> It all depends on what your goal is. A couple of Hertz at 10 MHz will > keep you well within any of the HF ham bands. > > The following addresses beyond the 'Gotta stay in the band' issue. > > The problem with the Zero-beat-WWB-at-10-MHz technique is that WWB is > changing frequency. Not at the transmitter, but on the way to your > receiver. > > The atomic standard synched 10 MHz signal is going thru a process that > adds Doppler shift to your received signal. > > The ionosphere (at HF) is NOT a mirror, but instead is a ever changing > mix of ions that "appears' to change the height at where the reflection > seems to occur. This phenomena, the change of the apparent path length, > and thus the received frequency, is a form of Doppler shift. > > The HF radio time standards CHU, WWV, etc. all suffer from this problem. > There is a Yahoo group, <fmt-n...@yahoogroups.com>, which has lots of > information on attempts to circumvent this issue.
This is why I suggested a method of using a digital averaging scope to look at the WWV pips and watching them "walk" several days ago. Phase tracking is unreliable at best, IMO, at HF. -John ============= > WWVB @ 60 KHz offers an improvement in the Doppler problem in that the > propagation at 60 KHz is primarily by groundwave. > > Why would one want to have better accuracy and stability? > > FMTs, aka Frequency Measuring Tests, are pre-announced listening > activities where participants attempt to accurately measure the > frequency of signals broadcast in the amateur bands, typically 160 thru > 40 meters. > > See <http://www.k5cm.com/> for some examples of what hams and electronic > experimenters have been doing in this area. Connie and others have been > running tests on a more or less monthly basis. > > Here is one example of a 'good' setup for this activity: > > http://www.ve2azx.net/technical/FMT/fmt_info.htm > > A different use. I personally 'chase' NDBs, Non-Directional Beacons, > attempting to log these low power aircraft navigation aids located > mostly below the AM broadcast band. Identification of the modulated cw > sidebands normally is within a Hertz or so. > > A review of this lists archives will show many more interesting and > unique times and frequency pursuits. > > It all depends upon what you want to do. > > Joe, K9HDE > > PS The phenomena of two signals beating against each other is called > constructive and destructive interference. When in phase, you get twice > the signal strength or +3dB, when out of phase, complete elimination of > the signals. > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.