Re: [time-nuts] thoughts on lightning arrestors
Lightening arresters don't have to handle that much energy. When a strike hits a mast with an antenna on it the current divides. Most of it should go straight down the tower or mast into the ground. This is why the structure is bonded to a grounding system using a straight line path with ground rods directly under the tower Some of the current finds it's way to the coaxial shield and flows to ground at he bulkhead coupler that is also grounded. Some fraction actually goes into the center conductor of the antenna lead. This is what the lightening arrester has to clamp and shunt to ground. It is a very small part of the total energy from the strike. The tree exploded because it contained water that was heated to vapor very quickly by he current. If the tree had a ground wire from top to bottom the strike would have been uneventful. On Thu, Nov 27, 2014 at 10:40 PM, Mark Sims hol...@hotmail.com wrote: Bark effect? ;-) Lightning hit a tree behind where I lived and three other trees near it also exploded... you ain't gonna arrest a direct lightning strike. -- Chris Albertson Redondo Beach, California ___ 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] Minicircuits 10% discount in December
you can try the following vendor (RF Elettronica): http://www.rf-microwave.com/en/shop.html They ship abroad and prices are rather good. _ Elio. ___ 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] Homebrew frequency counter, need help
I did a little calculation and it's a 10 digits counter. log(10,000,000,005) = 10. There is still a big gap between this one and 53132A :( For 53132A, the time resolution is 150ps, which I think is 10digits/s with interpolator. According to the schematics the only difference between 53132A 53131A is the ADC of interpolator. It is the reason why 53131A only has time resolution of 500ps (also 10digits/s). However, 53132A is a 12 digits/s counter. I guess the 2 more digits come from software. Linear regression maybe ? 2014-11-28 11:15 GMT+08:00 Bob Camp kb...@n1k.org: Hi One way of looking at resolution is at the one standard deviation point. Another way of looking at it is as a +/- 1 digit accuracy point. Each approach has it’s advantages. It’s more common to see single shot timing specified as one sigma and frequency specified as +/- 1 count. Often you need to read the fine print to see just what is being spec’d. On Nov 27, 2014, at 5:30 PM, LiAng lll...@gmail.com wrote: Thanks for the info. What's the standard to be 11 digits/s? For real 11 digits/s, the ADEV needs to reach the 1e-11 level? I'm not sure if my GPSDO Rb is stable enough. Maybe 2 MV89A as the refclk and signal? For the “easy” approach, first feed the counter’s reference back into the input. That will usually give you a “best result no matter what” sort of reading. It also will suppress a variety of problems coming from the reference signal. A source with a 1x10^-12 ADEV at 1 second should be good enough for testing a 10 to 11 digit counter. It’s not going to do the trick for a 12 digit device. In the case of a 12 digit device, use a second copy of what ever you are using for the reference for the counter …. —— Another approach, don’t measure frequency, measure period / time / phase. Generating a pulse that is 100 ns wide is fairly easy. Doing so with 1 ps jitter is not impossible. If your signal source is good to a few ppm, your pulse generation accuracy will be “plenty good enough”. Things like rise and fall times through buffers will be a much bigger deal in the delivered result than the absolute accuracy of the clock feeding the circuit. If the counter measures the resulting pulse with a 10 ps one sigma error, you have a 10 ps counter. If it says that 100 ns is 102 ns, that’s to be expected with a simple pulse generation technique. Yes, you eventually do need to verify that 100 ns is 100 ns, but that can be done a different way. Bob TDC-GP22 has it problem, I will post some data/schematic/source code about it later. Thanks ___ 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] eBay seller has Z3801A upgraded to 58503A
Hi Actually there *is* a reason for all the posts. This stuff comes onto the market very rarely. It *is* legitimate Time Nut gear. While it’s here at a low price it’s worth letting people know about it. The Z3801’s were a cheap item once upon a time (like $150 or so). The TBolt’s were sub $70 items for months on end. We can rightly (and very much should) debate the relative merits of each of these boxes. That’s what the list is for. Another valid use of the list is to let people know when stuff comes available. If you go back through the archives, one of the (many) recurring themes is “if I’d only known what those were back then I’d have bought one at that price”. Part of that process is talking about how to set them up and get them working. The guy will run out of these soon and you can look forward to not hearing about them anymore …. Bob On Nov 27, 2014, at 11:23 PM, Said Jackson saidj...@aol.com wrote: Plus the Z3801A seems to just work. On the Lucent boxes we had to suffer through many 100's of posts over the last month... Sent From iPhone On Nov 27, 2014, at 16:57, Bob Camp kb...@n1k.org wrote: Hi Phase noise at 100 Hz, I’ll give you that on to the Z3801. ADEV on the sample I have of the 3801 and KS boxes are pretty darn close. Bob On Nov 27, 2014, at 6:45 PM, Said Jackson via time-nuts time-nuts@febo.com wrote: The 58503A we got have much better ADEV and PN than what was posted recently on the Lucent boxes. TVB has many plots of the Z3801A on his website - same box. They used to be $399 on eBay, now likely $500 or more, but you get what you pay for.. Sent From iPhone On Nov 27, 2014, at 16:14, Bob Camp kb...@n1k.org wrote: Hi Let’s say that an OCXO based new part is $500. Who knows if that applies to the Furry. If it does, that’s a really good price. Anything below that and Santa Claus is coming to your house early. Are you putting this in a commercial system? Do you expect to need warranty support? I’d bet the reasonable answer to both is no. The KS boxes are $150 for the pair. They are new old stock. Do you believe the newer part works better than the KS ADEV wise? Again I’d say the reasonable answer is no. The KS boxes are essentially the same as a Z3801 in terms of ADEV. You can get (in this example case) three of the KS box pairs and still save money over the new part. Shipping might tip that one way or the other. Why would this matter? With three boxes, you can check them against each other and rule in / rule out problems with any one pair. That’s keeping everything plug and play. If you want to do a few “wire a connector” mods, you can have six sources to compare against each other. You can also have a whole bunch of spares …. Bob On Nov 27, 2014, at 5:58 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: Dr David Kirkby On 27 Nov 2014 23:27, Brooke Clarke bro...@pacific.net wrote: Hi Dave: http://www.ebay.com/itm/171504585820 http://www.prc68.com/I/LTE-LiteGPSDO.html Brooke Clarke I was aware of them, and are still contemplating getting one, but the Fury from Jackson Labs uses an OCXO, so will have better performance. I don't know what that costs though. Clearly more than the LTE Lite. Siad should consider putting the Fury on eBay, but I would rather pay direct, which would save them the eBay fees, so hopefully cost me less. 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. ___ 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] Truetime GPS-DC-416 specs ?
