Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier?
On 7 Jan 2015 01:24, Charles Steinmetz csteinm...@yandex.com wrote: Dave wrote: At 50 MHz, the loss from the common port is 12.8 dB, and the isolation between two ports sets of ports is either 38 or 48 dB To get the worst-case output-to-output isolation, you need to test two output ports that are electrically adjacent (i.e., that share the same last 2:1 splitter, assuming that the 1:16 is a hierarchy of 1:2 splitters -- which is the case with the multi-output splitters I'm familiar with). You may already have found an electrically-adjacent pair (ports 7 and 8), but to be absolutely sure, you would need to repeat the test from one output to each of the 15 others (or find a full internal connection diagram, which does not seem to be on the datasheet). IIRC the odd port numbers are on one row, and the evens on the other. I found the highest isolation was between a port at the bottom and one at the top, which I assume is two splitters. I wouldn't bother retesting with out-of-band signals, but when you test at 10MHz it is something to think about. Yes, but I was aware of this, and that's why I got two different isolation figures. Another issue I thought of later, is that the reflection coefficient of all the open ports will be the same, as there's virtually no phase difference between the output terminals. If it was used as a distribution amplifier, that would no longer be the case. Potentially that could produce issues. Anyway, as I said it was just a quick test with suboptimal equipment used. But later I will perform a more thorough test with more suitable test equipment. Dave ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
On 8 January 2015 at 10:03, Charles Steinmetz csteinm...@yandex.com wrote: Dave wrote: Yes, but I was aware of this, and that's why I got two different isolation figures. What I was pointing out is that there will be *4* different isolation figures from any one output port, not just two. The lowest will be to the one electrically adjacent output, next (a bit higher) will be to two outputs at one remove, then (a bit higher yet) to four outputs twice removed, and finally (the highest) to eight outputs thrice removed (these eight are the ones you are calling on the other 1:8 splitter). Perhaps a diagram is in order (see below). Each dot represents a 1:2 splitter. (I've drawn only 1:8. A 1:16 is just this plus another 1:8, connected to the two outputs of another 1:2 splitter.) To find the worst case output-to-output isolation, you need to identify two electrically adjacent output ports -- either by measurement or from the manufacturer's published data. Best regards, Charles The Minicircuits data sheet http://194.75.38.69/pdfs/ZFSC-16-3.pdf basically shows there are two different isolation values, which it calls adjacent and opposite. These are typically 32 and 48 dB @ 10 MHz. I had a quick play yesterday, almost randomly putting the two BNC connectors in different sockets, and there does appear to be only two values of isolation values. What I did notice though is that if the common port is not terminated properly, that dramatically changes the isolation. That might be an issue, as I don't know what the return loss (S22) of the amplifier will be, although that is something I can measure. I need to order up a keyboard and mouse, and then I can use this Agilent N3383A VNA properly. Then I'll be able to make measurements at 10 MHz. (I bought the thing, then sold it a week later to a friend's company. He is working in Singapore, so he said I can borrow it until he gets back. His contract ends in July, but it might be extended, so this is a semi-permanent fixture here! Where else could you hire a 9 GHz VNA for 9 months for free?) If there was a design for an isolation amplifier around with a PCB available that worked well, I would build it. But for now at least, this might be good enough for what I want, which is basically to ensure my spectrum analyzer, signal generators have a common frequency reference. I don't think I have a need for great isolation, as I don't intend this to be used for the sort of precision measurement time-nuts do. BTW, I was looking at the design someone posted for one which used a discrete transistor and transformer. I forget which transistor it was, but I could get 100 delivered from China for £1.00 (about $1.60)!! I would not buy from China via eBay however, as the chances of them being original transistors are pretty remote, so I doubt their characteristics would be like those used to model that design. The transistors are only £0.07 from Farnell, so buying them is easy cheap enough. I just don't fancy the hassle of making a PCB if this 16-way splitter will do. Dave ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Charles is absolutely correct this is what I have seen in these large splitters. I have a really nice one that you can take the cover off and look. Lots of screws. Regards Paul WB8TSL On Thu, Jan 8, 2015 at 5:03 AM, Charles Steinmetz csteinm...