[RTTY] The Problem with AFSK ...

[Richard Ferch]

N1JM wrote:

> Do K3s key click using FSKD or 590s using FSK?

Yes. For the K3, the evidence has been published; the K3 is capable of 
producing cleaner RTTY (lower levels of key clicks) in AFSK than it is 
in FSK:

1. Read <http://www.frontiernet.net/~aflowers/k3rtty/k3rtty.html> (the 
article that triggered the current discussion).

2. Read <http://www.w7ay.net/site/Technical/K3/Content/digital.html>, 
where Chen made similar observations in early 2010.

3. Test for yourself. In March 2010, after reading Chen's article, I did 
an experiment with my K3, a dummy load, a separate receiver (a Kenwood 
TS-850), short wires for antennas, and MMTTY and spectrum display 
software. Using FSK D and AFSK A in turn on the K3, I transmitted idle 
(diddle) and RY signals from MMTTY at various power levels and on 
various frequencies into the dummy load and took screen shots of the 
signals received in the TS-850 using spectrum display software in a 
separate computer. In every case, the received AFSK signal had visibly 
lower shoulders than the FSK signal at the same power level. I would not 
want to claim that these measurements were anything more than a 
demonstration, but the results were clear enough to convince me that my 
K3's performance was not any different from what Chen and Andy have 
reported.

Now, it is true that I did take precautions similar to those that Chen 
has mentioned in this thread to avoid hum, noise and overdriving. I have 
no doubt that someone with an "all knobs to the right" mentality and 
with no understanding of how to produce a clean signal can generate 
absolute garbage using AFSK, especially with a transceiver that is less 
forgiving (idiot-proof??) in AFSK than the K3. I have seen it; we 
probably all have. But equally, I have no doubt that someone with a good 
understanding of these issues can produce cleaner RTTY using AFSK than 
the current generation of amateur transceivers produces in FSK. This 
will continue to be the case until the manufacturers start paying 
attention to key clicks in FSK RTTY.

I can't speak for the TS-590 from personal experience, but I have read 
and seen nothing that would make me suspect that it (or any other 
amateur transceiver) is significantly better (or worse) than the K3 in 
this respect.

73,
Rich VE3KI