-correcting codes, packetized into blocks of varying
lengths, headers added, varying bit rates, etc before any of this hits the
actual radio modulator that make the various formats transmitted over
4-frequency FSK incompatible with each other.
PS - if you don¡¯t like the term C4FM, you could just call it System Fusion.
System Fusion is also a horrible term - it refers to the automatic recognition
and switching between analog and digital modes. It doesn't say anything about
the nature of the digital mode used.
There¡¯s a lot more to the FTM-400 than not being able to send data to the TNC.
However, the original poster was primarily interested in the use of UIview with
the radio - i.e. TNC connectivity issues.
The FTM-400 is a dream to use. C4FM (OK, System Fusion!) sounds a lot better
than D-STAR.
Agreed.
All the other digital voice modes attempt to cram the data stream into a 12.5
KHz occupied bandwidth (i.e. equivalent of 2.5 KHz analog deviation),
constraining the possible bitrate for the sampled audio. ?? The result is
either a higher error rate or muffled crappy audio or both. ? Yaesu's digital
format is the only one that uses the full 20/25 KHz radio bandwidth (i.e.
occupied bandwidth equivalent to a classic 5 KHz-deviated analog FM signal).?
This supports a higher bit rate and higher-quality audio stream that sounds
almost analog.
In the US, at least,? it has been MANDATORY in ALL the NON-ham radio services
(commercial land mobile, public-safety, etc) since 2014 (I think) to use an
occupied RF bandwidth no wider than the equivalent of a 2.5KHz-deviated analog
FM signal.? ( I.e. 12.5 KHz channel spacing.) ? You can opt for 2.5KHz
"sliver-band" analog FM, but the vast majority of users have switched to
low-bit-rate narrow-band digital formats. ? (2.5KHz-deviated analog FM is
awful. There's half as much audio recovery as the classic 5KHz FM, so the
slightest loss of full quieting is deadly, and virtually no impulse noise
suppression. At such a low deviation index, it's practically like AM!) ?? This
is all in aid of doubling the number of land-mobile radio channels at the
expense of audio quality.
We in the amateur bands ARE NOT subject to this narrow-banding mandate.
Narrow-band digital modes are a solution looking for a problem in the ham
bands.? The wider-banded Yaesu digital fomat with it's potential for
simultaneous data and decent voice due to it's wider bandwidth makes far more
sense to me.
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