John Ackermann N8UR wrote: > Dan Rae wrote: > >> Richard W. Solomon wrote: >> >>> The GPSDO I want to use has an output rich in harmonics. In some >>> cases that is good, but Murphy rules and in the application I have >>> today, it is not good. >>> >>> I need a 10 MHz Band-Pass Filter, Bandwidth is not critical, something >>> small with SMA connectors would be ideal, but I can live with BNC. >>> >>> Anyone have such a beast or know where I can get one ? I checked >>> Mini-Circuits >>> and choked on the price !! >>> >>> >>> >> Dick, it is really easy to build one. The wonderful (free!) filter >> design program ELSIE will give you all the help you need. I would have >> thought an hour or so with a couple of toroids would do the trick. Even >> just a Low Pass filter would usually do to turn a square wave into a sine... >> > > It's actually much better to use an LPF than a bandpass filter if you > don't have subharmonic energy to deal with. An LPF with a cutoff midway > between the fundamental and the 2nd harmonic will show much less tempco > (in the form of phase shift over temperature) than a bandpass filter. > > John > > John
Another approach is to use relatively high Q traps/bandstop filters to eliminate/minimise the unwanted harmonics together with a low pass filter. The high Q traps contribute little phase shift and phase shift tempco at the fundamental. 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.
