On Dec 29, 2010, at 12/29 10:12 AM, radioshoppe wrote: > As mentioned in my email about the best I can do with Method 2 is > about +/20 hz.
Do you have an RTTY program that has a crossed-ellipse display (affectionately called "crossed bananas" by RTTY nuts)? If so, that might get you closer than 20 Hz by using your sight instead of your hearing. A steady Mark tone should appear as a single oval that is perfectly vertical or perfectly horizontal. You tune your rig by the amount of the mark tone that you have set -- if you can set the mark tone to some "nice" tone, like 2000 Hz instead of 2125 Hz, you won't have to do much mental gymnastics to figure out the proper VFO offset. Not all software have a narrow cross ellipse display, so you may need to find one that is satisfactory. Basically, with the standard RTTY shift, the cross-ellipse will go through 90 degrees of rotation with 170 Hz worth of offset. If you can find software which you can change the FSK shift, you can get even more accurate readouts. For example, setting the shift (i.e., the difference between the Mark and Space tone) to 50 Hz will move the peak of the oval by 90 degrees with just a 50 Hz VFO offset. I just tried WWV in cocoaModem's "wideband RTTY" display (whose oval is narrower than for other RTTY modes in cocoaModem). By using an FSK Shift of 10 Hz, I can easily eyeball a 1 Hz change. If your RTTY software does not allow such a narrow shift, it might have MSK (Minimal Shift Keyed) mode, where the shift is 22.5 Hz. (Note: MSK, not MFSK; they are different animals.) If you are using WWV, be sure to use a narrow filter so the modulations don't come through, or wait for the sidetones and subcarriers to stop. Else you will get an oval that shakes around :-). Alternately, you can look for iPhone apps for tuning musical instruments. Set your VFO offset for middle C or something :-). 73 Chen, W7AY ______________________________________________________________ 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