Tim I have nothing. But if it seems operational given the time frame it was built you may run into the gud ole rollover issue. This can usually be gotten around by setting the date and time to a 1024 week from whatever the GPS week is today. There are calculators online. But I suspect if it powers up the real trick is how do you even tell it to do that. Pretty sure it would be an rs232 interface and 9600 8n1. But thats aguess from other truetime products. Good luck. Paul WB8TSL On Thu, Nov 27, 2014 at 10:44 PM, Tim t...@skybase.net wrote: Hi all, Googling around I cant find much info on the Truetime GPS-DC-416 Does anyone have information or specification on that particular model ? thanks Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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] Homebrew frequency counter, need help
Hi On Nov 28, 2014, at 6:26 AM, Li Ang lll...@gmail.com wrote: I did a little calculation and it's a 10 digits counter. log(10,000,000,005) = 10. There is still a big gap between this one and 53132A :( Not if you can hit the advertised time resolution of your chip. Keep on working on this. For 53132A, the time resolution is 150ps, which I think is 10digits/s with interpolator. According to the schematics the only difference between 53132A 53131A is the ADC of interpolator. It is the reason why 53131A only has time resolution of 500ps (also 10digits/s). However, 53132A is a 12 digits/s counter. I guess the 2 more digits come from software. Linear regression maybe ? More like confusing spec’s on the two counters. The timing resolution is what you want to look at in this case. They do some math on multiple internal readings to (hopefully) improve the frequency resolution. Sometimes that magic works, often on real signals it does not make much difference. Bob 2014-11-28 11:15 GMT+08:00 Bob Camp kb...@n1k.org: Hi One way of looking at resolution is at the one standard deviation point. Another way of looking at it is as a +/- 1 digit accuracy point. Each approach has it’s advantages. It’s more common to see single shot timing specified as one sigma and frequency specified as +/- 1 count. Often you need to read the fine print to see just what is being spec’d. On Nov 27, 2014, at 5:30 PM, LiAng lll...@gmail.com wrote: Thanks for the info. What's the standard to be 11 digits/s? For real 11 digits/s, the ADEV needs to reach the 1e-11 level? I'm not sure if my GPSDO Rb is stable enough. Maybe 2 MV89A as the refclk and signal? For the “easy” approach, first feed the counter’s reference back into the input. That will usually give you a “best result no matter what” sort of reading. It also will suppress a variety of problems coming from the reference signal. A source with a 1x10^-12 ADEV at 1 second should be good enough for testing a 10 to 11 digit counter. It’s not going to do the trick for a 12 digit device. In the case of a 12 digit device, use a second copy of what ever you are using for the reference for the counter …. —— Another approach, don’t measure frequency, measure period / time / phase. Generating a pulse that is 100 ns wide is fairly easy. Doing so with 1 ps jitter is not impossible. If your signal source is good to a few ppm, your pulse generation accuracy will be “plenty good enough”. Things like rise and fall times through buffers will be a much bigger deal in the delivered result than the absolute accuracy of the clock feeding the circuit. If the counter measures the resulting pulse with a 10 ps one sigma error, you have a 10 ps counter. If it says that 100 ns is 102 ns, that’s to be expected with a simple pulse generation technique. Yes, you eventually do need to verify that 100 ns is 100 ns, but that can be done a different way. Bob TDC-GP22 has it problem, I will post some data/schematic/source code about it later. Thanks ___ 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] Homebrew frequency counter, need help
Hi On Nov 28, 2014, at 7:04 AM, Li Ang lll...@gmail.com wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). Which is a very good reason to play with it … TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. This may be the resolution / accuracy thing I mentioned above. Don’t give up quite yet though. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Gee … that sounds like the documentation on a LOT of parts these days…. It’s also what keeps people from trying this sort of thing. A few hardware questions: 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) 2) Is there more bypassing on the circuit than shown? (If not, add some more). 3) How confident are you of your input signal? (can you check it with a “known good” counter?) 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things …) A full counter will have a bit more “stuff” than just this chip. I think getting this part working *before* you work on the rest of it is a very good idea. One small piece at a time …. Bob Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. tdc_gp22.GIF___ 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] Truetime GPS-DC-416 specs ?
Hi One quick thing to check (I have never seen one of these): Some of the early boxes used downconverters at the antenna end rather than just a preamp at the antenna. On a few boxes the giveaway was two coax ports headed to the downconverter. On most everything was multiplexed on one cable. If you need a downconverter and it did not come with the box, they are pretty tough to find. I have several boxes sitting around lacking downconverters to make them work. Another thing it might have is an odd preamp voltage to the antenna. That’s a lot easier to get around than the downconverter. A DC block and bias tee will do the trick. Just don’t plug a 5V antenna into it before you check to see if it’s got something like 12V on the coax ... Bob On Nov 28, 2014, at 8:31 AM, paul swed paulsw...@gmail.com wrote: Tim I have nothing. But if it seems operational given the time frame it was built you may run into the gud ole rollover issue. This can usually be gotten around by setting the date and time to a 1024 week from whatever the GPS week is today. There are calculators online. But I suspect if it powers up the real trick is how do you even tell it to do that. Pretty sure it would be an rs232 interface and 9600 8n1. But thats aguess from other truetime products. Good luck. Paul WB8TSL On Thu, Nov 27, 2014 at 10:44 PM, Tim t...@skybase.net wrote: Hi all, Googling around I cant find much info on the Truetime GPS-DC-416 Does anyone have information or specification on that particular model ? thanks Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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] Homebrew frequency counter, need help
1) What frequency is the crystal at? (can you drive the chip from an OCXO?) I'm clking this chip with the refclk/2=5Mhz, which is done by cpld. something like always @(posedge refclk) tdc_clk = ~tdc_clk; Not sure if it's noisy. 2) Is there more bypassing on the circuit than shown? (If not, add some more). Since there is only few power supply pins, I just put 100uF + 100nF there. I can try put more to see if helps. And I'm going to use dedicated LDO for digital part and analog part next time to make a new pcb. 3) How confident are you of your input signal? (can you check it with a “known good” counter?) The best counter I get is the RACAL DANA 1992. That is not good enough. I think the accurarcy is not a problem, as if the reference is good enough, it's only the matter of math. I prefer to enhance the resolution and reduce noise. I'm using Trimble GPSDO(NTPX26AB) as the signal source and FE5650 Rb as the ref. I've tried Rb+MV89A and Rb + SMY01 signal generator, same performance. The 2nd-hand 53132A,PM6690,SR620 about 600~800$ here in China. I'm trying not to get one unless necessary. If I have get one to compare the performance, what's your suggested model? 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things …) I'll try to remove that tomorrow All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. I guess the accuracy is not important in the interpolator scenario. It has a feature to output the result of delta_time / ref_cycle_time(it will measure the 2cycle_time - 1cycle_time after the delta_time measurement and do the float calculation). All I need is this part(it's the fraction part of refcnt). So if I can reach 90ps resolution they claim, the counter can tell 1/1000 of one reference cycle. That's 3 digits. Thanks. ___ 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] Homebrew frequency counter, need help
