Re: [time-nuts] HF frequency counting receiver
Hi Yes, indeed doppler is problem. It is not a un-solvable problem. That’s why you need the long audio records to look at. That’s why you go a bit crazy looking at giant long FFT’s. The next layer to it is that your receiver has to stay on that signal for the entire duration of the test. If you want to track multiple signals on multiple bands …. you need multiple receivers. That or you need an SDR that captures the entire HF spectrum and processes out what you need. My solution was big stacks of R-1051’s, RF-550’s and RF-590’s. Redundancy is also a good idea. Lots of fun. Bob > On Jun 20, 2016, at 4:44 PM, Graham / KE9H wrote: > > Most of the folks doing the FMT these days use some sort of audio > spectrum analyzer program and estimate the frequency using that. > > Or use the audio spectrum analyzer to measure the difference between > the frequency being measured and the precision reference. You are > correct, it is usually not a classic counter. > > > You need a good reference to calibrate the frequency of your receiver - > depending on its design, you might just be able to measure your 10MHz > reference > to figure out the offset for your receiver, and if it's stable over the > time required, you're good to go. > > Well, even if the synthesizer is GPSDO referenced and locked, a digital > synthesizer > will have a minimum step size or resolution that it can generate. > You might not be able to hear it with your ear, but it is there. > For instance a DDS based synthesizer with a 32 bit tuning word and a 200 MHz > sampling clock will have a step size of 46 milliHertz. > So when you enter a decimal frequency into the synthesizer, you get the > closest frequency it can generate, which can have an error of up to +/- 23 > milliHertz. And the actual error versus frequency entered breaks into sort > of > a Moire pattern if you plot it. The errors are deterministic, but a user > normally does not have the > information to figure them out. > > The ionospheric Doppler will spread the signal a few tenths of a Hz, YES. > > so getting millihertz is more random luck of the draw. NO, > it is all about how good your averaging method/strategy is, over the period > of the test measurement. > A lot of the Doppler error can be averaged out. > Some of it is an actual net vertical movement of the reflection point, as > you said, worst at sunrise/sunset. > > Look at the scores/accuracy for some of the recent frequency measurement > tests. > > --- Graham > > == > > On Mon, Jun 20, 2016 at 12:16 PM, jimlux wrote: > >> On 6/20/16 7:51 AM, Nick Sayer via time-nuts wrote: >> >>> I'm considering taking a shot at the next ARRL frequency measurement >>> contest. >>> >>> The assumption going in is that the signal is CW, with at least a >>> half minute or so of just solid "on" at one point or another and that >>> reception is reasonably good. >>> >>> I've got a good TIA and excellent references, but that's the easy >>> part, it seems to me. It seems to me that what I really need to do is >>> make a synthesized heterodyne receiver that can present an accurately >>> tuned RF band pass - say, 10 kHz wide with the synthesizer set for 5 >>> kHz steps - to the TIA, with some manually tunable high-pass and >>> low-pass filtering to isolate the signal of interest. If the mixer >>> got its LO from a synthesizer with a GPSDO reference, it seems to me >>> that you could then measure the frequency of the signal of interest >>> (now an audio frequency, so you can listen to it too) with the TIA >>> (also getting the GPSDO reference) and then do simple math to arrive >>> at the actual RF frequency. >>> >>> Anybody have any thoughts? >>> >>> >> Most of the folks doing the FMT these days use some sort of audio >> spectrum analyzer program and estimate the frequency using that. >> >> >> The signal isn't very high SNR (unless you're in Newington and they are >> radiating from W1AW) - I'm not sure a narrow band filter followed by >> a counter would be the best way to go. >> >> You need a good reference to calibrate the frequency of