@yandex.com wrote: Dave wrote: Yes, but I was aware of this, and that's why I got two different isolation figures. What I was pointing out is that there will be *4* different isolation figures from any one output port, not just two. The lowest will be to the one electrically adjacent output, next (a bit higher) will be to two outputs at one remove, then (a bit higher yet) to four outputs twice removed, and finally (the highest) to eight outputs thrice removed (these eight are the ones you are calling on the other 1:8 splitter). Perhaps a diagram is in order (see below). Each dot represents a 1:2 splitter. (I've drawn only 1:8. A 1:16 is just this plus another 1:8, connected to the two outputs of another 1:2 splitter.) To find the worst case output-to-output isolation, you need to identify two electrically adjacent output ports -- either by measurement or from the manufacturer's published data. Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Dave wrote: Yes, but I was aware of this, and that's why I got two different isolation figures. What I was pointing out is that there will be *4* different isolation figures from any one output port, not just two. The lowest will be to the one electrically adjacent output, next (a bit higher) will be to two outputs at one remove, then (a bit higher yet) to four outputs twice removed, and finally (the highest) to eight outputs thrice removed (these eight are the ones you are calling on the other 1:8 splitter). Perhaps a diagram is in order (see below). Each dot represents a 1:2 splitter. (I've drawn only 1:8. A 1:16 is just this plus another 1:8, connected to the two outputs of another 1:2 splitter.) To find the worst case output-to-output isolation, you need to identify two electrically adjacent output ports -- either by measurement or from the manufacturer's published data. Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Hi, I was doing some phase noise measurements today at a friends place. The Rapco 1804M was about -110 dBc/Hz at 10 kHz. It was 30 dB higher up from the HP5065A, which was some 10 dB higher than the BVA. On the other hand, when viewing the ADEV and TDEV, it became apparent that the Rapco has around 1 ps RMS noise at 1 s, and few counters will be affected by that noise. Just to put it in context. So, one should at least ponder about where the noise contributions is and what value it brings to go for a quieter distribution amp, and for what in (additional) cost. Cheers, Magnus On 01/06/2015 01:59 AM, Bob Camp wrote: Hi Any time you run into terms like “low noise” it pays to think about what that means to you and your system. A quick scan of the posts here over the years will show that different definitions of low noise do exist. The same is true of system requirements. An offset that matters to one may have no impact at all on another system. In some cases -155 dbc/Hz at 10KHz or 100 KHz is “low noise”. In other cases “low noise” is -180 dbc/Hz. In either case, *delivering* a clean signal without spurs and crud is far from simple. In many long cable run cases, the cost of fancy cables, high performance magnetics, and all the other “stuff” is more than the cost of simply locking up a quiet oscillator on the end of a “dirty” cable. I don’t think I’ve ever seen a setup that tries / needs to “distribute” -170 dbc/Hz signals over anything bigger than a rack. I’ve seen *lots* of systems that regenerate those sort of signals many times over (= in many different boxes) to get around distributing them. Bob On Jan 5, 2015, at 2:15 PM, Tom Knox act...@hotmail.com wrote: Happy New Years All! I have seen a number of discussions on various approaches to distribution amps discussed on Time-Nuts ranging from DYI to products intended for Video. I thought I my weigh in with one point of interest; It seems like long term performance is pretty easy, but a low phase noise solution is quite a different story. Looking at the number of application specific products from MicroSemi/Symmetricom and other manufactures claimed and even more so real world specs vary a great deal so apparently it s not easy to just throw something together with great or even good close in phase noise. So depending on your labs direction in the future it may be worth researching and investing in an application specific distribution amp. I like the MicroSemi 4036B but there are a number of very good products out there on the surplus market selling for a small fraction of their original cost. Cheers; Thomas Knox From: bill.ric...@verizon.net To: time-nuts@febo.com Date: Sun, 4 Jan 2015 08:29:34 -0500 Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier? A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm F type with an adapter. Maybe that combination would produce too much garbage. 73, Bill, WA2DVU Cape May --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Good point Bob, in my humble opinion Low Noise is about -115 @ 1 Hz dropping to about -165 @ 10KHz for 5 MHz about 3dB higher for 10MHz. Which from my testing will tax the noise floors of a fair number of application specific products. It is true that most of these distribution amps sold today were designed at least a decade ago, so there may be chips today that can meet or exceed those products on paper for DIY projects but it will still be a challenge for most of us. Thanks for your input Thomas Knox From: kb...