Hi On Nov 28, 2014, at 10:14 AM, Li Ang lll...@gmail.com wrote: 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) I'm clking this chip with the refclk/2=5Mhz, which is done by cpld. something like always @(posedge refclk) tdc_clk = ~tdc_clk; Not sure if it's noisy. If the clock source into the CPLD is clean, the output should not be to bad. 2) Is there more bypassing on the circuit than shown? (If not, add some more). Since there is only few power supply pins, I just put 100uF + 100nF there. I can try put more to see if helps. And I'm going to use dedicated LDO for digital part and analog part next time to make a new pcb. I suspect that a few more 100nF caps might be a good idea. They may not help, but it would rule out the supply as an issue. 3) How confident are you of your input signal? (can you check it with a “known good” counter?) The best counter I get is the RACAL DANA 1992. That is not good enough. I think the accurarcy is not a problem, as if the reference is good enough, That’s correct. I was hoping you might be able to borrow a SR620 or 53132 for a few minutes to check your input signal. it's only the matter of math. I prefer to enhance the resolution and reduce noise. If the noise is on your test signal, it can be very frustrating to chase it with a lot of software work. I'm using Trimble GPSDO(NTPX26AB) as the signal source The GPSDO should be fairly quiet, but it has an ADEV that’s a bit high. The outputs also can have noise on them. and FE5650 Rb The FE Rb’s tend to have a lot of spurs on the output. In some cases that can get you in trouble. as the ref. I've tried Rb+MV89A If the MV89A is working properly, it should be a pretty good source. Based on some of the prices I’ve seen on the internal China market, you might get a couple of them as sources. and Rb + SMY01 signal generator, same performance. The 2nd-hand 53132A,PM6690,SR620 about 600~800$ here in China. I'm trying not to get one unless necessary. If I have get one to compare the performance, what's your suggested model? The SR620 is a good counter, so is the 53132. They both can have problems. The 53132 display wears out and it’s power supply can fail. The 620 can run a bit hot, which kills a variety of parts in it. It’s better to pay a bit more for one you can actually check out before you buy than to get one shipped in. 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things …) I'll try to remove that tomorrow It may be allowing the supply to drop a bit when the chip goes into some sort of computation. Often these things happen at just the wrong time … If you have a CPLD and a MV89: 1) With a 10 MHz sine wave out of the OCXO, you need to convert it to logic first. A biased input is a pretty good way to do this. 2) Generate 200 or 400 ns wide pulses out of the CPLD for testing. That will eliminate any issues from the 5 MHz crystal in the MV-89. 3) Keep the PCB as simple as you can. You need at least a double sided board (one side ground plane). If you can get a cheap 4 layer board, go for it. A full internal ground plane is a good thing. 4) Route the high speed signals (like the OCXO output) through solid connections. Flying wire leads are not a good idea. Mounting a MV89 direct to the PCB is a good way to do things. SMA connectors are also good. 5) If you have an oscilloscope or can borrow one, take a look at the signals on your board. Even a quick check can tell you a lot about signals that are not what they should be. 6) Be careful of ground loops and power supply issues. I’ve spent a *lot* of time on breadboards that didn’t work because I had power line noise running around. Good luck !! Bob All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. I guess the accuracy is not important in the interpolator scenario. It has a feature to output the result of delta_time / ref_cycle_time(it will measure the 2cycle_time - 1cycle_time after the delta_time measurement and do the float calculation). All I need is this part(it's the fraction part of refcnt). So if I can reach 90ps resolution they claim, the counter can tell 1/1000 of one reference cycle. That's 3 digits. Thanks. ___ 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] thoughts on lightning arrestors
Hi Any form of protection (no matter what you are protecting against) is part of a system. The more complex the system, the more it costs and the larger it gets. The more details you cover in your system the more 9’s you get to put in the “99.9xxx% protection” statement. Is there an event out there that will be the 0.001% event - sure. Are we talking about lightning or redundant timing systems? - it really does not matter. The same principle applies to both. Are two GPSDO’s enough? Would adding a couple of Cs standards make it better? You are just adding more 9’s to the number. Put a structure over your house that looks like the one over your local power switching station and you add a few more 9’s on the lightning protection number. Same idea as adding a few Cs standards to your system. In both examples, the added gear will only add 9’s if it’s part of a properly designed system. Simply adding more of isn’t likely to help much compared to a careful design. People make timing setups that run pretty much forever and ever. A mountain top (or skyscraper top) communications setup can be designed to take multiple direct lightning hits an hour and keep right on going and do it for may years. There are *lots* of systems out there like that. All of it just takes a careful approach with good attention to the details. Yes there is the minor issue of having enough cash on hand to pay for what’s required ... Bob On Nov 28, 2014, at 11:26 AM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Nov 27, 2014 at 9:12 PM, Bill Hawkins b...@iaxs.net wrote So I wonder about this concept of a lightning arrestor. The report referenced by Arthur Dent is quite complete. It also says, at the bottom of page two, It is impossible to prevent damage from a direct lightning strike ... Why, then, do people sell lightning arrestors when they wouldn't dream of selling hurricane arrestors? Because the lightening arresters actually work. That is why they are sold and wide used. They do not and can not stop lightening. What they do is act as a switch. They sense the voltage on a conductor. Normally the conductor is allowed to have a signal voltage on it but if the voltage relative to ground goes high the arrester closes a switch and connects the conductor to ground. They don't stop lightening, they simply close to provide a path to ground. The tree could have been protected too. Let's say we could measure the voltage at the top of the tree and if it ever got high we'd connect the top of the tree to ground via a study copy cable. Then the current would have avoided the tree trunk and flowed harmlessly to ground. What is amazing is that we can build a simple switch that can work so fast. Many of them work by using some kind of gas that is non-conductive until it becomes ionized then the ionized gas connects the conductor to ground. Also the arrester never sees the full current of the strike. In a coaxial antenna cable MOST of the current is on the shield and this is shunted to ground directly and never goes into the arrester. And BTW we do build and use hurricane arrestors. They are called storm shelters. A large concrete structure works pretty much like a lightening arrester, it deflects the effects of the storm from some small protected area. We should not argue that lightening protection is impossible because we have many thousand of examples of them working. Yes normal variations and statistics will eventually take out a system. But will it happen in your lifetime? OK one more analogy. Earthquakes. Why bother with robust building codes when we know that a big enough quake will destroy any building? It's because the big one is unlikely to occur during the building's lifetime but we know 100% that many smaller ones will occur. So we protect for the normal case These things obviously DO WORK. There are cell towers all over the Orlando Florida and they continue to operate. With a cell tower the FIRST line of defense is structural grounding. The steel structure is bonded to a copper grounding system. They get this down to about 6 ohms tower to ground and most of the current follows that path. The second line is surge protectors on ALL wires that come into the building. Again you do NOT stop lightening with an arrester, you use them to provide a easy path to ground.. -- Chris Albertson Redondo Beach, California ___ 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] Distribution Amp
