[digitalradio] Re: RTTY and mode selection on radios
If the radio has RTTY as a mode, as does the TS-940 for example, it means (1) there is an input on the back where you put in a baseband signal and FSK comes out the antenna, and (2) for receiving it will use a narrow filter and center the filter up around 2.2 KHz. (By baseband I mean the actualy RTTY signal at 45.45 baud, as would come out of a Teletype keyboard.) In the case of the TS-940 and other radios there is a misfeature that in SSB mode you can't get the narrow filter switched in; you have to use RTTY or CW mode to get the narrow filter. The main reason you want the narrow filter is to suppress strong signals that are in the IF passband of the radio but not in the middle of the signal you are trying to receive. Such signals will affect the gain of the receiver through AGC action, so that the level of the desired signal goes up and down as those off-channel signals come and go. So you want the narrow filter to have the AGC focus on the signal you are trying to receive. The reason the receiver puts the filter up at 2.2 KHz in the FSK mode is that in olden days FSK signals were translated to audio, originally at 2125 and 2975 Hz, later changed to 2125 and 2295 when 170 Hz shift came into use. So if you were using a typical RTTY terminal unit for receiving its input frequency range would be up there. Jim W6JVE
[digitalradio] Re: RTTY and mode selection on radios
--- In digitalradio@yahoogroups.com, John Becker, WØJAB w0...@... wrote: RTTY should be used in the LSB mode regardless of the band. Well thats when you aren't using the FSK mode for RTTY; the FSK mode does put it into LSB. I don't use software for RTTY so I cant tell you a thing about that. Users of software for RTTY have come around to using USB regardless of band, just for the sake of uniformity. In that case they use a reverse shift switch in the software to make the signals come out right side up.
Re: [digitalradio] Re: RTTY and mode selection on radios
I use USB dfor FSK, simply because I want the low side of the signals to show up on the left side of the waterfall, and the high frequencies to show up to the right. Because that puts me opposite than the normal signals, I run both send and receive with the reverse button clicked.' Danny Douglas N7DC ex WN5QMX ET2US WA5UKR ET3USA SV0WPP VS6DD N7DC/YV5 G5CTB All 2 years or more (except Novice). Short stints at: DA/PA/SU/HZ/7X/DU CR9/7Y/KH7/5A/GW/GM/F Pls QSL direct, buro, or LOTW preferred, I Do not use, but as a courtesy do upload to eQSL for those who do. Moderator DXandTALK http://groups.yahoo.com/group/DXandTalk Digital_modes http://groups.yahoo.com/group/digital_modes/?yguid=341090159 - Original Message - From: jhaynesatalumni To: digitalradio@yahoogroups.com Sent: Friday, February 19, 2010 5:44 PM Subject: [digitalradio] Re: RTTY and mode selection on radios --- In digitalradio@yahoogroups.com, John Becker, WØJAB w0...@... wrote: RTTY should be used in the LSB mode regardless of the band. Well thats when you aren't using the FSK mode for RTTY; the FSK mode does put it into LSB. I don't use software for RTTY so I cant tell you a thing about that. Users of software for RTTY have come around to using USB regardless of band, just for the sake of uniformity. In that case they use a reverse shift switch in the software to make the signals come out right side up.
Re: [digitalradio] Re: RTTY and mode selection on radios
Of course. Not being a sound card guy when it comes to RTTY. John, W0JAB At 04:56 PM 2/19/2010, you wrote: I use USB dfor FSK, simply because I want the low side of the signals to show up on the left side of the waterfall, and the high frequencies to show up to the right. Because that puts me opposite than the normal signals, I run both send and receive with the reverse button clicked.' Danny Douglas