your receiver - >> depending on its design, you might just be able to measure your 10MHz >> reference to figure out the offset for your receiver, and if it's stable >> over the time required, you're good to go. >> >> The ionospheric Doppler will spread the signal a few tenths of a Hz, so >> getting millihertz is more random luck of the draw. >> >> >> I note also that the last ARRL FMT ran at 10PM EDT with a transmitter in >> California (where it was 7PM).. this is a particularly BAD time of day to >> do the test, because the ionosphere is changing effective height and >> attenuation so it greatly penalizes folks who are relying on skywave >> propagation. >> >> You can practice using WWV/WWVH, by the way.. nice AM signal with a good >> carrier. >> >> >> >> >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go
Re: [time-nuts] HF frequency counting receiver
On 6/20/16 1:44 PM, Graham / KE9H wrote: The ionospheric Doppler will spread the signal a few tenths of a Hz, YES. so getting millihertz is more random luck of the draw. NO, it is all about how good your averaging method/strategy is, over the period of the test measurement. A lot of the Doppler error can be averaged out. Some of it is an actual net vertical movement of the reflection point, as you said, worst at sunrise/sunset. Look at the scores/accuracy for some of the recent frequency measurement tests. You'd need to look at a lot of measurements to see whether the winner just got lucky. Looking at the 80m results and only taking the results that are within a few Hz to remove outliers (N=93), the mean was 3,598,357.22 Hz with SD = 0.405 Hz. The actual frequency was 3,598,357.16, so the mean was about 0.1 Hz away from the actual frequency.. I'd say the "winner" got there by chance. In fact, if we do a standard test of significance, the 352.22 is not different from 357.16 at the P<0.05 level (which is pretty crummy).. Beyond that, ionospheric frequency shift might be something where averaging doesn't help. It depends on the propagation path uncertainty vs time. If it's long term stable, then averaging will help. However, I'm not sure the ionosphere is long term stable: the ionosphere literature seems to show that phase variation at UHF frequencies (150 MHz) has a 1/f^3 characteristic. I'm sure that can be turned into an equivalent frequency stability/phase noise, and in turn, into an AVAR type metric. ___ 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.
Re: [time-nuts] HF frequency counting receiver
http://www.cliftonlaboratories.com/off-the-air_frequency_measurement.htm If you peruse http://www.b4h.net/fmt/fmtresults201204.php you will see that HP3336A's also feature regularly. On Jun 21, 2016, at 4:52 AM, Pete Lancashire wrote: > Never tried it but a Selective Level Meter aka HP 3586A/B/C ? > ___ 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.
Re: [time-nuts] HF frequency counting receiver
On 6/20/2016 11:18 AM, Mark Spencer wrote: I am quite convinced that HF Doppler shift is a real issue at times. Absolutely true Mark. I spent some time looking at this way back when and it is quite possible to observe (in Southern Calfornia) transitory phase shifts on the 10 MHz signal from WWV of more than 360 degrees. Some times of day are worse than others. In 2003, the last time I bothered with the FMT and then it was from a signal at the ARRL, i.e. right across the country from me, I was able to get within 0.1Hz using nothing more than a 1Hz tuning receiver with external reference and a 100 kHz IF output which I compared with another output from the Standard on an oscilloscope. But this did involve a lot of visual averaging and estimation on the 'scope as the apparent received frequency varied. This was the usual method of measuring frequencies off air in the day. Most more "modern" FMT approaches have been using sound cards, but I've no experience of these. Whatever method is used once you have any ionospheric reflections then you will start to see phase shifts which will be what limits your accuracy. Dan ac6ao ___ 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.