@n1k.org Date: Mon, 5 Jan 2015 19:59:39 -0500 To: time-nuts@febo.com Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier? Hi Any time you run into terms like “low noise” it pays to think about what that means to you and your system. A quick scan of the posts here over the years will show that different definitions of low noise do exist. The same is true of system requirements. An offset that matters to one may have no impact at all on another system. In some cases -155 dbc/Hz at 10KHz or 100 KHz is “low noise”. In other cases “low noise” is -180 dbc/Hz. In either case, *delivering* a clean signal without spurs and crud is far from simple. In many long cable run cases, the cost of fancy cables, high performance magnetics, and all the other “stuff” is more than the cost of simply locking up a quiet oscillator on the end of a “dirty” cable. I don’t think I’ve ever seen a setup that tries / needs to “distribute” -170 dbc/Hz signals over anything bigger than a rack. I’ve seen *lots* of systems that regenerate those sort of signals many times over (= in many different boxes) to get around distributing them. Bob On Jan 5, 2015, at 2:15 PM, Tom Knox act...@hotmail.com wrote: Happy New Years All! I have seen a number of discussions on various approaches to distribution amps discussed on Time-Nuts ranging from DYI to products intended for Video. I thought I my weigh in with one point of interest; It seems like long term performance is pretty easy, but a low phase noise solution is quite a different story. Looking at the number of application specific products from MicroSemi/Symmetricom and other manufactures claimed and even more so real world specs vary a great deal so apparently it s not easy to just throw something together with great or even good close in phase noise. So depending on your labs direction in the future it may be worth researching and investing in an application specific distribution amp. I like the MicroSemi 4036B but there are a number of very good products out there on the surplus market selling for a small fraction of their original cost. Cheers; Thomas Knox From: bill.ric...@verizon.net To: time-nuts@febo.com Date: Sun, 4 Jan 2015 08:29:34 -0500 Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier? A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm F type with an adapter. Maybe that combination would produce too much garbage. 73, Bill, WA2DVU Cape May --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
On 4 January 2015 at 02:37, Bob Camp kb...@n1k.org wrote: Hi On Jan 3, 2015, at 6:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. I see this http://m.ebay.com/itm/201244302355 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. I actually bought another for $35 which was similar but one of them, the isolation data made no sense, so given their low cost I just bought both. I suspect internally these 16 way units might have a pair of 8 way dividers as there are two isolation figures, depending on what ports one is measuring between Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? the reason for that hassle is to better isolate the outputs. The splitter has good isolation only when all the ports are properly matched. In the case of a “40 db isolation splitter” that can mean the terminations all have 40 db return loss. I bought two of these splitters. One covers 1-30 MHz, the other one 5-200 I think. Anyway, the 1-30 MHz one arrived today, the Minicircuits ZFSC-16-3. I had my VNA on, which unfortunately does not drop down to 10 MHz, or even 30 MHz, as its lower limit is 50 MHz. So I admit these results are a bit shaky, as I'm using the splitter outside its range. But that said, There seems to a reasonable amount of isolation at 50 MHz, even when all other ports are open. At 50 MHz, the loss from the common port is 12.8 dB, and the isolation between two ports sets of ports is either 38 or 48 dB, depending on what ports are chosen. BUT it appears to be improving as one goes lower in frequency. The Minicircuits data sheet makes it clear there are two sets of isolation figures. I'm pretty sure internally this is likely to be a pair of 8-way splitters. When the other splitter is here, I will use another VNA that covers 300 kHz to 9 GHz, and so make some measurements at 10 MHz on both of them. But I just happened to have this VNA calibrated in N, and so done a few quick and dirty measurements. I've made no allowances for losses of cables. So although I admit these measurements are not well done, but I'm not so convinced now that the terminations on the unused ports matters a huge amount. I looks to me that this unit might well exceed 40 dB isolation on all ports at 10 MHz, as all the graphs are sloping in the right direction. Dave common-to-port-7-others-open-S21-magnitude.pdf Description: Adobe PDF document port1-to-port-7-Common=50Ohm-others=open-S21-magnitude.pdf Description: Adobe PDF document port7-to-port-8-Common=50Ohm-others=open-S21-magnitude.pdf Description: Adobe PDF document ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Dave wrote: At 50 MHz, the loss from the common port is 12.8 dB, and the isolation between two ports sets of ports is either 38 or 48 dB To get the worst-case output-to-output isolation, you need to test two output ports that are electrically adjacent (i.e., that share the same last 2:1 splitter, assuming that the 1:16 is a hierarchy of 1:2 splitters -- which is the case with the multi-output splitters I'm familiar with). You may already have found an electrically-adjacent pair (ports 7 and 8), but to be absolutely sure, you would need to repeat the test from one output to each of the 15 others (or find a full internal connection diagram, which does not seem to be on the datasheet). If it is a hierarchy of 1:2 splitters, you are correct that it is effectively two, 1:8 splitters. In that case, each output port on one of the 1:8 splitters is electrically equidistant from all of the output ports on the other 1:8 splitter. But the same is not true of the output ports of just one of the 1:8 splitters. In that case, there is one adjacent output port, two output ports at one remove, and four output ports twice removed. The isolation is generally worst between adjacent outputs, and better at each remove. It is logical to think that the adjacent output ports are 1-2, 3-4, ... 