Mike,
What I see in your video is that you have the RTTY signal properly tuned
at 14,091.883. "Properly tuned" means that you have the Mark energy and
the Space properly aligned in the dual passband filter and the data
conveyed by the mark and space energy is being decoded and displayed.
In a normal "ham radio" RTTY signal the RF energy for the Mark and Space
is 170 Hz apart, with the Mark frequency 170 Hz higher, in RF terms,
than the Space frequency. When demodulated by a receiver operating in
Lower Sideband (LSB) mode, this results in two audio tones, with the
audio tone representing the Space energy 170 Hz higher than the audio
tone representing the Mark energy. In the video, when your radio is
tuned to 14,091.883, the tone representing the Mark energy is passing
through the "Mark" side of the dual passband filter and the tone
representing the Space energy is passing through the "Space" side of the
dual passband filter, and the RTTY data is decoded properly. When you
tune down to 14,091.720 in the video, a 163 Hz difference, you have the
tone representing the Space energy passing through the "Mark" side of
the dual passband filter and the tone representing the Space energy is
outside of either portion of the dual passband filter. There is no
anomaly revealed in your video, that's just the way that RTTY, the
receiver, and the dual passband filter works when you tune away from a
properly tuned RTTY signal.
The reason the data on the Space tone sounds like an inverted version of
the data on the Mark tone is because that is exactly what it is. In an
RTTY signal, the same data is carried by the both the Mark and Space
energy and the state of one is the inverted state of the other.
73,
Bill - NA5DX
Message: 23
Date: Thu, 18 Feb 2016 09:56:06 -0700
From: Mike Murray<w0agm...@gmail.com>
To: "Wes (N7WS)"<w...@triconet.org>
Cc:elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 - AFSK anamoly? No replies, try again
Message-ID:
<CAP7zeEJBvJCVEY-=uu21OQTN=eavupuy_wf-lwz5_qoameh...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
After doing some more testing in last weekends RTTY contest, it appears
that I made an erroneous statement as to what I was hearing and where.
What I found is that as I tune down in frequency and find a signal that
will decode, if I then tune down another 170 Hz I'll hear the inverted
signal. Still using dual passband DSP filter at 400 Hz and 400 Hz, 8 pole
roofing filter as before. I have a brief video on uTube showing the effect
at:
*http://tinyurl.com/hxykq9c <http://tinyurl.com/hxykq9c>*
Anyone have additional thoughts as to what's causing this or where I should
look next?
Mike - W0AG
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