Any of the group using the TADD-1 from TAPR. Perhaps that unit along with double shielded cables would work for most folks. Looking at the past threads are we trying to reinvent the wheel for a distribution solution? 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] Minicircuits 10% discount in December
Rick, Thanks for the brief review of MiniCircuits stuff (I'm not connected with them in any way except as a customer). Since you've characterized some of their parts, perhaps you could help answer a question that someone else posted, and one that I would like to have answered as well. Have you measured the effects of DC current in the windings of an RF transformer, such as is seen if the transformer is in the collector circuit of an amplifier? If so, could you provide a generalization of the effects, such as changes in frequency response, losses, etc.? Many Thanks!, Dave M Richard (Rick) Karlquist wrote: On 11/27/2014 7:07 AM, Tim Shoppa wrote: For a hobbyist doing things a few at a time, what advantage is there to buying RF transformers made by Mini-circuits etc., vs winding them using commonly available ferrite cores/binocular cores? If I needed to do a production run of 1000+ boards with tiny SMT transformers, sure, no problem buying them from mini-circuits or a distributor etc. But for hobbyist stuff seems far more flexible to wind them onesy-twosy using not so tiny cores and windings selected for the particular application. Tim N3QE You need the tiny cores to get the performance of the MiniCircuits transformers. You just can't get the same bandwidth using macro sized binocular cores. Now, if you don't need a lot of bandwidth, then what you are saying could make sense. Another issue is stray capacitance. Considerably lower with a tiny core. I have spent many hours characterizing MiniCircuits transformers beyond the data sheet specs, and dissecting them to learn how they do it. They really do have a lot of rocket science in them. In terms of the engineering I am buying (especially in a one-off application) they are ridiculously cheap. And I say that as a fairly knowledgeable transformer designer in my own right. I do keep binocular cores around for higher power transformers, and for emergencies when I need a transformer yesterday. Rick Karlquist N6RK ___ 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] Distribution Amp
Bill, there are lots of us here that are well aware of the TAPR products, and recognize their merits. There are also lots of us here that like to roll our own (me included). Many of us aren't engineers or engineering students, but we still like to participate in the technology. A little help, in the form of a schematic or a detailed construction project, is always welcome, even if there is an available product for sale. Not reinventing the wheel, just that some of us like to do the mounting and balancing ourselves. Dave M billriches wrote: Any of the group using the TADD-1 from TAPR. Perhaps that unit along with double shielded cables would work for most folks. Looking at the past threads are we trying to reinvent the wheel for a distribution solution? 73, Bill, WA2DVU Cape May ___ 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] Distribution Amp
Hi Dave, Speaking only for myself, most of the fun is in the reinventing of the wheel. I have no real use for a frequency standard, but designing and building my GPSDO has been very rewarding. Eventually I hope to be able to share it with someone besides Dan, who has been a big help on the hardware side. A lot of the fun has been in comparing the results to my 10811 and my new KS-24361. Then there's the thermal stability question and on and on. As to distribution amps, I have to defer to the engineers on the group. I believe Bob Camp has posted about the need to compare what the end use is going to be vs the quality of what we're feeding to the DA. Those who need a high quality DA will mostly likely buy one. Those like me will likely try to measure what we have and see if we can improve it somehow. Otherwise, I'm spending my retirement watching TV. Where's the fun in that? =) Hopefully this forum has room for professionals, amateurs, and dilettantes like me. Bob - AE6RV From: Dave M dgmin...@mediacombb.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, November 28, 2014 12:23 PM Subject: Re: [time-nuts] Distribution Amp Bill, there are lots of us here that are well aware of the TAPR products, and recognize their merits. There are also lots of us here that like to roll our own (me included). Many of us aren't engineers or engineering students, but we still like to participate in the technology. A little help, in the form of a schematic or a detailed construction project, is always welcome, even if there is an available product for sale. Not reinventing the wheel, just that some of us like to do the mounting and balancing ourselves. Dave M billriches wrote: Any of the group using the TADD-1 from TAPR. Perhaps that unit along with double shielded cables would work for most folks. Looking at the past threads are we trying to reinvent the wheel for a distribution solution? 73, Bill, WA2DVU Cape May ___ 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] Distribution Amp
On Fri, Nov 28, 2014 at 10:23 AM, Dave M dgmin...@mediacombb.net wrote: A little help, in the form of a schematic or a detailed construction project, is always welcome, Then look at the TAPR user manual. Schematic and layout are in the manual. You can modify it to suit your needs. I think one of the pampas is not longer in production but you can use a search on the Digikey web site to find a replacement . I think this is what people meant, not to simply buy the TAPR product but to study its design. -- Chris Albertson Redondo Beach, California ___ 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] Minicircuits 10% discount in December