Re: [time-nuts] HF frequency counting receiver
Most of the folks doing the FMT these days use some sort of audio spectrum analyzer program and estimate the frequency using that. Or use the audio spectrum analyzer to measure the difference between the frequency being measured and the precision reference. You are correct, it is usually not a classic counter. You need a good reference to calibrate the frequency of your receiver - depending on its design, you might just be able to measure your 10MHz reference to figure out the offset for your receiver, and if it's stable over the time required, you're good to go. Well, even if the synthesizer is GPSDO referenced and locked, a digital synthesizer will have a minimum step size or resolution that it can generate. You might not be able to hear it with your ear, but it is there. For instance a DDS based synthesizer with a 32 bit tuning word and a 200 MHz sampling clock will have a step size of 46 milliHertz. So when you enter a decimal frequency into the synthesizer, you get the closest frequency it can generate, which can have an error of up to +/- 23 milliHertz. And the actual error versus frequency entered breaks into sort of a Moire pattern if you plot it. The errors are deterministic, but a user normally does not have the information to figure them out. The ionospheric Doppler will spread the signal a few tenths of a Hz, YES. so getting millihertz is more random luck of the draw. NO, it is all about how good your averaging method/strategy is, over the period of the test measurement. A lot of the Doppler error can be averaged out. Some of it is an actual net vertical movement of the reflection point, as you said, worst at sunrise/sunset. Look at the scores/accuracy for some of the recent frequency measurement tests. --- Graham == On Mon, Jun 20, 2016 at 12:16 PM, jimlux wrote: > On 6/20/16 7:51 AM, Nick Sayer via time-nuts wrote: > >> I'm considering taking a shot at the next ARRL frequency measurement >> contest. >> >> The assumption going in is that the signal is CW, with at least a >> half minute or so of just solid "on" at one point or another and that >> reception is reasonably good. >> >> I've got a good TIA and excellent references, but that's the easy >> part, it seems to me. It seems to me that what I really need to do is >> make a synthesized heterodyne receiver that can present an accurately >> tuned RF band pass - say, 10 kHz wide with the synthesizer set for 5 >> kHz steps - to the TIA, with some manually tunable high-pass and >> low-pass filtering to isolate the signal of interest. If the mixer >> got its LO from a synthesizer with a GPSDO reference, it seems to me >> that you could then measure the frequency of the signal of interest >> (now an audio frequency, so you can listen to it too) with the TIA >> (also getting the GPSDO reference) and then do simple math to arrive >> at the actual RF frequency. >> >> Anybody have any thoughts? >> >> > Most of the folks doing the FMT these days use some sort of audio > spectrum analyzer program and estimate the frequency using that. > > > The signal isn't very high SNR (unless you're in Newington and they are > radiating from W1AW) - I'm not sure a narrow band filter followed by > a counter would be the best way to go. > > You need a good reference to calibrate the frequency of your receiver - > depending on its design, you might just be able to measure your 10MHz > reference to figure out the offset for your receiver, and if it's stable > over the time required, you're good to go. > > The ionospheric Doppler will spread the signal a few tenths of a Hz, so > getting millihertz is more random luck of the draw. > > > I note also that the last ARRL FMT ran at 10PM EDT with a transmitter in > California (where it was 7PM).. this is a particularly BAD time of day to > do the test, because the ionosphere is changing effective height and > attenuation so it greatly penalizes folks who are relying on skywave > propagation. > > You can practice using WWV/WWVH, by the way.. nice AM signal with a good > carrier. > > > > > > > ___ > 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.
Re: [time-nuts] HF frequency counting receiver
> On Jun 20, 2016, at 12:52 PM, Bob Camp wrote: > > Hi > > The cheaters way is to simply use a fully synthesized radio tied to a known > reference frequency. Yeah, that’s what I’ve got in mind. Both the synthesized tuning LO and the second LO would be derived from an external 10 MHz standard. My thought is to make a 10 kHz passband tunable in 5 kHz steps. Now, designing a receiver may be biting off more than I can chew, but that’s what I was going to try. > Feed the output into one channel of a sound card. Feed > the other channel of the sound card with a known frequency tone. Post process > it to death with your choice of FFT programs. Well, using the same 10 MHz standard to make a 1 or 5 kHz tone (or both) should be easy. From what you and others have said, it sounds like trying to use a TIA to read the audio frequency is a non-starter. ___ 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.