7-8, ... and 15-16 -- but this may not be the case. I wouldn't bother retesting with out-of-band signals, but when you test at 10MHz it is something to think about. Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Just to say, the comment on the graphs that the VNA covers 50 MHz to 20 MHz, is obviously wrong. My 8720D covers 50 MHz to 20 GHz. I do have another couple of VNAs here that cover 10 MHz. I will do some more measurements, with a more suitable VNA when I have both splitters here and some time for something that's not a high priority. I am not yet writing off the possibility of using the power amp and one of these 16-way splitters, as I probably have enough bits in my junk box to do it; and my initial observations are that the isolation doesn't depend too much on the terminations on unused ports. Bob questioned the need for 16 ports. I counted up and I have 9 bits of test kit which take an external reference. So having 16 ports, while nearly double I need now, is not so grossly over the top. Dave ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Bruce wrote: A 10nF cap connected to the emitter winding [instead of the collector] avoids capacitively coupling collector power supply noise to the output (assuming that the collector supply isnt ground.). Good point. I take pains with power supply design and very rarely have problems with supply noise in practice, but you're right, taking the output from the emitter winding should help reduce PS noise coupling if it were a problem. I foresee no countervailing adverse consequences, so that should be considered the preferred connection for the two-winding variant of the circuit. Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Hi Any time you run into terms like “low noise” it pays to think about what that means to you and your system. A quick scan of the posts here over the years will show that different definitions of low noise do exist. The same is true of system requirements. An offset that matters to one may have no impact at all on another system. In some cases -155 dbc/Hz at 10KHz or 100 KHz is “low noise”. In other cases “low noise” is -180 dbc/Hz. In either case, *delivering* a clean signal without spurs and crud is far from simple. In many long cable run cases, the cost of fancy cables, high performance magnetics, and all the other “stuff” is more than the cost of simply locking up a quiet oscillator on the end of a “dirty” cable. I don’t think I’ve ever seen a setup that tries / needs to “distribute” -170 dbc/Hz signals over anything bigger than a rack. I’ve seen *lots* of systems that regenerate those sort of signals many times over (= in many different boxes) to get around distributing them. Bob On Jan 5, 2015, at 2:15 PM, Tom Knox act...@hotmail.com wrote: Happy New Years All! I have seen a number of discussions on various approaches to distribution amps discussed on Time-Nuts ranging from DYI to products intended for Video. I thought I my weigh in with one point of interest; It seems like long term performance is pretty easy, but a low phase noise solution is quite a different story. Looking at the number of application specific products from MicroSemi/Symmetricom and other manufactures claimed and even more so real world specs vary a great deal so apparently it s not easy to just throw something together with great or even good close in phase noise. So depending on your labs direction in the future it may be worth researching and investing in an application specific distribution amp. I like the MicroSemi 4036B but there are a number of very good products out there on the surplus market selling for a small fraction of their original cost. Cheers; Thomas Knox From: bill.ric...@verizon.net To: time-nuts@febo.com Date: Sun, 4 Jan 2015 08:29:34 -0500 Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier? A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm F type with an adapter. Maybe that combination would produce too much garbage. 73, Bill, WA2DVU Cape May --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Happy New Years All! I have seen a number of discussions on various approaches to distribution amps discussed on Time-Nuts ranging from DYI to products intended for Video. I thought I my weigh in with one point of interest; It seems like long term performance is pretty easy, but a low phase noise solution is quite a different story. Looking at the number of application specific products from MicroSemi/Symmetricom and other manufactures claimed and even more so real world specs vary a great deal so apparently it s not easy to just throw something together with great or even good close in phase noise. So depending on your labs direction in the future it may be worth researching and investing in an application specific distribution amp. I like the MicroSemi 4036B but there are a number of very good products out there on the surplus market selling for a small fraction of their original cost. Cheers; Thomas Knox From: bill.ric...