On 2/26/2018 3:11 PM, David G3YYD via RTTY wrote:
I looked at programming a PC connected UART, but all the
specifications I looked at for current stock are incapable of doing
45.45 they do 45 if they can go that slow.
The way to get a PC connected UART to do 45.45 baud is to *hack* the
standard serial driver to rewrite 45 baud to 45.45 baud (change the
baud rate divisor for 45 baud to 45.45 baud - decrease the value of
the baud rate divisor by 1%). That was a whole lot easier in the days
of MSDOS and Windows 3.1/95/etc. but should still be doable with the
proper software tools.
I believe one of the older USB (1.0) to serial bridge chips even
provided a way for the product maker to do so by customizing the
drivers (it was called "aliasing" - any standard baud rate could be
rewritten to any custom baud rate within the 230 kbps maximum data
rate limit).
73,
... Joe, W4TV
On 2/26/2018 3:11 PM, David G3YYD via RTTY wrote:
Joe and Ed
Yep TinyFSK does an excellent job, which is why I made a bespoke driver
within 2Tone for it. In testing TinyFSk I found no detectable timing jitter.
I looked at programming a PC connected UART, but all the specifications I
looked at for current stock are incapable of doing 45.45 they do 45 if they
can go that slow.
Still does not avoid the wide radio FSK problem. Nor as pointed out wideband
TX noise/oscillator phase noise. The later of course is with us whatever the
mode used.
The K3 is, as far as I know, the only radio that filters its FSK signal so
it has a reasonable FSK bandwidth. There may be another but I do not know of
one.
The K3 driven by a sound card is the set up I use for SO2R contesting. I
tried to overdrive a K3 by setting all the gains in the PC and the K3 to the
maximum. I then looked at the K3 TX spectrum using the other K3. I could not
see detect any spurious due to overdrive at all.
The K3 line in was connected direct to the sound card line out with no
transformer or attenuation. Conclusion I came to is the K3 is very well
engineered in this area (as it is in many other areas of performance) and to
have no worries about overdriving it with audio.
Note the very cheap $5 USB sound cards are not very good so better to use
$25 ones. More expensive ones are just as good but you pay more $ than
needed.
73 David G3YYD
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