Re: [time-nuts] HF frequency counting receiver
Hi The cheaters way is to simply use a fully synthesized radio tied to a known reference frequency. Feed the output into one channel of a sound card. Feed the other channel of the sound card with a known frequency tone. Post process it to death with your choice of FFT programs. Another approach is to use a synthesized generator. Feed an appropriate level tone into the antenna input of the radio through a combiner. Set it so that both it and the FMT signal are inside your passband. Some care should be taken to see that you do not radiate your test tone. If you are going to rig up something special … just do a SDR of some sort. The post processing is all the same once it gets to audio. The noise and fading are such that there is essentially no way to directly read the frequency. That was true back when I was within ground wave for the transmissions. It’s even more true if you don’t live next door to them RF wise. Bob > On Jun 20, 2016, at 10:51 AM, Nick Sayer via time-nuts > wrote: > > I'm considering taking a shot at the next ARRL frequency measurement contest. > > The assumption going in is that the signal is CW, with at least a half minute > or so of just solid "on" at one point or another and that reception is > reasonably good. > > I've got a good TIA and excellent references, but that's the easy part, it > seems to me. It seems to me that what I really need to do is make a > synthesized heterodyne receiver that can present an accurately tuned RF band > pass - say, 10 kHz wide with the synthesizer set for > 5 kHz steps - to the TIA, with some manually tunable high-pass and low-pass > filtering to isolate the signal of interest. If the mixer got its LO from a > synthesizer with a GPSDO reference, it seems to me that you could then > measure the frequency of the signal of interest (now an audio frequency, so > you can listen to it too) with the TIA (also getting the GPSDO reference) and > then do simple math to arrive at the actual RF frequency. > > Anybody have any thoughts? > > > Sent from my iPhone > ___ > 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.
Re: [time-nuts] HF frequency counting receiver
To echo the point that Jim Lux made in another post... I'm not sure how those of us who live an appreciable distance from the transmitters can expect to get mili hertz accuracy in light of the HF Doppler shift over long distance paths with restorting to tactics such as simultaneously monitoring another transmitter that has a precisely known frequency and is located near the target transmitter to determine what the Doppler shift is at a given point of time. (I'm not 100 percent sure this approach would work but it seems viable to me at first glance.) I've spent some quality time monitoring WWV, and have read various papers and I am quite convinced that HF Doppler shift is a real issue at times. All the best Mark S VE7AFZ Sent from my iPhone > On Jun 20, 2016, at 10:10 AM, Graham / KE9H wrote: > > You need to be able to measure frequency accurately in the milli-Hertz > range to be competitive in the frequency measuring contests. > > I doubt the Selective Voltmeters have that level of resolution. I think > they 'only' read to 0.1 Hz. > > --- Graham > > > > On Mon, Jun 20, 2016 at 11:52 AM, Pete Lancashire > wrote: > >> Never tried it but a Selective Level Meter aka HP 3586A/B/C ? >> >> On Mon, Jun 20, 2016 at 7:51 AM, Nick Sayer via time-nuts >> wrote: >>> I'm considering taking a shot at the next ARRL frequency measurement >> contest. >>> >>> The assumption going in is that the signal is CW, with at least a half >> minute or so of just solid "on" at one point or another and that reception >> is reasonably good. >>> >>> I've got a good TIA and excellent references, but that's the easy part, >> it seems to me. It seems to me that what I really need to do is make a >> synthesized heterodyne receiver that can present an accurately tuned RF >> band pass - say, 10 kHz wide with the synthesizer set for >>> 5 kHz steps - to the TIA, with some manually tunable high-pass and >> low-pass filtering to isolate the signal of interest. If the mixer got its >> LO from a synthesizer with a GPSDO reference, it seems to me that you could >> then measure the frequency of the signal of interest (now an audio >> frequency, so you can listen to it too) with the TIA (also getting the >> GPSDO reference) and then do simple math to arrive at the actual RF >> frequency. >>> >>> Anybody have any thoughts? >>> >>> >>> Sent from my iPhone >>> ___ >>> 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.