@verizon.net To: time-nuts@febo.com Date: Sun, 4 Jan 2015 08:29:34 -0500 Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier? A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm F type with an adapter. Maybe that combination would produce too much garbage. 73, Bill, WA2DVU Cape May --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm F type with an adapter. Maybe that combination would produce too much garbage. 73, Bill, WA2DVU Cape May --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Dave wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. * * * 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? Is 10 dBm an optimal value? I see several distribution amp designs witb one amplifier on each output, but is it just a lot less hassle to split a higher power amp. It all depends on what you need. If the job is feeding the time base inputs of test equipment from a GPSDO, the splitter approach should work fine if you bear a few things in mind. First, the splitter achieves its rated isolation only if it is matched well at the input and *all* outputs. That at least means using dummy loads on unused outputs, but consider that the REF inputs of most instruments are not 50 ohm loads (usually ~ 1k ohm). So, you would need to provide proper termination for the in-use outputs, too. Ideally, it would be in the form of a 52.6 ohm pass-through load at the instrument, so the coax is terminated in 50 ohms at the load (this assumes the instrument has a 1k ohm input -- if not, the pass-through terminator would need to be recalculated -- but note that only 50 and 75 ohm pass-through terminators are likely to be available as commercial items). Second, the amplifier should put out about 25dBm from a 50 ohm source, so each load will receive the standard 1Vrms = 13dBm (10dBm would probably work OK for most instruments, but they usually are fed 13dBm). If the amplifier is not naturally matched to 50 ohms, there will be additional loss in the matching network. Amplifiers that put out 25-35dBm with harmonics below, say, -50dBc are not trivial to design or build. (Not terribly difficult, but not trivial.) I used the splitter topology for the multicoupler that multiplexes antennas to eight receivers. In that case, an amplifier with extremely low noise and high dynamic range, with a natural 50 ohm output -- the sort of amplifier people use these days for post-mixer amps in HDR receivers -- works very well. But the radios are all 50 ohm loads to begin with, so I didn't need to muck about with odd value pass-through terminators. For distributing 10MHz to test equipment, I find it much easier to get good results with a distributed amplifier approach. The circuit I posted back on Nov. 26 is about as simple as it gets, but can be made even simpler. As drawn, each stage uses a 1:1:1 transformer, with the output taken from one of the windings. If the output winding is deleted, the transformer becomes a simple 1:1 and the output is taken through a 10nF blocking capacitor straight from the collector. Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
On Sunday, January 04, 2015 03:39:48 AM Charles Steinmetz wrote: Dave wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. * * * 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? Is 10 dBm an optimal value? I see several distribution amp designs witb one amplifier on each output, but is it just a lot less hassle to split a higher power amp. It all depends on what you need. If the job is feeding the time base inputs of test equipment from a GPSDO, the splitter approach should work fine if you bear a few things in mind. First, the splitter achieves its rated isolation only if it is matched well at the input and *all* outputs. That at least means using dummy loads on unused outputs, but consider that the REF inputs of most instruments are not 50 ohm loads (usually ~ 1k ohm). So, you would need to provide proper termination for the in-use outputs, too. Ideally, it would be in the form of a 52.6 ohm pass-through load at the instrument, so the coax is terminated in 50 ohms at the load (this assumes the instrument has a 1k ohm input -- if not, the pass-through terminator would need to be recalculated -- but note that only 50 and 75 ohm pass-through terminators are likely to be available as commercial items). Second, the amplifier should put out about 25dBm from a 50 ohm source, so each load will receive the standard 1Vrms = 13dBm (10dBm would probably work OK for most instruments, but they usually are fed 13dBm). If the amplifier is not naturally matched to 50 ohms, there will be additional loss in the matching network. Amplifiers that put out 25-35dBm with harmonics below, say, -50dBc are not trivial to design or build. (Not terribly difficult, but not trivial.) I used the splitter topology for the multicoupler that multiplexes antennas to eight receivers. In that case, an amplifier with extremely low noise and high dynamic range, with a natural 50 ohm output -- the sort of amplifier people use these days for post-mixer amps in HDR receivers -- works very well. But the radios are all 50 ohm loads to begin with, so I didn't need to muck about with odd value pass-through terminators. For distributing 10MHz to test equipment, I find it much easier to get good results with a distributed amplifier approach. The circuit I posted back on Nov. 26 is about as simple as it gets, but can be made even simpler. As drawn, each stage uses a 1:1:1 transformer, with the output taken from one of the windings. If the output winding is deleted, the transformer becomes a simple 1:1 and the output is taken through a 10nF blocking capacitor straight from the collector. A 10nF cap connected to the emitter winding avoids capacitively coupling collector power supply noise to the output (assuming that the collector supply isnt ground.). Bruce Best regards, Charles ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Hi On Jan 3, 2015, at 10:37 PM, paul swed paulsw...