Re: [time-nuts] Building new pods for the Spectracom 8140 using modern components
Hi ….. a little elaboration ….. If you *don’t* terminate the main distribution line, it effectively acts as a great big antenna. It floods the lab area (or production floor or building …) with 10 MHz. I unfortunately have a lot of empirical data to back this up. It’s also worth using a “better” grade of coax for the distribution line (as opposed to Home Depot’s lowest cost spool …) for pretty much the same reason. One second ADEV on a typical pod is usually in the 2x10^-11 vicinity. Plenty good enough for driving test gear. Not quite up to acting as your ADEV reference in a DMTD. Bob > On Apr 27, 2019, at 12:25 PM, John Ackermann N8UR wrote: > > I have a large box of 8140 pods (well, I call them "taps"). They are quite > handy for stringing distribution points around a large room, provided > ultimate phase noise performance isn't required. > > You *don't* need an 8140 main box to use these. All the 8140 does is put 12V > DC bias on its output connectors, and the taps couple their power off the > coax with an RC choke. When I was using my setup, I built a bias-tee box > that was inserted right after the frequency source and that worked fine. > > However, one note: for best performance, you want to terminate the end of > the distribution line in 50 ohms, but since there's a DC voltage present, you > need to include a DC block (series capacitor) so you're not burning 3 watts > in the load. > > John > > On 4/27/19 10:17 AM, Julien Goodwin wrote: >> Slightly edited down from my blog, if you want the full thing with >> photos see: >> https://laptop006.livejournal.com/60862.html >> I've mentioned a bunch of times on the time-nuts list that I'm quite >> fond of the Spectracom 8140 system for frequency distribution. For those >> not familiar with it, it's simply running a 10MHz signal against a 12v >> DC power feed so that line-powered pods can tap off the reference >> frequency and use it as an input to either a buffer (10MHz output pods), >> decimation logic (1MHz, 100kHz etc.), or a full synthesizer (Versa-pods). >> It was only in October last year that I got a house frequency standard >> going using an old Efratom FRK-LN which now provides the reference; I'd >> use a GPSDO, but I live in a ground floor apartment without a usable sky >> view, this of course makes it hard to test some of the GPS projects I'm >> doing. Despite living in a tiny apartment I have test equipment in two >> main places, so the 8140 is a great solution to allow me to lock all of >> them to the house standard. >> Another benefit of the 8140 is that many modern pieces of equipment >> (such as my [HP/Agilent/]Keysight oscilloscope) have a single connector >> for reference frequency in/out, and should the external frequency ever >> go away it will switch back to its internal reference, but also send >> that back out the connector, which could lead to other devices sharing >> the same signal switching to it. The easy way to avoid that is to use a >> dedicated port from a distribution amplifier for each device like this, >> which works well enough until you have this situation in multiple locations. >> As previously mentioned the 8140 system uses pods to add outputs, while >> these pods are still available quite cheaply used on eBay (as of this >> writing, for as low as US$8, but ~US$25/pod has been common for a >> while), recently the cost of shipping to Australia has gone up to the >> point I started to plan making my own. >> By making my own pods I also get to add features that the original pods >> didn't have[1], I started with a quad-output pod with optional internal >> line termination. This allows me to have feeds for multiple devices with >> the annoying behaviour I mentioned earlier. The enclosure is a Pomona >> model 4656, with the board designed to slot in, and offer pads for the >> BNC pins to solder to for easy assembly. >> This pod uses a Linear Technologies (now Analog Devices) LTC6957 buffer >> for the input stage replacing a discrete transistor & logic gate >> combined input stage in the original devices. The most notable change is >> that this stage works reliably down to -30dBm input (possibly further, >> couldn't test beyond that), whereas the original pods stop working right >> around -20dBm. >> As it turns out, although it can handle lower input signal levels, in >> other ways including power usage it seems very similar. One notable >> downside is the chip tops out at 4v absolute maximum input, so a >> separate regulator is used just to feed this chip. The main regulator >> has also been changed from a 7805 to an LD1117 variant. >> On this version the output stage is the same TI 74S140 dual 4-input NAND >> gate as was used on the original pods, just in SOIC form factor. >> As with the next board there is one error on the board, the wire loop >> that forms the ground connection was intended to fit a U-type pin >> header, however the footprint I used on the boards was just too tight to