Re: [time-nuts] HF frequency counting receiver
On 6/20/16 10:10 AM, Graham / KE9H wrote: You need to be able to measure frequency accurately in the milli-Hertz range to be competitive in the frequency measuring contests. I doubt the Selective Voltmeters have that level of resolution. I think they 'only' read to 0.1 Hz. --- Gr And realistically, since the millihertz digits are pretty random from ionospheric propagation, it's sort of a lottery at that point. ___ 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.
Re: [time-nuts] HF frequency counting receiver
You need to be able to measure frequency accurately in the milli-Hertz range to be competitive in the frequency measuring contests. I doubt the Selective Voltmeters have that level of resolution. I think they 'only' read to 0.1 Hz. --- Graham On Mon, Jun 20, 2016 at 11:52 AM, Pete Lancashire wrote: > Never tried it but a Selective Level Meter aka HP 3586A/B/C ? > > On Mon, Jun 20, 2016 at 7:51 AM, Nick Sayer via time-nuts > wrote: > > I'm considering taking a shot at the next ARRL frequency measurement > contest. > > > > The assumption going in is that the signal is CW, with at least a half > minute or so of just solid "on" at one point or another and that reception > is reasonably good. > > > > I've got a good TIA and excellent references, but that's the easy part, > it seems to me. It seems to me that what I really need to do is make a > synthesized heterodyne receiver that can present an accurately tuned RF > band pass - say, 10 kHz wide with the synthesizer set for > > 5 kHz steps - to the TIA, with some manually tunable high-pass and > low-pass filtering to isolate the signal of interest. If the mixer got its > LO from a synthesizer with a GPSDO reference, it seems to me that you could > then measure the frequency of the signal of interest (now an audio > frequency, so you can listen to it too) with the TIA (also getting the > GPSDO reference) and then do simple math to arrive at the actual RF > frequency. > > > > Anybody have any thoughts? > > > > > > Sent from my iPhone > > ___ > > 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.
Re: [time-nuts] HF frequency counting receiver
On 6/20/16 7:51 AM, Nick Sayer via time-nuts wrote: I'm considering taking a shot at the next ARRL frequency measurement contest. The assumption going in is that the signal is CW, with at least a half minute or so of just solid "on" at one point or another and that reception is reasonably good. I've got a good TIA and excellent references, but that's the easy part, it seems to me. It seems to me that what I really need to do is make a synthesized heterodyne receiver that can present an accurately tuned RF band pass - say, 10 kHz wide with the synthesizer set for 5 kHz steps - to the TIA, with some manually tunable high-pass and low-pass filtering to isolate the signal of interest. If the mixer got its LO from a synthesizer with a GPSDO reference, it seems to me that you could then measure the frequency of the signal of interest (now an audio frequency, so you can listen to it too) with the TIA (also getting the GPSDO reference) and then do simple math to arrive at the actual RF frequency. Anybody have any thoughts? Most of the folks doing the FMT these days use some sort of audio spectrum analyzer program and estimate the frequency using that. The signal isn't very high SNR (unless you're in Newington and they are radiating from W1AW) - I'm not sure a narrow band filter followed by a counter would be the best way to go. You need a good reference to calibrate the frequency of your receiver - depending on its design, you might just be able to measure your 10MHz reference to figure out the offset for your receiver, and if it's stable over the time required, you're good to go. The ionospheric Doppler will spread the signal a few tenths of a Hz, so getting millihertz is more random luck of the draw. I note also that the last ARRL FMT ran at 10PM EDT with a transmitter in California (where it was 7PM).. this is a particularly BAD time of day to do the test, because the ionosphere is changing effective height and attenuation so it greatly penalizes folks who are relying on skywave propagation. You can practice using WWV/WWVH, by the way.. nice AM signal with a good carrier. ___ 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.