On 11/28/2014 10:08 AM, Dave M wrote: Rick, Thanks for the brief review of MiniCircuits stuff (I'm not connected with them in any way except as a customer). Since you've characterized some of their parts, perhaps you could help answer a question that someone else posted, and one that I would like to have answered as well. Have you measured the effects of DC current in the windings of an RF transformer, such as is seen if the transformer is in the collector circuit of an amplifier? If so, could you provide a generalization of the effects, such as changes in frequency response, losses, etc.? Many Thanks!, Dave M The very tiny cores on MiniCircuits transformers will start to saturate at hundreds of mA. The effect is that the magnetizing inductance drops, which matters more at low frequencies than high frequencies. I try to avoid feeding DC to an amplifier through a transformer winding. Instead I use a separate RF choke for that. However, it would probably work OK for, say, up to 25 mADC for a small signal transistor, but why take a chance. If you are using a DC feed through a transformer winding, be careful not to accidently short circuit it, causing the full available current from the power supply to flow through the transformer. This can actually magnetize the core and permanently damage it. Saturation via DC is much more deleterious than saturation via AC. It is easy to calculate the flux density using Ampere's law, which is one of the four Maxwell's equations. H = I/(2piR). Since R (radius) is in the denominator, cores saturate from the inside first before the whole core is saturated. Multiply H by mu, (as any time nut knows) to get B. If R is 1 mm, and I is 628 mA, then H = 10 ampere turns per meter. If mu-relative is 1000, then B = 4piX10^-7 X 1000 X 10 = 125 mT. That is a hefty 1250 Gauss. Some materials may be affected at 1/10 this flux density. Now a days, a lot of RF is differential, in which case you are free to feed DC through the output transformer without worrying about this issue. I worked for several companies where those 6 hole cylindrical chokes were ubiquitous. I specifically characterized those and established a maximum current rating of only 100 mA. Of course, many production designs exceeded this limit and worked anyway. I actually observed someone try to put 20A through one of these. The tantalum capacitors on the cold side of the bead actually exploded due to RF current. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
Hi On Nov 28, 2014, at 2:27 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: On 11/28/2014 10:08 AM, Dave M wrote: Rick, Thanks for the brief review of MiniCircuits stuff (I'm not connected with them in any way except as a customer). Since you've characterized some of their parts, perhaps you could help answer a question that someone else posted, and one that I would like to have answered as well. Have you measured the effects of DC current in the windings of an RF transformer, such as is seen if the transformer is in the collector circuit of an amplifier? If so, could you provide a generalization of the effects, such as changes in frequency response, losses, etc.? Many Thanks!, Dave M The very tiny cores on MiniCircuits transformers will start to saturate at hundreds of mA. The effect is that the magnetizing inductance drops, which matters more at low frequencies than high frequencies. I try to avoid feeding DC to an amplifier through a transformer winding. Instead I use a separate RF choke for that. However, it would probably work OK for, say, up to 25 mADC for a small signal transistor, but why take a chance. If you are using a DC feed through a transformer winding, be careful not to accidently short circuit it, causing the full available current from the power supply to flow through the transformer. This can actually magnetize the core and permanently damage it. Saturation via DC is much more deleterious than saturation via AC. It is easy to calculate the flux density using Ampere's law, which is one of the four Maxwell's equations. H = I/(2piR). Since R (radius) is in the denominator, cores saturate from the inside first before the whole core is saturated. Multiply H by mu, (as any time nut knows) to get B. If R is 1 mm, and I is 628 mA, then H = 10 ampere turns per meter. If mu-relative is 1000, then B = 4piX10^-7 X 1000 X 10 = 125 mT. That is a hefty 1250 Gauss. Some materials may be affected at 1/10 this flux density. Now a days, a lot of RF is differential, in which case you are free to feed DC through the output transformer without worrying about this issue. I worked for several companies where those 6 hole cylindrical chokes were ubiquitous. I specifically characterized those and established a maximum current rating of only 100 mA. Of course, many production designs exceeded this limit and worked anyway. I actually observed someone try to put 20A through one of these. The tantalum capacitors on the cold side of the bead actually exploded due to RF current. If you do need to run substantial current through a choke core, the larger binocular cores with a half turn through them are a better choice. Still useless for 20A (or even 2A) though … Bob Rick Karlquist N6RK ___ 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] LTE-Lite
All: After running my 20 MHz LTE-Lite for a week or so, I shut it down and connected one of the 10 MHz units. The LEDs appear to be responding (survey still in progress) as per the quick start guide. Windows installed a new comm port and driver. (COMM6, with FTDI driver) The COMM5 port which was the 20 MHz unit is gone. U-center has selected COMM6 and is autobaud at 38000, but is showing my nothing except blank screens and a red NO FIX. Have I missed something? Or will it not report anything until a lock is achieved?? Thanks, Jim wb4...@amsat.org --- 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] LTE-Lite
Hi The “new chip ID, new com port” thing is pretty typical for the FTDI drivers. If you plug the old LTE back in there’s a good chance it will come back up as COMM 5. Usually they are pretty good about only adding ports for devices they have not seen before. Bob On Nov 28, 2014, at 3:23 PM, Jim Sanford wb4...@wb4gcs.org wrote: All: After running my 20 MHz LTE-Lite for a week or so, I shut it down and connected one of the 10 MHz units. The LEDs appear to be responding (survey still in progress) as per the quick start guide. Windows installed a new comm port and driver. (COMM6, with FTDI driver) The COMM5 port which was the 20 MHz unit is gone. U-center has selected COMM6 and is autobaud at 38000, but is showing my nothing except blank screens and a red NO FIX. Have I missed something? Or will it not report anything until a lock is achieved?? Thanks, Jim wb4...@amsat.org --- 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] Minicircuits 10% discount in December
On 11/28/2014 1:04 PM, Bob Camp wrote: If you do need to run substantial current through a choke core, the larger binocular cores with a half turn through them are a better choice. Still useless for 20A (or even 2A) though … Bob The binocular cores come in several hole sizes. All other things being equal, current handling capacity is directly proportional to hole size. One thing to watch out for with putting DC thru binocular cores happens in push pull RF power amplifiers. The output transformer is usually a binocular core on steroids, or its equivalent constructed with beads or sleeves, etc, threaded over a single turn made from brass tubes connected together at the end away from the transistors. In cheap (illegal) CB amplifiers, you will frequently see +13.6 VDC connected to the junction of the brass tubes, as if it were a center tap. It actually isn't a center tap in terms of core saturation, and the DC currents to the transistors are unmitigated in terms of magnetizing the core. Although the cores are larger, so are the currents, and these amplifiers just live with the degradation including the magnetization. This occurs because each core sees only a half-turn. If you replace the tubes with a 2 turn wire primary, then the problem goes away, but of course then the amplifier would never work as high as 27 MHz, which is does normally only by resonating stray PC board trace inductance with peaking capacitors on the transformer. This forms a two stage step up structure. If you improve the layout to get rid of the trace inductance, the amplifier no longer works! See Motorola AN-762. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
