[RTTY] What's cleaner: FSK or AFSK?

[Joe Subich, W4TV]

With the K3 it doesn't matter - the K3 DSP passes both AFSK and FSK
through a narrow filter *after* the modulation stage.  The one limit
is that you cant go clicking around on the waterfall in AFSK because
you will quickly get outside the transmit bandpass filter.

With the FT-dx5000 AFSK is probably cleaner *if* you can be sure there
is no hum on your audio, that the audio does not cause clipping before
the modulator and the transmit *IF* stages don't have so much gain that
they generate clicks/sharpen the keying edges unnecessarily and cause
ALC overshoot on the leading edge of each pulse.

The problem is that most rigs come from the factory with excess IF gain
specifically so the manufacturers don't get complaints about low power
output.

73,

    ... Joe, W4TV


On 2/5/2014 8:31 PM, RLVZ at aol.com wrote:
> Hi Guys,
>
> I really appreciate _rtty at contesting.com_ (mailto:rtty at contesting.com)  as
> I've  still got a lot to learn about RTTY.
>
> Am I understanding recent comments  correctly that say "FSK stations
> typically have worse RTTY sidebands  and clicks than properly adjusted AFSK
> stations"?
>
> I wondering whether to use FSK  or AFSK on my K3 and FTdx5000.  Or perhaps
> AFSK on the K3 and FSK on  the FTdx5000?  (which method would create the
> cleanest  sidebands?)
>
> Hope to work you in the WPX RTTY Test this  weekend!
>
> 73,
> Dick- K9OM
>
>
>
> From: Kok Chen <chen at mac.com>
> To: RTTY Reflector  <rtty at contesting.com>
> Cc: Bill Turner  <dezrat1242 at wildblue.net>
> Subject: Re: [RTTY] Change in pileup  procedure?
> Message-ID:  <2F228A20-E260-46CE-A5AB-595256D3FA91 at mac.com>
> Content-Type:  text/plain; charset=us-ascii
>
>
> On Feb 5, 2014, at 12:38 PM, Bill Turner  wrote:
>
>> What am I missing?
>
> Let me explain.
>
> The keying  sidebands of a continuous phase FSK signal is down only about
> 50 dB, even when 1  KHz away from the signal.  A waveshaped AFSK signal or a
> K3 FSK signal will  not be as poor, and a phase coherent FSK signal will be
> much worse, but lets  assume that a lot of people in the pile are using
> continuous phase FSK (what  most DDS superhet rigs today use).
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