Re: [time-nuts] HF frequency counting receiver
Nick: You can do it this way, but it requires you to totally understand the mathematics and granularity of ALL of the frequency sources and synthesizers in the superhet receiver. And if there are any audio soundcards or sampling devices involved, the specifications and origin of the sampling clocks. If it is the USB clock in your computer, you can be pretty much screwed right there. These are generally not published by the manufacturers, so you will need a friend at the manufacturer to provide you this information. Or be ready to do a lot of reverse engineering. The typical RF frequency measurement system for off-the-air measurement only uses the superhet for signal reception, then adds a precision (GPSDO derived) local oscillator/signal source for which you totally understand the mathematics and granularity, because you built it yourself, and an audio counter that allows you to measure the audio difference between the signal to be measured, and the local precision reference that you inject. In this system, the absolute frequency of the superhet receiver is a "don't care". You just want to measure the difference between the signal to be measured and your local precision reference. --- Graham == On Mon, Jun 20, 2016 at 9:51 AM, Nick Sayer via time-nuts < time-nuts@febo.com> wrote: > I'm considering taking a shot at the next ARRL frequency measurement > contest. > > The assumption going in is that the signal is CW, with at least a half > minute or so of just solid "on" at one point or another and that reception > is reasonably good. > > I've got a good TIA and excellent references, but that's the easy part, it > seems to me. It seems to me that what I really need to do is make a > synthesized heterodyne receiver that can present an accurately tuned RF > band pass - say, 10 kHz wide with the synthesizer set for > 5 kHz steps - to the TIA, with some manually tunable high-pass and > low-pass filtering to isolate the signal of interest. If the mixer got its > LO from a synthesizer with a GPSDO reference, it seems to me that you could > then measure the frequency of the signal of interest (now an audio > frequency, so you can listen to it too) with the TIA (also getting the > GPSDO reference) and then do simple math to arrive at the actual RF > frequency. > > Anybody have any thoughts? > > > Sent from my iPhone > ___ > 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.
Re: [time-nuts] HF frequency counting receiver
Never tried it but a Selective Level Meter aka HP 3586A/B/C ? On Mon, Jun 20, 2016 at 7:51 AM, Nick Sayer via time-nuts wrote: > I'm considering taking a shot at the next ARRL frequency measurement contest. > > The assumption going in is that the signal is CW, with at least a half minute > or so of just solid "on" at one point or another and that reception is > reasonably good. > > I've got a good TIA and excellent references, but that's the easy part, it > seems to me. It seems to me that what I really need to do is make a > synthesized heterodyne receiver that can present an accurately tuned RF band > pass - say, 10 kHz wide with the synthesizer set for > 5 kHz steps - to the TIA, with some manually tunable high-pass and low-pass > filtering to isolate the signal of interest. If the mixer got its LO from a > synthesizer with a GPSDO reference, it seems to me that you could then > measure the frequency of the signal of interest (now an audio frequency, so > you can listen to it too) with the TIA (also getting the GPSDO reference) and > then do simple math to arrive at the actual RF frequency. > > Anybody have any thoughts? > > > Sent from my iPhone > ___ > 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] HF frequency counting receiver
I'm considering taking a shot at the next ARRL frequency measurement contest. The assumption going in is that the signal is CW, with at least a half minute or so of just solid "on" at one point or another and that reception is reasonably good. I've got a good TIA and excellent references, but that's the easy part, it seems to me. It seems to me that what I really need to do is make a synthesized heterodyne receiver that can present an accurately tuned RF band pass - say, 10 kHz wide with the synthesizer set for 5 kHz steps - to the TIA, with some manually tunable high-pass and low-pass filtering to isolate the signal of interest. If the mixer got its LO from a synthesizer with a GPSDO reference, it seems to me that you could then measure the frequency of the signal of interest (now an audio frequency, so you can listen to it too) with the TIA (also getting the GPSDO reference) and then do simple math to arrive at the actual RF frequency. Anybody have any thoughts? Sent from my iPhone ___ 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.