Re: [time-nuts] Building new pods for the Spectracom 8140 using modern components
I have a large box of 8140 pods (well, I call them "taps"). They are quite handy for stringing distribution points around a large room, provided ultimate phase noise performance isn't required. You *don't* need an 8140 main box to use these. All the 8140 does is put 12V DC bias on its output connectors, and the taps couple their power off the coax with an RC choke. When I was using my setup, I built a bias-tee box that was inserted right after the frequency source and that worked fine. However, one note: for best performance, you want to terminate the end of the distribution line in 50 ohms, but since there's a DC voltage present, you need to include a DC block (series capacitor) so you're not burning 3 watts in the load. John On 4/27/19 10:17 AM, Julien Goodwin wrote: Slightly edited down from my blog, if you want the full thing with photos see: https://laptop006.livejournal.com/60862.html I've mentioned a bunch of times on the time-nuts list that I'm quite fond of the Spectracom 8140 system for frequency distribution. For those not familiar with it, it's simply running a 10MHz signal against a 12v DC power feed so that line-powered pods can tap off the reference frequency and use it as an input to either a buffer (10MHz output pods), decimation logic (1MHz, 100kHz etc.), or a full synthesizer (Versa-pods). It was only in October last year that I got a house frequency standard going using an old Efratom FRK-LN which now provides the reference; I'd use a GPSDO, but I live in a ground floor apartment without a usable sky view, this of course makes it hard to test some of the GPS projects I'm doing. Despite living in a tiny apartment I have test equipment in two main places, so the 8140 is a great solution to allow me to lock all of them to the house standard. Another benefit of the 8140 is that many modern pieces of equipment (such as my [HP/Agilent/]Keysight oscilloscope) have a single connector for reference frequency in/out, and should the external frequency ever go away it will switch back to its internal reference, but also send that back out the connector, which could lead to other devices sharing the same signal switching to it. The easy way to avoid that is to use a dedicated port from a distribution amplifier for each device like this, which works well enough until you have this situation in multiple locations. As previously mentioned the 8140 system uses pods to add outputs, while these pods are still available quite cheaply used on eBay (as of this writing, for as low as US$8, but ~US$25/pod has been common for a while), recently the cost of shipping to Australia has gone up to the point I started to plan making my own. By making my own pods I also get to add features that the original pods didn't have[1], I started with a quad-output pod with optional internal line termination. This allows me to have feeds for multiple devices with the annoying behaviour I mentioned earlier. The enclosure is a Pomona model 4656, with the board designed to slot in, and offer pads for the BNC pins to solder to for easy assembly. This pod uses a Linear Technologies (now Analog Devices) LTC6957 buffer for the input stage replacing a discrete transistor & logic gate combined input stage in the original devices. The most notable change is that this stage works reliably down to -30dBm input (possibly further, couldn't test beyond that), whereas the original pods stop working right around -20dBm. As it turns out, although it can handle lower input signal levels, in other ways including power usage it seems very similar. One notable downside is the chip tops out at 4v absolute maximum input, so a separate regulator is used just to feed this chip. The main regulator has also been changed from a 7805 to an LD1117 variant. On this version the output stage is the same TI 74S140 dual 4-input NAND gate as was used on the original pods, just in SOIC form factor. As with the next board there is one error on the board, the wire loop that forms the ground connection was intended to fit a U-type pin header, however the footprint I used on the boards was just too tight to allow the pins through, so I've used some thin bus wire instead. The second major variant I designed was a combo version, allowing sine & square outputs by just switching a jumper, or isolated[2] or line-regenerator (8040TA from Spectracom) versions with a simple sub-board containing just an inductor (TA) or 1:1 transformer (isolated). This is the second revision of that board, where the 74S140 has been replaced by a modern TI 74LVC1G17 buffer. This version of the pod, set for sine output, uses almost exactly 30mA of power (since both the old & new pods use linear supplies that's the most sensible unit), whereas the original pods are right around 33mA. The empty pods at the bottom-left are simply placeholders for 2 100 ohm resistors to add 50 ohm line termination if desired. The board fits into the Pomona 2390 "Size A"
