Well, if one just looks at the spec of the 10811A for relative performance, it is -140 dBc/Hz at 100 Hz offset at 10 MHz. Realistically, probably a little better. From that it would be real easy to generate the frequencies Frank is looking for, obviously 20 would be easy but would be only -134 dBc/Hz at 100 Hz away. 22 would be easy by diving the 10 and mixing it with the 20, assuming the divide by 5 has a very small contribution, the PN of the resultant at 2 MHz is also theoretically 20logN better, so, mixing will also give close to -134 dBc at 100 Hz away. 42 can easily be generated by doubling the 20, to get -128 dBc at 100 Hz and then mixing with the same 2 MHz to get the 42 MHz, still resulting in almost -128 dBc/Hz at 42 MHz. Obviously filters will have to be used to get rid of the unwanted lower mixing products. Depending on the architecture used, as stated below, further multiplications will again decrease these numbers by 20logN. Filtering at the IF with a 250 to 500 Hz filter is not going to do anything to the 100 Hz numbers. I assume the mode of communications here is CW, hence the narrow filter at IF. 73 - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: Sunday, September 19, 2010 2:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OT: xtal osc PN francesco messineo wrote: > Hi Mike, > > as I said, current plans are for a few frequencies in the 20-50 MHz > range. The current project needs 20, 22 and 42 MHz oscillators. > But you're multiplying that up, it will be 20log(N) worse... _______________________________________________ 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.
