> On Sep 28, 2017, at 7:12 AM, Tim Shoppa <tshoppa@gmail.com> wrote:
>
> I don't track the waveshaping improvements ( see K0SM's article
> http://www.frontiernet.net/~aflowers/k3rtty/k3rtty.html ) through every
> possible contesting rig hardware/firmware update, but I suspect that K0SM's
> lessons have been taken up by several manufacturers in the past 5 years.
The only manufacturer that changed behavior was Elecraft.
Instead, the reduced keyclicks have come from change in behavior of operators,
as more people turn to use AFSK.
This is especially true as people migrate to direct sampling SDRs like Flex,
Icom 7300 and HPSDR (ANAN rigs), where the transmit signal is generated by
digital to analog converters at RF frequencies, with no nonlinear analog
components like mixers in between. The AFSK that the modem generates
mathematically is precisely the AFSK signal that the RF amplifier sees.
Just using AFSK is by itself not a guaranteed cure. More importantly, the AFSK
signals are cleaner as more modem developers use severe waveshaping of
individual Mark and Space tones (e.g., 2Tone and fldigi) instead of just a
bandpass filter around both tones. Thank them instead of thanking the rig
manufacturers :-).
Another thing that AFSK transmitters improve is the reduced jitter; there is
simply no jitter with AFSK. That in turn allows the receiving modems to throw
fewer errors, even when copying very strong signals. I.e., transmit with AFSK,
and you will require fewer repeats, compared to using FSK transmitters that
bit-bang to generate the bit timings. This is not just a pie in the sky thing;
I am sure David G3YYD has measured it when designing 2Tone.
73
Chen, W7AY
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