Re: [time-nuts] Building new pods for the Spectracom 8140 using modern components
Good work on the project, Julien. I have a couple of the 8140 distribution amps, one of which I use in my shop. Instead of buying the line taps that are supposed to be used with the 8140, I just disabled the 12V riding on the output signal coming out of the amp. I have another unit as a spart, but not modified (yet). Your pods seem to be good replacements for the line taps... Do you plan to publish the details of your pods (schematics & PCB design)? I might be tempted to build a few for my own use. Thanks for posting your project. Nice work. Dave M Julien Goodwin wrote: Slightly edited down from my blog, if you want the full thing with photos see: https://laptop006.livejournal.com/60862.html I've mentioned a bunch of times on the time-nuts list that I'm quite fond of the Spectracom 8140 system for frequency distribution. For those not familiar with it, it's simply running a 10MHz signal against a 12v DC power feed so that line-powered pods can tap off the reference frequency and use it as an input to either a buffer (10MHz output pods), decimation logic (1MHz, 100kHz etc.), or a full synthesizer (Versa-pods). It was only in October last year that I got a house frequency standard going using an old Efratom FRK-LN which now provides the reference; I'd use a GPSDO, but I live in a ground floor apartment without a usable sky view, this of course makes it hard to test some of the GPS projects I'm doing. Despite living in a tiny apartment I have test equipment in two main places, so the 8140 is a great solution to allow me to lock all of them to the house standard. Another benefit of the 8140 is that many modern pieces of equipment (such as my [HP/Agilent/]Keysight oscilloscope) have a single connector for reference frequency in/out, and should the external frequency ever go away it will switch back to its internal reference, but also send that back out the connector, which could lead to other devices sharing the same signal switching to it. The easy way to avoid that is to use a dedicated port from a distribution amplifier for each device like this, which works well enough until you have this situation in multiple locations. As previously mentioned the 8140 system uses pods to add outputs, while these pods are still available quite cheaply used on eBay (as of this writing, for as low as US$8, but ~US$25/pod has been common for a while), recently the cost of shipping to Australia has gone up to the point I started to plan making my own. By making my own pods I also get to add features that the original pods didn't have[1], I started with a quad-output pod with optional internal line termination. This allows me to have feeds for multiple devices with the annoying behaviour I mentioned earlier. The enclosure is a Pomona model 4656, with the board designed to slot in, and offer pads for the BNC pins to solder to for easy assembly. This pod uses a Linear Technologies (now Analog Devices) LTC6957 buffer for the input stage replacing a discrete transistor & logic gate combined input stage in the original devices. The most notable change is that this stage works reliably down to -30dBm input (possibly further, couldn't test beyond that), whereas the original pods stop working right around -20dBm. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building new pods for the Spectracom 8140 using modern components
On 4/27/2019 7:17 AM, Julien Goodwin wrote: This is the second revision of that board, where the 74S140 has been replaced by a modern TI 74LVC1G17 buffer. This version of the pod, set for sine output, uses almost exactly 30mA of power (since both the old & Does anyone have any phase noise measurements of the 74LVC1G17 et al? Rick ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Query about NRL Canvas source?
On 4/27/19 5:31 AM, AC0XU (Jim) wrote: Does anyone know how to obtain the NRL Canvas (clock analsis) software? The widely published link https://goby.nrl.navy.mil/canvas/ appears to be broken. Thanks! You could always email Ken Senior at NRL and ask him. ken.sen...@nrl.navy.mil A bit of browsing around shows that NRL has somewhat reorganized since the CANVAS paper was published in 2005 (there's no Space Applications Branch any more, for instance), and the "download open source software" function may have been centralized in some sort of "US government" portal. The distribution mechanism moves around at JPL and NASA, I see no reason why it wouldn't also occur at NRL - and in none of these cases is it trivial to find. For some reason, they set up websites and assume people will know that's the URL by magic, since it doesn't always get indexed by Google. for instance https://code.nasa.gov/ purports to be a repository of NASA open source software, but there's plenty of other places to go look. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Query about NRL Canvas source?
