Hi
> On Feb 5, 2019, at 11:59 AM, Mark Goldberg <[email protected]> wrote: > > On Tue, Feb 5, 2019, 8:00 AM Bob kb8tq <[email protected] wrote: > >> Regardless of how you do it, isolation is an issue. Having a 10 MHz >> standard line with a very >> close in spur is not a real good thing. It can mess up a lot of stuff and >> it passes through the >> cleanup loops in most gear. Is 120 db far enough down? I’ve certainly seen >> problems from >> stuff at that level at a small offset …. Simply having a switch with this >> or that db isolation is >> just a starting point. Grounding and shielding are very much on the “to >> do” list as well. >> > > I was going to mention that. I modified my Perseus SDR to use an external > oscillator and just removing some SMT resistors to disconnect the original > oscillator output was insufficient. Still coupled in a spur from the > original oscillator and bad close in phase noise. I had to disable the > original oscillator by removing power. I didn't spend the time to try to do > that automatically. Maintaining phase continuity in the changeover would > also be hard. > > Do you have any examples of something small that does this well? Nothing that I have seen on the surplus market. Some of the things companies I’ve worked for over the years did a pretty good job ( at least to the specs the customer requested …). Bob > > Regards, > > Mark > > >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
