I am surprised that no one has mentioned the idea of heterodyning a known frequency with the unknown to measure the unknown. I use a Minicircuits doubly balanced mixer fed on one port from a PTS160 synthesizer that is locked to 10 mhz. from a TrueTime xl-ak GPS locked receiver. The second port is fed by the unknown though an attenuator. The third port of the mixer gives me the sum and difference. If the difference is an audio note then a cheep but frequency locked counter will read out the difference or measure the period of the beat note which can be added to the frequency of the synthesizer. A program such as Lady Heather can also be used to determine the audio frequency to much less then sub-cycle accuracy. The only fly in the ointment is figuring out which side of the unknown the synthesizer is set to. Alternatively, the PTS160 with 0.1 cycle control can be set to nearly zero beat with the unknown. Then watching either lissajous or dual trace scope patterns and timing the beat notes one can get the unknown frequency very close. Al, retired, mostly AKA k9si

 On 27 April 2017 at 06:52 al wolfe <alw.k9si@gmail.com> wrote:

 I am surprised that no one has mentioned the idea of heterodyning a
 known frequency with the unknown to measure the unknown. I use a
 Minicircuits doubly balanced mixer fed on one port from a PTS160
 synthesizer that is locked to 10 mhz. from a TrueTime xl-ak GPS locked
 receiver. The second port is fed by the unknown though an attenuator.
 The third port of the mixer gives me the sum and difference. If the
 difference is an audio note then a cheep but frequency locked counter
 will read out the difference or measure the period of the beat note
 which can be added to the frequency of the synthesizer. A program such
 as Lady Heather can also be used to determine the audio frequency to
 much less then sub-cycle accuracy. The only fly in the ointment is
 figuring out which side of the unknown the synthesizer is set to.

 Alternatively, the PTS160 with 0.1 cycle control can be set to nearly
 zero beat with the unknown. Then watching either lissajous or dual
 trace scope patterns and timing the beat notes one can get the unknown
 frequency very close.

 Al, retired, mostly
 AKA k9si

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Use a USB or LSB mixer, it only requires a few more parts and a little ingenuity. Bruce > > On 27 April 2017 at 06:52 al wolfe <alw.k9si@gmail.com> wrote: > > I am surprised that no one has mentioned the idea of heterodyning a > known frequency with the unknown to measure the unknown. I use a > Minicircuits doubly balanced mixer fed on one port from a PTS160 > synthesizer that is locked to 10 mhz. from a TrueTime xl-ak GPS locked > receiver. The second port is fed by the unknown though an attenuator. > The third port of the mixer gives me the sum and difference. If the > difference is an audio note then a cheep but frequency locked counter > will read out the difference or measure the period of the beat note > which can be added to the frequency of the synthesizer. A program such > as Lady Heather can also be used to determine the audio frequency to > much less then sub-cycle accuracy. The only fly in the ointment is > figuring out which side of the unknown the synthesizer is set to. > > Alternatively, the PTS160 with 0.1 cycle control can be set to nearly > zero beat with the unknown. Then watching either lissajous or dual > trace scope patterns and timing the beat notes one can get the unknown > frequency very close. > > Al, retired, mostly > AKA k9si > > _______________________________________________ > 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. >

The heterodyne trick has been done before the first 'Modern' frequency counter the HP 5245 used plug ins to extend its range to 18 Ghz by doing exactly that. The plug in contained a tunable LO mixer and indicator to show tuning lock These were a pain to use but they beat the 'frequency meters' by a mile Content by Scott Typos by Siri > On Apr 26, 2017, at 2:52 PM, al wolfe <alw.k9si@gmail.com> wrote: > > such

Hi The heterodyne approach dates back at least into the 1930’s in general lab use. I’m sure it dates well before that on an experimental basis. The LM and BC-221 frequency meters are good examples of it’s use. Adding an “error multiplier” to the setup could give you a very impressive resolution. Accuracy (or course) still deepened on what you had as a standard driving the error multiplier. Bob > On Jun 8, 2017, at 8:35 AM, Scott McGrath <scmcgrath@gmail.com> wrote: > > The heterodyne trick has been done before the first > 'Modern' frequency counter the HP 5245 used plug ins to extend its range to 18 Ghz by doing exactly that. The plug in contained a tunable LO mixer and indicator to show tuning lock > > These were a pain to use but they beat the 'frequency meters' by a mile > > Content by Scott > Typos by Siri > >> On Apr 26, 2017, at 2:52 PM, al wolfe <alw.k9si@gmail.com> wrote: >> >> such > _______________________________________________ > 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.

Hi, Many modern counters use this trick too, but much more gift-wrapped, in that they themselves shift their oscillator to measure the shift and hence figure out which overtone is being used and hence derive the correct frequency. With HP5245 etc you had to do a little work on your own for post-processing. The same basic trick is also fundamental to frequency comb measurement of optical frequencies. Heterodyning remains one of several approaches to design high frequency counters. Cheers, Magnus On 06/08/2017 02:35 PM, Scott McGrath wrote: > The heterodyne trick has been done before the first > 'Modern' frequency counter the HP 5245 used plug ins to extend its range to 18 Ghz by doing exactly that. The plug in contained a tunable LO mixer and indicator to show tuning lock > > These were a pain to use but they beat the 'frequency meters' by a mile > > Content by Scott > Typos by Siri > >> On Apr 26, 2017, at 2:52 PM, al wolfe <alw.k9si@gmail.com> wrote: >> >> such > _______________________________________________ > 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. >