@gmail.com wrote: Dave I am sure there will be many answers. But yes indeed it will work fine. All of the outputs should have the same delay also and that may be useful. There really are the two approaches. The big power amp thats a 1/2 Watt you are talking and the many small amps as in the distributed mode. Whats interesting is the telcos always do the big amp splitter and the test equipment manufactures use precision distributed distribution amps. I guess its a pick your poison. Or maybe the test equipment manufacturers needed more isolation port to port. Or heavens maybe they could just sell them for more money. Would they do that? The telco types were used to the need to terminate all the lines correctly. It’s been part of their DNA for 100 years. They also are used to designing cable plants rather than just tossing wires around. They also have some needs like 20 year MTBF, so orderly is a good idea. If I see a properly terminated single drop standard line in a real working lab, it will be the first time I see one. BNC Tee’s seem to be a popular item when hooking up instruments in a typical lab. (Note - in this case the definition of “properly terminated” is 40 db return loss, so it’s as good as the splitter). More or less - the instrument guys opted for a “tap off multiple instruments” approach. The telco guys opted for a “individual run to each instrument” approach. Did every single outfit all over the world read the exact same book? Certainly not, the real world is never that orderly. Telco’s are not 100% fixed, labs are not 100% random wired. So what happens: Telco has a problem, it’s a fixed plant. They track it down and do what’s needed. The problem (hopefully) does not come back. Lab has a problem, It’s Bob over on the third bench from the end. They try to track it, Bob moves on in his troubleshooting. They never find it. Much oratory, very little labor. How often does that happen? Roughly three of four times a week where I work… We find it and fix it about half the time. The rest of the time it “just goes away” or people get tired of looking. Most common issue - can’t run a clean phase noise / ADEV / vibe plot with that silly gizmo running on (name deleted to protect Bob)’s bench. Less common issues - can’t get a clean counter reading on standard line #XXX. So yes, a real lab does go for more isolation and better protection that a telco. Undiagnosed / random problems from shorts and opens are very real in the lab, not so much in the telco. 10 MHz threat signals and 10 MHz standards are common in the lab, less so in the telco. Different systems, different needs, different solutions. At least in my basement, I’m a lot closer to a lab than a telco. I move stuff around, I turn gear on and off. I set things up and tear them down. I do indeed work on a lot of stuff that runs at 10 MHz. I have multiple 10 MHz sources running all the time. Troubleshooting every cable connection for issues is not much fun. Isolation does indeed matter in a situation like that. Even with all my junk, I don’t have a *need* for a 16 output system. I doubt I ever have more than a dozen taps running on my Spectracom at any one time. 16 boxes is a *lot* of stuff. Are there some exotic situations that come up - sure. What’s exotic to me might be normal to you. My typical might be your exotic. Do close in spurs matter to you? They do to me. Does a “burp” (phase shift) in all the standards when a cable is unplugged matter to you? It does to me. Do you run stuff 24/7 365 days a year? I do sometimes (yes yell at me for “sometimes and 365”). Do you need -175 dbc/Hz phase noise on your standard lines? I don’t. Do you need a range of standard frequencies (100K, 1M, 5M, 10M)? I do. Do you have some stuff (= almost everything) that’s fine at 1x10^-11 at 1 second wired one way and other stuff wired another? I do. How much do you listen to WWV at 5 or 10 MHz? Me - not so much. Again, different needs, will drive different solutions. Bob Humor aside each has a very good reason for doing the distribution and its driven by the requirements. I have several of those spitters and picked them up for $ 0 at hamfests. Seems no one had a use for them when all of the 900 Mhz gear came out of the sites. Mostly gone at this point. A 1/2 watt 10 Mhz amp is not that hard to build look at the many Ham sites we have a band close to 10 Mhz/ 30 Meter. Regards Paul WB8TSL On Sat, Jan 3, 2015 at 6:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. I see this http://m.ebay.com/itm/201244302355 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. I actually bought another for $35 which was similar but one of them, the
Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier?