The very tiny cores on MiniCircuits transformers will start to saturate at hundreds of mA. The effect is that the magnetizing inductance drops, which matters more at low frequencies than high frequencies. I try to avoid feeding DC to an amplifier through a transformer winding. Instead I use a separate RF choke for that. However, it would probably work OK for, say, up to 25 mADC for a small signal transistor, but why take a chance. If you are using a DC feed through a transformer winding, be careful not to accidently short circuit it, causing the full available current from the power supply to flow through the transformer. This can actually magnetize the core and permanently damage it. Saturation via DC is much more deleterious than saturation via AC. It is easy to calculate the flux density using Ampere's law, which is one of the four Maxwell's equations. H = I/(2piR). Since R (radius) is in the denominator, cores saturate from the inside first before the whole core is saturated. Multiply H by mu, (as any time nut knows) to get B. If R is 1 mm, and I is 628 mA, then H = 10 ampere turns per meter. If mu-relative is 1000, then B = 4piX10^-7 X 1000 X 10 = 125 mT. That is a hefty 1250 Gauss. Some materials may be affected at 1/10 this flux density. Now a days, a lot of RF is differential, in which case you are free to feed DC through the output transformer without worrying about this issue. I worked for several companies where those 6 hole cylindrical chokes were ubiquitous. I specifically characterized those and established a maximum current rating of only 100 mA. Of course, many production designs exceeded this limit and worked anyway. I actually observed someone try to put 20A through one of these. The tantalum capacitors on the cold side of the bead actually exploded due to RF current. Rick Karlquist N6RK Thanks for the insight, Rick. You confirmed many of my own assumptions about RF transformers and cores. I hadn't thought about permanently magnetizing a core with excessive DC current, but it makes sense. Same theory applies to line frequency power transformers and inductors; if the core saturates, inductance takes a nose-dive and current goes wild. A couple weeks ago, I sent an email to the Minicircuits technical support folks in hopes of getting this, or similar, info about a couple of their transformer models (specifically, T1-1 and T4-1-KK81), but so far, I'm still waiting. Guess I should give them a call.. got great technical advice from them when I called for help some time ago. Cheers, Dave M ___ 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] LTE-Lite
All: Sharing lessons learned the hard way . . . After messing around with my Anti-Virus program, which declared some false threats, messing with drivers, and uninstalling/reinstalling Ublox, I put the 20 MHz unit back on line. Instantly came up and showed data in UBLOX. Shut it down, removed it, and reinstalled the 10 MHz unit which Winders7 called COMM6. Still nothing. Then looked at the LTE-Lite closely -- NMEA was not selected. Selected NMEA. Nothing. Selected COMM6. Nothing. Shifted to 38k4 baud -- instantly had data and a FIX!!! Even though survey LED is still blinking. Fix is pretty close to what I had from the unit that ran a week, PDOP is 1.5 and HDOP is 0.9. Pretty impressive. So, I must conclude that the problem was failure to check the board and make sure NMEA was selected. Hoping to save somebody my pain. 73, Jim wb4...@amsat.org On 11/28/2014 4:23 PM, Jim Sanford wrote: All: After running my 20 MHz LTE-Lite for a week or so, I shut it down and connected one of the 10 MHz units. The LEDs appear to be responding (survey still in progress) as per the quick start guide. Windows installed a new comm port and driver. (COMM6, with FTDI driver) The COMM5 port which was the 20 MHz unit is gone. U-center has selected COMM6 and is autobaud at 38000, but is showing my nothing except blank screens and a red NO FIX. Have I missed something? Or will it not report anything until a lock is achieved?? Thanks, Jim wb4...@amsat.org --- 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. --- 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] Homebrew frequency counter, need help
On 11/27/2014 03:08 PM, lllaaa wrote: Hi guys, I've just get my homebrew counter working. And the resolution seems 10x better than my RACAL DANA 1992. This counter is heavily inspired by the idea from Kasper Pedersen. http://n1.taur.dk/permanent/frequencymeasurement.pdf STM32F051RB EMP240T100C5 do the control and counting job. TDC-GP22 as the interpolator. Linear regression is done by CPU. There are no fancy analog front for both signal path and refclk path. I'm using two SN75ALS176 and the schmitt input of CPLD to do the job. I've noticed that the 10s gate does not get more meaningful digits(looks worse than 1s gate). So here are the questions: 1) I'm wondering if I could say this is an 11 digits/s counter? 2) How can I improve that? Is it limited by the 485 transceiver? I can switch to a faster MCU, that gets more measures per second, but I think that only gets no more than 2 stable bits. A few things to try, and learned: Try measuring the reference against itself, triggering on the same edge you clock the cpld on. If your VCC is wandering, your threshold will wander, and you get wandering phase out of the schmitt trigger in the CPLD. When I built my counter, I had much fun with my 'front end' (AC04s) having variable heating, and thus variable delay, depending on slew rate. I ended up giving each input channel its own low noise regulator to keep crosstalk from going through VCC. I think I calculated that, for a 10MHz 10dBm signal, 6mV threshold error is 100ps. I assume you can pick which edge to trigger on. Measure the reference against itself, and read out interpolator (phase) data on either edge. When I did my counter, I had ground current flowing through the coax between the counter reference input, and the house standard. I had been silly and chosen a low cutoff frequency for the dc-block capacitor in the reference input, which meant that the resulting voltage over the coax shield resistance got through the dc-block, and caused phase modulation. On the rising edge, the noise was low. On the falling edge, it was nasty and wandering, since when you add LF to 10MHz, and then slice it, the pulsewidth varies. From bad experience, try dumping out adjusted timestamps of almost-10MHz, and plot actual timestamp vs predicted timestamp. It will show you if you have 10MHz crosstalk, or, if as I did, you added the interpolator value instead of subtracting it. In my case the counter appeared to work most of the time, while giving wrong readings all of the time. And congratulations on getting it working. /Kasper Pedersen (When getting 10MHz out of FEI5680As, mine had ferrite blocks around the dsub connectors, and while I could get a cleaner signal by shorting GND to shield on the connector, it was better again when I bypassed the connector entirely and ran coax.) ___ 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] thoughts on lightning arrestors
On 11/28/2014 6:57 PM, Bob Camp wrote: /A mountain top (or skyscraper top) communications setup can be designed to// //take multiple direct lightning hits an hour and keep right on going and do// //it for may years. There are//*lots*// of systems out there like that./ Last April 25 there was a direct hit on the St. Pietro church in the State of Vatican in Rome... http://www.meteoweb.eu/wp-content/uploads/2014/04/fulmine-San-Pietro.jpg No damages whatsoever reported. But one could always argue that that church enjoys a special level of protection :-) 73 Alberto I2PHD --- 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] LTE-Lite
kb...@n1k.org said:
The ânew chip ID, new com portâ thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in thereâs a good chance it will come
back up as COMM 5. Usually they are pretty good about only adding ports for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
lsusb -v will show things like:
idVendor 0x0403 Future Technology Devices International, Ltd
idProduct 0x6001 FT232 USB-Serial (UART) IC
bcdDevice6.00
iManufacturer 1 FTDI
iProduct2 FT232R USB UART
iSerial 3 A102GX1N
/var/log/messages or /var/log/syslog will contain something like:
Nov 28 15:12:00 deb kernel: [1392082.791230] usb 3-3: Product: FT232R USB UART
Nov 28 15:12:00 deb kernel: [1392082.791235] usb 3-3: Manufacturer: FTDI
Nov 28 15:12:00 deb kernel: [1392082.791240] usb 3-3: SerialNumber: A102GX1N
Nov 28 15:12:00 deb kernel: [1392082.799337] ftdi_sio 3-3:1.0: FTDI USB
Serial Device converter detected
Nov 28 15:12:00 deb kernel: [1392082.799447] usb 3-3: Detected FT232RL
...