CANVAS is apparently northern hemisphere specific. I just asked and was allowed to download CANVAS including source code Bruce > On 28 April 2019 at 01:21 Bob kb8tq wrote: > > > Hi > > Just to confirm - it seems to be broken from here as well. > > Bob > > > On Apr 27, 2019, at 7:31 AM, AC0XU (Jim) wrote: > > > > Does anyone know how to obtain the NRL Canvas (clock analsis) software? > > The widely published link > > > > https://goby.nrl.navy.mil/canvas/ > > > > appears to be broken. Thanks! > > > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Building new pods for the Spectracom 8140 using modern components
Slightly edited down from my blog, if you want the full thing with photos see: https://laptop006.livejournal.com/60862.html I've mentioned a bunch of times on the time-nuts list that I'm quite fond of the Spectracom 8140 system for frequency distribution. For those not familiar with it, it's simply running a 10MHz signal against a 12v DC power feed so that line-powered pods can tap off the reference frequency and use it as an input to either a buffer (10MHz output pods), decimation logic (1MHz, 100kHz etc.), or a full synthesizer (Versa-pods). It was only in October last year that I got a house frequency standard going using an old Efratom FRK-LN which now provides the reference; I'd use a GPSDO, but I live in a ground floor apartment without a usable sky view, this of course makes it hard to test some of the GPS projects I'm doing. Despite living in a tiny apartment I have test equipment in two main places, so the 8140 is a great solution to allow me to lock all of them to the house standard. Another benefit of the 8140 is that many modern pieces of equipment (such as my [HP/Agilent/]Keysight oscilloscope) have a single connector for reference frequency in/out, and should the external frequency ever go away it will switch back to its internal reference, but also send that back out the connector, which could lead to other devices sharing the same signal switching to it. The easy way to avoid that is to use a dedicated port from a distribution amplifier for each device like this, which works well enough until you have this situation in multiple locations. As previously mentioned the 8140 system uses pods to add outputs, while these pods are still available quite cheaply used on eBay (as of this writing, for as low as US$8, but ~US$25/pod has been common for a while), recently the cost of shipping to Australia has gone up to the point I started to plan making my own. By making my own pods I also get to add features that the original pods didn't have[1], I started with a quad-output pod with optional internal line termination. This allows me to have feeds for multiple devices with the annoying behaviour I mentioned earlier. The enclosure is a Pomona model 4656, with the board designed to slot in, and offer pads for the BNC pins to solder to for easy assembly. This pod uses a Linear Technologies (now Analog Devices) LTC6957 buffer for the input stage replacing a discrete transistor & logic gate combined input stage in the original devices. The most notable change is that this stage works reliably down to -30dBm input (possibly further, couldn't test beyond that), whereas the original pods stop working right around -20dBm. As it turns out, although it can handle lower input signal levels, in other ways including power usage it seems very similar. One notable downside is the chip tops out at 4v absolute maximum input, so a separate regulator is used just to feed this chip. The main regulator has also been changed from a 7805 to an LD1117 variant. On this version the output stage is the same TI 74S140 dual 4-input NAND gate as was used on the original pods, just in SOIC form factor. As with the next board there is one error on the board, the wire loop that forms the ground connection was intended to fit a U-type pin header, however the footprint I used on the boards was just too tight to allow the pins through, so I've used some thin bus wire instead. The second major variant I designed was a combo version, allowing sine & square outputs by just switching a jumper, or isolated[2] or line-regenerator (8040TA from Spectracom) versions with a simple sub-board containing just an inductor (TA) or 1:1 transformer (isolated). This is the second revision of that board, where the 74S140 has been replaced by a modern TI 74LVC1G17 buffer. This version of the pod, set for sine output, uses almost exactly 30mA of power (since both the old & new pods use linear supplies that's the most sensible unit), whereas the original pods are right around 33mA. The empty pods at the bottom-left are simply placeholders for 2 100 ohm resistors to add 50 ohm line termination if desired. The board fits into the Pomona 2390 "Size A" enclosures, or for the isolated version the Pomona 3239 "Size B". This is the reason the BNC connectors have to be extended to reach the board, on the isolated boxes the BNC pins reach much deeper into the enclosure. If the jumpers were removed, plus the smaller buffer it should be easy to fit a pod into the Pomona "Miniature" boxes too. I was also due to create some new personal businesscards, so I arranged the circuit down to a single layer (the only jumper is the requirement to connect both ground pins on the connectors) and merged it with some text converted to KiCad footprints to make a nice card on some 0.6mm PCBs. The paper on that photo is covering the link to the build instructions, which weren't written at the time (they're *mostly* done now, I may update this post with the link later).
Re: [time-nuts] Query about NRL Canvas source?
Hi Just to confirm - it seems to be broken from here as well. Bob > On Apr 27, 2019, at 7:31 AM, AC0XU (Jim) wrote: > > Does anyone know how to obtain the NRL Canvas (clock analsis) software? The > widely published link > > https://goby.nrl.navy.mil/canvas/ > > appears to be broken. Thanks! > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
