Rex Moncur wrote: > Hi Said and All > > I have been following this thread with a lot of interest because my > application is also in portable Microwave operations with narrowband modes > such as WSJT. The main issue here is not so much long term frequency > stability as one only has to find a signal in an SSB passband, but the > short-term stability should preferably be better than a few Hz over a 46 > second transmission. A second issue as others have mentioned is that one > needs to have a stable signal at a new location within a relatively short > period for many rover operations (say 15 mins). > > (Note: I earlier asked a question about short term stability with my Trimble > Min-T and this has been solved by increasing the Time constant from the > default value of 10 seconds to 200 seconds. The short-term stability is now > better than one part in 10^10 which is the limit to which I can measure) > > Now to my Question: I note the importance of the self survey for absolute > time but I wonder if a self survey is important for accurate frequency where > the absolute time is not an issue? > > There are number of things that it seems one could do to achieve frequency > stability as fast as possible at a new location. > > 1. Run the Oven off batteries full time - this can be typically only 3 to 5 > watts - for the Mini-T or the Fury. > 2. Record the EFC voltage at the home location and insert this in software > as starting point at the portable location. > 3. Insert the position information in software of the portable location as a > staring point. > 4. As Said suggests run a short self survey of only a few minutes. > > Now I am not sure which of any of the above points are necessary or > important but I would be grateful for the thoughts of others. > > Regards Rex VK7MO > Rex
If you make provision for multiple power sources with preassigned priority its not necessary to run of a battery all the time, however the battery needs to be present as a backup when the other power supplies are disconnected. Achieving this without disturbing the power supply voltages when switching between various power sources requires careful design, a simple diode OR circuit is in general inadequate particularly if more than 2 sources (mains, external dc, internal battery) are available, however the required circuity need not be overly complex. Bruce Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