Nov 28 15:12:00 deb kernel: [1392082.805436] usb 3-3: FTDI USB Serial Device
converter now attached to ttyUSB3
This is what I put in /etc/udev/rules.d/35-hgm.rules
# LTE LITE Eval Board
KERNEL==ttyUSB*, ATTRS{serial}==A102GX1N, MODE=0666, SYMLINK+=LITE
I use the same approach with my Rigol scope and Prologic USB-GPIB.
--
These are my opinions. I hate spam.
___
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] Low cost oscillator packages
Assume the temperature is stable and the power supply is clean and we aren't testing one of the PLL units and ... What's the ADEV and/or phase noise of a typical low cost oscillator package? Are there slightly more expensive parts that are a lot better? Is there something in the data sheets to look for? What sort of toys do I need to measure ADEV and/or phase noise? I'm interested in hobby prices rather than expensive high-end gear. -- These are my opinions. I hate spam. ___ 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] Minicircuits 10% discount in December
Am 28.11.2014 um 23:42 schrieb Dave M: A couple weeks ago, I sent an email to the Minicircuits technical support folks in hopes of getting this, or similar, info about a couple of their transformer models (specifically, T1-1 and T4-1-KK81), but so far, I'm still waiting. Guess I should give them a call.. got great technical advice from them when I called for help some time ago. Try that: http://lmgtfy.com/?q=T1-1-KK81.pdf The first anwer looks like a hit. regards, Gerhard ___ 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] Homebrew frequency counter, need help
On Fri, 28 Nov 2014 21:04:27 +0800, you wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; Hi, That's very interesting. I've been planning to do a basic board with a GP22 for a while - something like the acam evaluation board but with some input circuitry, and plugged into a fast microcontroller board. Could not decide what one, so I thought that an arduino-type board would be the most flexible for now. I mainly just want to test it until it squeaks. Now that winter is coming and I've got all the bits, I'll hopefully get time to do it. First job is QFN soldering. That should be fun I thought it looked like setting up the registers could be a bit of a problem. The manual for the evaluation kit says that there are some example setups included - I did wonder if it might be possible to see that and other info if the software was installed and run, even without their board connected, but did not try that yet. Angus. 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. ___ 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] Minicircuits 10% discount in December
Gerhard Hoffmann wrote: Am 28.11.2014 um 23:42 schrieb Dave M: A couple weeks ago, I sent an email to the Minicircuits technical support folks in hopes of getting this, or similar, info about a couple of their transformer models (specifically, T1-1 and T4-1-KK81), but so far, I'm still waiting. Guess I should give them a call.. got great technical advice from them when I called for help some time ago. Try that: http://lmgtfy.com/?q=T1-1-KK81.pdf The first anwer looks like a hit. regards, Gerhard Thanks Gerhard, but I can't get that link to work. It sends me to Google, which tells me that I need to enable Javascript. Javascript has been turned on and running on my system for years, but apparently, that link doesn't see it. Dave M ___ 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] eBay seller has Z3801A upgraded to 58503A
On Fri, Nov 28, 2014 at 12:23 AM, Said Jackson via time-nuts time-nuts@febo.com wrote: Plus the Z3801A seems to just work. On the Lucent boxes we had to suffer through many 100's of posts over the last month... To be fair there doesn't seem to be a 3810 manual so some details needed sorting out. But, given a complete Z3810AS, Stewart's original post is enough to get to the 'just work' phase if the boxes are functioning and the quick check phase if they're broken. ___ 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] Minicircuits 10% discount in December
Hi On Nov 28, 2014, at 8:48 PM, Dave M dgmin...@mediacombb.net wrote: Gerhard Hoffmann wrote: Am 28.11.2014 um 23:42 schrieb Dave M: A couple weeks ago, I sent an email to the Minicircuits technical support folks in hopes of getting this, or similar, info about a couple of their transformer models (specifically, T1-1 and T4-1-KK81), but so far, I'm still waiting. Guess I should give them a call.. got great technical advice from them when I called for help some time ago. Try that: http://lmgtfy.com/?q=T1-1-KK81.pdf The first anwer looks like a hit. regards, Gerhard Thanks Gerhard, but I can't get that link to work. It sends me to Google, which tells me that I need to enable Javascript. Javascript has been turned on and running on my system for years, but apparently, that link doesn't see it. The link animates a Google search for the part number. The first thing that comes up here is the standard Mini-Circuits spec sheet for the part. It’s got the usual S parameter data, but nothing on DC current. Bob Dave M ___ 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] Homebrew frequency counter, need help
On Fri, 28 Nov 2014 08:57:37 -0600, you wrote: Hi On Nov 28, 2014, at 7:04 AM, Li Ang lll...@gmail.com wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). Which is a very good reason to play with it TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. Hi , Unfortunately the 22ps etc is just resolution and there is also a fair bit of noise - some typical SD's are given in the data sheet which vary from 35 to 72 ps depending on the settings, and that only covers part of the range. 60ps RMS noise is also mentioned. The nominal clock input is 2-8MHz, but the 22ps range is only available for clocks 6MHz, and not in Mode1 which is being used. Should still be enough to give most counters a workout. Angus. The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. This may be the resolution / accuracy thing I mentioned above. Dont give up quite yet though. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Gee that sounds like the documentation on a LOT of parts these days . Its also what keeps people from trying this sort of thing. A few hardware questions: 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) 2) Is there more bypassing on the circuit than shown? (If not, add some more). 3) How confident are you of your input signal? (can you check it with a known good counter?) 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things ) A full counter will have a bit more stuff than just this chip. I think getting this part working *before* you work on the rest of it is a very good idea. One small piece at a time . Bob Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; ? 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. tdc_gp22.GIF___ 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] USB Serial ports, was Re: LTE-Lite