Friends in Time, There's been a large amount of discussion about distribution amps on this list. People may be using them just because that's what's done. So I ask you: What are we trying to isolate? The destination devices do not generate an interfering signal, n'est ce pas? The receiving devices do not need to have 50 ohms input impedance if the source cable is properly terminated, no? If I use high impedance receivers tapped off a terminated line, how is this different from 10 base T? Yes, there will be cable delay between receivers, but how were you going to avoid that with your distribution amp? Put another way, why do counters like the Racal 1992 allow you to choose 50 ohm or high impedance at the input? Please, no take it on faith audiophile answers. HNY. Bill Hawkins ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Almost all frequency counters have an internal source which is a potential means of injection locking an external reference if the isolation between the internal source and the external source is inadequate. High impedance taps on a single terminated line ensure that the isolation between such internal sources and the shared line is limited by the isolation afforded by the internal source selection gating/switching of each device.adding or removing a tap invariably changes the phase shift between the source and each of the other receivers.The minimum isolation required can be estimated from the maximum acceptable frequency shift, the resonator Q and internal reverse isolation between the source output and the resonator Q. Frequency distribution systems like the Spectracom 8140 with wide range ADC tend to degrade the source phase noise significantly with respect to non agc distribution systems. Bruce On Sunday, 4 January 2015 9:41 PM, Bill Hawkins b...@iaxs.net wrote: Friends in Time, There's been a large amount of discussion about distribution amps on this list. People may be using them just because that's what's done. So I ask you: What are we trying to isolate? The destination devices do not generate an interfering signal, n'est ce pas? The receiving devices do not need to have 50 ohms input impedance if the source cable is properly terminated, no? If I use high impedance receivers tapped off a terminated line, how is this different from 10 base T? Yes, there will be cable delay between receivers, but how were you going to avoid that with your distribution amp? Put another way, why do counters like the Racal 1992 allow you to choose 50 ohm or high impedance at the input? Please, no take it on faith audiophile answers. HNY. Bill Hawkins ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Hi On Jan 3, 2015, at 6:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. I see this http://m.ebay.com/itm/201244302355 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. I actually bought another for $35 which was similar but one of them, the isolation data made no sense, so given their low cost I just bought both. I suspect internally these 16 way units might have a pair of 8 way dividers as there are two isolation figures, depending on what ports one is measuring between Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? Is 10 dBm an optimal value? no, 13 to 15 is better. I see several distribution amp designs witb one amplifier on each output, but is it just a lot less hassle to split a higher power amp the reason for that hassle is to better isolate the outputs. The splitter has good isolation only when all the ports are properly matched. In the case of a “40 db isolation splitter” that can mean the terminations all have 40 db return loss. I have a range of Minicircuits amps in my junk box in little enclosures, which means a distribution amp can be built from just 3 main components Roughly 99.9% of all those little amps degrade the phase noise of the input signal significantly when driven near their “rated” output power. If you are after 13 dbm after 12 db loss you need 25 dbm clean signal. If you need to run the amp 10 db below it’s rated output to keep it clean, that means an amp rated at 35 dbm output. Most of those amps are 10% efficient, so you will be putting 20W into the device. The next layer is the return loss on the output of the amp. If you are after the full isolation numbers it needs to be matched as well as the terminations. If you need a pad to achieve that match, it comes out of your power budget. * PSU * Power amplifier * 16 way splitter. That seems a *lot* simpler than many designs I see. Since your test gear typically does *not* provide a 50 ohm match (they are high Z inputs), making this sort of setup work is fairly complex. You need to terminate at each device and terminate each unused output on the splitter. Even then I was looking to feed it with an HP 58503A or similar device. I do have an amplifier in my junk box which will produce 27 dBm. If I combined that with 16 x 5 dB attenuators I could improve the isolation by 10 dB, but I am unlikely to find the attenuators cheaply, and buying new would add at least $200-$300 to the price, for what I suspect is no significant benefit. For under $20 in active parts you can build a distribution box that will do a far better job than a big amp driving a multi port splitter. Bob Dave ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
