I suspect that at least part of the discrepancy is due to the following fact: The frequency on the radio's display and the frequency actually being transmitted on in RTTY are not always the same, depending on the radio and the mode it is being used in.
K3: In FSK D and AFSK A modes, the K3's dial displays the actual Mark frequency of an RTTY signal (provided you tune the signal to match the PITCH setting in these modes, i.e. so the Mark audio tone is 2125 Hz when the PITCH is set to 2125). However, in DATA A, the K3 displays the suppressed carrier (or BFO) frequency. Since DATA A is upper sideband, in DATA A the actual transmitted Mark frequency would be 2.295 kHz above the displayed frequency, assuming MMTTY is using the default 2125/2295 tone pair (reversed because of the sideband choice). The same is true in USB mode. On the other hand, in DATA A-REV and LSB, the actual transmitted Mark frequency would be 2.125 kHz below the displayed frequency. K2: This I am not sure of, but my first guess would be that the K2's display in RTTY mode is the suppressed carrier frequency (like the K3 in LSB mode). FT-950: The frequency displayed will probably depend on the mode being used. If the FT-950 was in FSK (RTTY-LSB) mode, then I believe it would display the actual transmitted mark frequency. On the other hand, if it was in AFSK (PKT-LSB or PKT-USB) mode, it would likely display the suppressed carrier frequency, unless the radio's packet frequency display offset has been changed from the default (0). Most RTTY software these days has the capability to perform the arithmetic (suppressed carrier plus or minus audio mark tone) so that it automatically logs the correct transmitted Mark frequency. In MMTTY, if you are using the "Radio command" feature, you can set the frequency offset to OFF (e.g. for FSK), LSB, or USB to have the program perform the required frequency adjustment in the log. The offset you observed was somewhat different from the expected 2.125 or 2.295 kHz. A couple of possibilities spring to mind. Perhaps the frequency calibration is off on one of the radios, or perhaps one of you was not using the default audio tones (for example, if you fine-tuned by clicking in the MMTTY waterfall). The best way I can think of to sort this out is to set MMTTY to its HAM defaults and turn AFC off, then tune the radio to an RTTY signal on an accurately known frequency (e.g. W1AW bulletins) and observe the radio's dial reading versus the published frequency. 73, Rich VE3KI W0EM wrote: > in the process we found > that on both bands his radio (FT-950) is receiving and transmitting 2.69 Khz > below my frequency. My K2 and K3 transmit and receive to each other on the > same frequency. We tried changing various settings in his and my radio's > and in N1MM and MMTTY at his location and mine with no change. > > It sure would be wonderful if someone could shed some light on this latest > head scratcher. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
