[RTTY] K3S with AFSK

[David G3YYD]

Jim

I use K3 with the "old" style interface. I have two K3. I have always used
low tone AFSK well actually 2Tone DOOK as it performs slightly better
(0.4dB) than AFSK and is narrower too. I listened on one K3 to the other K3
transmitting. The signal has no audio second harmonic that I can detect and
that means it going to be at least -90dB down on the wanted signal.

I tried to overdrive the K3 line in by turning the K3 gain to the max and
the same with the PC sound card. Again I could not hear any second harmonic
so input stage overload is not a problem either.

If you are using something like MMTTY to generate your AFSK then do switch
on the K3 AFSK TX filter using config AFSK TX to ensure the TX bandwidth is
definitely controlled. The MMTTY default setting results in a wide TX
signal.

73 David G3YYD


-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Jim N7US
Sent: 24 April 2017 21:44
To: 'RTTY Reflector'
Subject: [RTTY] K3S with AFSK

I'm replacing my K3 with a K3S and plan to use AFSK (using the internal
soundcard) after using only FSK for many years.

I prefer listening to low tones, 1225/1445.  I understand that high tones
are recommended for AFSK to prevent the possibility of transmitting the
second harmonic.

My questions are K3/K3S specific:

1) Are low tones OK?

2) Can/should the AFSK TX 400-Hz DSP transmit audio filter, which is
selected in the K3's configuration?  A friend just got his K3S and turning
on the filter apparently prevented the AFSK transmission, which leads me to
conclude the filter is designed for high tones.

I use DXLab with WinWarbler as my general logger, which can use only MMTTY
to transmit RTTY.  I understand that it's good to set MMTTY taps to 512 to
transmit a narrow signal, so I'll do that.  I'll also consider transmitting
AFSK with 2Tone when using N1MM+.

Any other suggestions?

Thanks very much. 

73, Jim N7US



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