Dave I am sure there will be many answers. But yes indeed it will work fine. All of the outputs should have the same delay also and that may be useful. There really are the two approaches. The big power amp thats a 1/2 Watt you are talking and the many small amps as in the distributed mode. Whats interesting is the telcos always do the big amp splitter and the test equipment manufactures use precision distributed distribution amps. I guess its a pick your poison. Or maybe the test equipment manufacturers needed more isolation port to port. Or heavens maybe they could just sell them for more money. Would they do that? Humor aside each has a very good reason for doing the distribution and its driven by the requirements. I have several of those spitters and picked them up for $ 0 at hamfests. Seems no one had a use for them when all of the 900 Mhz gear came out of the sites. Mostly gone at this point. A 1/2 watt 10 Mhz amp is not that hard to build look at the many Ham sites we have a band close to 10 Mhz/ 30 Meter. Regards Paul WB8TSL On Sat, Jan 3, 2015 at 6:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. I see this http://m.ebay.com/itm/201244302355 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. I actually bought another for $35 which was similar but one of them, the isolation data made no sense, so given their low cost I just bought both. I suspect internally these 16 way units might have a pair of 8 way dividers as there are two isolation figures, depending on what ports one is measuring between Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? Is 10 dBm an optimal value? I see several distribution amp designs witb one amplifier on each output, but is it just a lot less hassle to split a higher power amp. I have a range of Minicircuits amps in my junk box in little enclosures, which means a distribution amp can be built from just 3 main components * PSU * Power amplifier * 16 way splitter. That seems a *lot* simpler than many designs I see. I was looking to feed it with an HP 58503A or similar device. I do have an amplifier in my junk box which will produce 27 dBm. If I combined that with 16 x 5 dB attenuators I could improve the isolation by 10 dB, but I am unlikely to find the attenuators cheaply, and buying new would add at least $200-$300 to the price, for what I suspect is no significant benefit. Dave ___ 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] Any reason not to use one power amplifier and splitter for distribution amplifier?
My 2 cents. I just repurposed an RGB video distribution amp for use with a rubidium. The board has three EL2070 (200 MHz BW) amps, each one feeds several BNC jacks for RGB output. I only need three separate, isolated outputs, so I am feeding the rubidium into all three EL2070's and only taking one output from each chip, via an isolation transformer. This seems to be working just fine for my intended purpose. I still need to add the DDS and a few other items to the box to complete the project. Joe Gray W5JG On Sat, Jan 3, 2015 at 8:37 PM, paul swed paulsw...@gmail.com wrote: Dave I am sure there will be many answers. But yes indeed it will work fine. All of the outputs should have the same delay also and that may be useful. There really are the two approaches. The big power amp thats a 1/2 Watt you are talking and the many small amps as in the distributed mode. Whats interesting is the telcos always do the big amp splitter and the test equipment manufactures use precision distributed distribution amps. I guess its a pick your poison. Or maybe the test equipment manufacturers needed more isolation port to port. Or heavens maybe they could just sell them for more money. Would they do that? Humor aside each has a very good reason for doing the distribution and its driven by the requirements. I have several of those spitters and picked them up for $ 0 at hamfests. Seems no one had a use for them when all of the 900 Mhz gear came out of the sites. Mostly gone at this point. A 1/2 watt 10 Mhz amp is not that hard to build look at the many Ham sites we have a band close to 10 Mhz/ 30 Meter. Regards Paul WB8TSL On Sat, Jan 3, 2015 at 6:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I was looking to make a 10 MHz distribution amp to feed test equipment with the output of a GPSDO. I see this http://m.ebay.com/itm/201244302355 16-way Minicircuits splitter on eBay which I got for $40. I guess the loss is around 12 dB. I actually bought another for $35 which was similar but one of them, the isolation data made no sense, so given their low cost I just bought both. I suspect internally these 16 way units might have a pair of 8 way dividers as there are two isolation figures, depending on what ports one is measuring between Is there any reason not to just drive that with 22 dBm or so of power to get 10 dBm at each of 16 ports? Is 10 dBm an optimal value? I see several distribution amp designs witb one amplifier on each output, but is it just a lot less hassle to split a higher power amp. I have a range of Minicircuits amps in my junk box in little enclosures, which means a distribution amp can be built from just 3 main components * PSU * Power amplifier * 16 way splitter. That seems a *lot* simpler than many designs I see. I was looking to feed it with an HP 58503A or similar device. I do have an amplifier in my junk box which will produce 27 dBm. If I combined that with 16 x 5 dB attenuators I could improve the isolation by 10 dB, but I am unlikely to find the attenuators cheaply, and buying new would add at least $200-$300 to the price, for what I suspect is no significant benefit. Dave ___ 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.
