Andy, Regarding matching the RTTY tones... matching a tone is difficult for some people and easy for others. For example, some people sing off key! Were you good at matching the note of the pitch pipe in music class? :-)
You said some RTTY signals did not sound the same as yours. I heard this as well, and one was so blatant I had to look at my scope! The reason for this dissimilar sound is because some fellows overdrive their transmitter audio input when using AFSK. This generates distortion, harmonics and secondary signals. I hear this during every RTTY contest and last weekend was no exception. A bad soundcard or driver could be a potential problem as well, but not as likely as excessive mic gain. If a RTTY signal is generated by AFSK and the audio is not pure, it will sound different from good 2125 and 2295 tones. It's the same principle that a middle C note on a violin sounds different than the same note on a clarinet. Both instruments produce the same fundamental frequency, but each has its unique signature of harmonics and overtones that allow you to easily distinguish between them. So now you know why a lot of RTTY operators say this mode is "music to their ears"! But why are they called "green keys"? A piano is black and white. 73 de Bob - KØRC in MN ----- Original Message ----- From: Andrew O'Brien To: digitalradio@yahoogroups.com Sent: Monday, February 11, 2008 7:26 PM Subject: [digitalradio] Re: Operating FSK RTTY in a contest ? -Bob, thanks for your helpful advice. I am interested in your comments about matching the RTTY tones, his and mine. A few times over the weekend I did note that my tones did not sound as musical as the tones I was decoding. Looks like I need more practice with RTTY FSK. Andy. -- In digitalradio@yahoogroups.com, "Robert Chudek - K0RC" <[EMAIL PROTECTED]> wrote: > > Andy, > > When using FSK and the MMTTY/N1MM software, the NET button has no effect. That button is used only when your setup is configured for AFSK mode. > > Regarding the AFC button, you may or may not want to have that turned on. It depends on how you are operating. When you are searching for stations to work, you would have the AFC turned OFF. You can think of this as locking the MMTTY decoder tones to 2125 and 2295 Hz. You have the right idea in your message. > > If you are sitting on a frequency, calling CQ, and having stations come back to you, then you may want the AFC turned ON. What this does is to release the MMTTY decoder so it can Automatically Frequency Correct (AFC) its internal filters to capture a station that may be calling you that is off frequency. > > You can see how this works by starting with AFC turned off. Tune to a DX station that is calling CQ. Get your waterfall, bandscope, and XY display lined up. Note the "Mark" window will say 2125. Now turn the AFC on. Watch this window as stations come on frequency and call the DX. Some stations may be exactly on frequency, while others will be off. For the stations that are off frequency, you will see MMTTY automatically adjust that "Mark" window number, up or down, depending whether the caller is low or high from zero beat with the DX. This number "jumps around" a bit, but you can get a close approximation how far off of zero beat a caller is by subtracting 2125 from the number that appears in this window. If it reads 2025 you know they are 100 Hz from zero beat. > > To ensure you are "on frequency" for a caller, the first thing is to make sure you are using the monitor to listen to your own TX signal. If you're musically inclined, you can simply match the pitch of the station you are calling to the pitch of your monitor. Beyond that, the MMTTY audio bandscope is probably the most accurate tool. You can also enable the FIR demodulator. Click the "Type" button and look above the Mark window. There are 3 demodulators that you cycle through by clicking the button. The FIR demodulator gives you a very sharp + symbol on the XY scope. And of course double check your TS-2000 menu settings to make sure your FSK is set for 170 Hz and the standard tone pairs of 2125 and 2295 Hz. I don't have a TS-2000 manual, but Kenwood is pretty good about documenting the RTTY stuff so this information should be in there somewhere. > > In two weeks there will be the NCJ RTTY NA QSO Party, a 10-hour event that is a lot of fun. Check it out here: http://www.ncjweb.com/naqprules.php > > 73 de Bob - KØRC in MN > > > > ----- Original Message ----- > From: Andrew O'Brien > To: DIGITALRADIO > Sent: Sunday, February 10, 2008 6:39 PM > Subject: [digitalradio] Operating FSK RTTY in a contest ? > > > By the way, my TS2000 is one year old today, one year at my shack. > > With the TS-2000 being my first rig that could do FSK RTTY, I have not > got around to much RTTY contesting in the past year. I dabbled a > little today in the CQ RTTY contest, my old RTTY contesting used to be > exclusively AFSK sound card RTTY. I have mainly used Winwarbler for > FSK with the TS-2000, but in the RTTY contest this weekend I used > N1MM Logger and the MMTTY Engine. I had a few odd things happen, 4-5 > times I could have sworn that the station I was working moved up the > dial a few Hz. I was in hunt and pounce mode. I tuned the station, > decoded him, transmitted, and they answered. A few times in the QSOs > I noticed them 100-200 Hz from where they started . One station that > this happened to came back to me and said I was "off frequency". > When operating FSK RTTY, is it standard to work with NET and AFC OFF? > I had both off during the contest, since I assume that with FSK I need > to transmit exactly where I tuned the station (I used the MMTTY > spectrum display to tune the station precisely). I wonder if the > stations that appeared to drift were stations with their AFC "on", and > something drew them up the band a little ? Maybe I am doing something > wrong with MMTTY in N1MM? I had MMTTY set for the standard "HAM" > profile. How does one ensure you are "on frequency" in FSK RTTY ? > > -- > Andy K3UK > www.obriensweb.com > (QSL via N2RJ) >
