Hi Put an L network in front of a biased NC7SZ04 running off of 5V and you should get a floor that’s ~ -170 dbc/Hz at 10 MHz. $0.34 each at quantity =1 at Mouser. The L network is set up to “what ever it takes” to give you 5V p-p on the gate input. The load termination on the L acts as the 50 ohm load for the oscillator.
Bob On Jul 29, 2014, at 8:54 AM, br...@ko4bb.com wrote: > I merely used the evaluation board which has a capacitively coupled input. > The transformer coupled input circuit using a 1:4 (turns ratio) step up > transformer > as depicted on the datasheet should reduce the PN floor by at least 3dB for > 10MHz input. > > Bruce >> On July 29, 2014 at 7:30 AM "David C. Partridge" >> <david.partri...@perdrix.co.uk> wrote: >> >> >> Bruce, >> >> Thank you, that was very useful information. If I ever do a re-spin of the >> divider I will likely use the LTC6957-3 or -4 instead of the ADCMP600 (I >> would need interest for at least 40 boards to be able to do this at anything >> like an economic price). >> >> Will you be putting the full details of the circuit you used up on Didier's >> web site? Did you use a transformer based circuit similar to Design Note >> 514 or just an input capacitor? >> >> Regards, >> David Partridge >> -----Original Message----- >> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >> Behalf Of br...@ko4bb.com >> Sent: 29 July 2014 12:00 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Sine to square wave converter Phase Noise >> >> Sorry, I meant the LTC6957-4 of course._SELA = l FILTA = L FILTB = H ie an >> input stage BW of 160MHz as recommended for a 10MHz + 10dBm input. >> >> Input for the HX4210 was +14dBm. >> >> Comparator was that used in David Partridge's programmable divider (includes >> the >> 74AC04 buffers). >> >> Bruce >> >>> On July 29, 2014 at 5:37 AM Magnus Danielson >>> <mag...@rubidium.dyndns.org> >>> wrote: >>> >>> >>> You alternate LTC7957-4 and LTC6957-4 and it is only the later that >> exists. >>> >>> The LTC6957-4 has a single-stage amplifier stage input, with somewhat >>> programmable bandwidth. I assume you used the 50 MHz BW setting. >>> >>> Cheers, >>> Magnus >>> >>> On 07/29/2014 10:55 AM, br...@ko4bb.com wrote: >>>> Recently I have been comparing the phase noise of the HOlzworth >>>> HX4210 and the LTC7957-4. >>>> I have found that the performance of these devices is comparable >>>> with a 10MHz sinewave input with a PN noise floor below -160dBc/Hz. >>>> For offsets below 100Hz the LTC6957-4 is quieter and for offsets >>>> below 50Hz or so is lower than that of my measurement setup. >>>> I merely mounted the LTC evaluation board in a diecast metal box to >>>> reduce the effect of air currents on the LTC7957-4 and used an ultra >>>> low noise 3.3V power supply (Abracon) to minimise the power supply >>>> contribution to the measured phase noise. >>>> Achieving a phase noise performance equal to that on the datasheet >>>> was relatively easy. >>>> In fact for low offsets the phase noise is lower than that shown on >>>> the datasheet. >>>> >>>> I've also measured the phase noise of a comparator based sine to >>>> CMOS converter and its PN floor is about 20dB higher than that of >>>> the LTC6957. >>>> On completion of measurements PN plots for the various sine to >>>> square conveters tested will be added to the web pages I maintain on >>>> Didiers site.. >>>> >>>> >>>> Bruce >>>> _______________________________________________ >>>> 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. >> _______________________________________________ >> 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. _______________________________________________ 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.