Hi Dave, very good question, for up-conversion it almost always pays off to use the highest frequency possible in my opinion. The reason is that you get a noise increase of 20log(n/m) when up-converting. So say you have two references, one at 10MHz and one at 100MHz. Say both have a noise floor or -160dBc which is realistic. If you up-convert the 10MHz noise floor to 1GHz by using a harmonic converter with very wide BW rather than a PLL with limited BW, then the resulting 1GHz noisefloor would theoretically be 40dB higher from the 10MHz source or -120dBc. That's not very good. If you upconvert the 100MHz source, the noise floor would be 20dB better, or 140dBc. For up-conversion using a PLL with limited bandwidth this would not hold true. Only the noise within the BW would be up-converted. So to answer your question: its tough to say if a 10MHz or 20MHz source would be better. However many oscillator vendors use the same crystal for 20MHz and 10MHz TCXO parts, and simply do an internal divide-by-2 inside the TCXO to get 10MHz from a 20MHz crystal! In that case you would save yourself one processing step when going from 20MHz instead of 10MHz, so theoretically the 20MHz part would be the one to use. Another consideration could be that at 10MHz you have a huge number of beating noise sources all around in a typical lab, the 10MHz short wave transmission from Colorado, other test equipment, etc etc, and at 20MHz you have much less noise that could beat with your source, so that would be another reason to use 20MHz if you can in my opinion. Bye, Said In a message dated 11/20/2014 13:40:37 Pacific Standard Time, drkirkby@kirkbymicrowave.co.uk writes: Said, For a general purpose lab source, to feed things like * 22 GHz spectrum analyzer * 4.5 and 20 GHz signal generators * 3 and 20 GHz VNAs * 20 or 40 GHz frequency counter (I'm just looking to buy one) what would you think is the best one to get - 10 or 20 MHz ? Or toss a coin? Dave Dr. David Kirkby Ph.D CEng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK. Registered in England and Wales, company number 08914892. http://www.kirkbymicrowave.co.uk/ Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please) On 20 November 2014 20:32, S. Jackson via time-nuts <time-nuts@febo.com> wrote: > Hello everyone, > > after what must have been the longest thread in T-nuts history its almost > all quiet today. I am going to take advantage of that and announce some > good news: > > Its a miracle: the 10MHz DIP-14 TCXOs for the LTE-Lite came in weeks ahead > of schedule from the factory! And they work very well. > > We will thus be shipping out the 10MHz LTE-Lite eval boards in the next > couple of working days. There are still a number left for sale on Ebay > (search for "LTE Lite GPSDO"), so if you were hesitant to get one due to the long > lead-time, then now is your chance. > > Also, after being in time nuts hands for almost a week I am surprised > there are very few mails, questions, or comments about the 20MHz boards, and we > have received almost no feedback on Ebay :( I hope that is a good sign. > > Bye, > Said > > > > _______________________________________________ > 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.