[RTTY] Key clicks seemed less severe last weekend

[Kok Chen]

> On Sep 28, 2017, at 7:12 AM, Tim Shoppa <tshoppa at 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