Very nice work, Andy...
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: aflowers@frontiernet.net
Sent: Thursday, March 21, 2013 8:16 PM
To: RTTY Mailing List
Subject: [RTTY] K3 reduced-bandwidth RTTY analysis
Hello again,
I have finally gotten around to finishing up a short analysis of the
reduced-bandwidth FSK keying in the K3. As many of you are aware, Elecraft
made some beta firmware available several weeks ago that attempts to reduce
the clicks that result for unshaped keying. They analysis involves a before
and after pictures comparing the FSK spectra from the general release
firmware (representative of most radios, to the best of my limited
knowledge) and the bandwidth-reduced firmware. I've also included some
analysis using a 300 Hz "roofing filter" to measure the noise floor at
different dial offsets from the transmitter to give and idea of what it
"feels" like when it is QRM. There are a few people who operated WPX and
and other contests with this firmware, and I am sure they could tell of
their experiences on the transmitter side.
http://www.frontiernet.net/~aflowers/k3beta/
While on the subject of clicks, spurs, and other nasty things, I also would
encourage people to have a look at N2QT's question on p. 55 in the April QST
and WB1GCM's (at ARRL Lab) response, which also address this and some other
issues around RTTY keying. He distinguishes "clicks" that result from the
waveform from the other bad things that can happen with broken audio signal
chains. This is an important distinction to keep in mind.
Enjoy!
Andy K0SM/2
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