Hi,
For Windows, ComPortMan does a great job of managing comm port
assignments. Available at http://www.uwe-sieber.de/comportman_e.html
Cheers,
david
On 29/11/2014 9:42 AM, Hal Murray wrote:
kb8tq-wyfad0z3...@public.gmane.org said:
The “new chip ID, new com port†thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will come
back up as COMM 5. Usually they are pretty good about only adding ports for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
lsusb -v will show things like:
idVendor 0x0403 Future Technology Devices International, Ltd
idProduct 0x6001 FT232 USB-Serial (UART) IC
bcdDevice6.00
iManufacturer 1 FTDI
iProduct2 FT232R USB UART
iSerial 3 A102GX1N
/var/log/messages or /var/log/syslog will contain something like:
Nov 28 15:12:00 deb kernel: [1392082.791230] usb 3-3: Product: FT232R USB UART
Nov 28 15:12:00 deb kernel: [1392082.791235] usb 3-3: Manufacturer: FTDI
Nov 28 15:12:00 deb kernel: [1392082.791240] usb 3-3: SerialNumber: A102GX1N
Nov 28 15:12:00 deb kernel: [1392082.799337] ftdi_sio 3-3:1.0: FTDI USB
Serial Device converter detected
Nov 28 15:12:00 deb kernel: [1392082.799447] usb 3-3: Detected FT232RL
Nov 28 15:12:00 deb kernel: [1392082.805436] usb 3-3: FTDI USB Serial Device
converter now attached to ttyUSB3
This is what I put in /etc/udev/rules.d/35-hgm.rules
# LTE LITE Eval Board
KERNEL==ttyUSB*, ATTRS{serial}==A102GX1N, MODE=0666, SYMLINK+=LITE
I use the same approach with my Rigol scope and Prologic USB-GPIB.
___
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] Homebrew frequency counter, need help
On Nov 28, 2014, at 9:18 PM, Angus not.ag...@btinternet.com wrote: On Fri, 28 Nov 2014 08:57:37 -0600, you wrote: Hi On Nov 28, 2014, at 7:04 AM, Li Ang lll...@gmail.com wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). Which is a very good reason to play with it TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. Hi , Unfortunately the 22ps etc is just resolution and there is also a fair bit of noise - some typical SD's are given in the data sheet which vary from 35 to 72 ps depending on the settings, and that only covers part of the range. 60ps RMS noise is also mentioned. The nominal clock input is 2-8MHz, but the 22ps range is only available for clocks 6MHz, and not in Mode1 which is being used. Should still be enough to give most counters a workout. Hi As long as the one sigma point is below 100 ps, that’s not a disaster for turning it into a counter. It’s not going to beat out a SR 620, but it’s still a very respectable device. Being able to do it all with a handful of parts and at 1 to 3% of the cost of a new counter is pretty impressive. Assuming that the counter timebase is 10 MHz, a clock into the chip of 5, 3.333, or 2.5 MHz could be done quite easily. It sounds like they all would hit the 2 to 8 MHz range needed. Bob Angus. The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. This may be the resolution / accuracy thing I mentioned above. Dont give up quite yet though. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Gee that sounds like the documentation on a LOT of parts these days . Its also what keeps people from trying this sort of thing. A few hardware questions: 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) 2) Is there more bypassing on the circuit than shown? (If not, add some more). 3) How confident are you of your input signal? (can you check it with a known good counter?) 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things ) A full counter will have a bit more stuff than just this chip. I think getting this part working *before* you work on the rest of it is a very good idea. One small piece at a time . Bob Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; ? 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. tdc_gp22.GIF___ 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] Truetime GPS-DC-416 specs ?
Thanks guys, It was just a matter of curiosity, there's one locally for sale on ebay and I hadn't seen one before :) cheers Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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] LTE-Lite
On Fri, Nov 28, 2014 at 3:42 PM, Hal Murray hmur...@megapathdsl.net wrote: kb...@n1k.org said: The “new chip ID, new com port” thing is pretty typical for the FTDI drivers. If you plug the old LTE back in there’s a good chance it will come back up as COMM 5. Usually they are pretty good about only adding ports for devices they have not seen before. Most/some of the FTDI usb to serial chips have a serial number. I don't know how it works on Windows, but on Linux, you can use the udev rules to make an alias so your software can refer to something with a filename like /dev/LITE rather than /dev/ttyUSB2. It works no matter which slot you plug it into and/or still works after it gets unplugged and reconnected. It's really a limitation of USB. You have the vendor ID, product ID, and for some devices, a serial number. IF the device has a serial number, next time it's plugged in, the OS can be pretty certain it's the same device and can use the same COM port or device assignment as last time. If not, all bets are off. If a USB device has no serial number, Windows choses to use the physical USB port the device is plugged into. I.e. if you plug such a device with the same vendor ID/product ID into the same USB port, you get the same COM port assignment. I really don't know of a better way. It's unfortunate that for a device with no serial number, if you plug the same device into a different USB port, you get a different COM port, but it is the best solution for the case where you have more than one USB device with the same vendor ID/product ID... it works just the same as traditional RS232 ports: the COM port assignment depends on which socket you plug the device in. It is also unfortunate that the USB specs allowed this to happen and didn't require devices to have a serial number. ___ 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] LTE-Lite
For Linux, I worked this up and posted to linuxquestions.org. I don't
guarantee it, but it's been working for the PL-2303 devices for me. It just
creates a link to the real driver. There are probably better ways to do it.
File: /etc/udev/rules.d/70-persistent-usb.rulesACTION==add,
KERNEL==ttyUSB[0-9]*, PROGRAM=/etc/udev/rules.d/usb-parse-devpath.pm %p,
SYMLINK+=ttyUSB%c
File: /etc/udev/rules.d/usb-parse-devpath.pm#!/usr/bin/perl -w
@items = split(/, $ARGV[0]);
for ($i = 0; $i @items; $i++) {
if ($items[$i] =~ m/^usb[0-9]+$/) {
if ($items[$i + 2] =~ m/:/) {
print $items[$i + 1] . \n;
} else {
print $items[$i + 2] . \n;
}
last;
}
}
Example:
crw-rw 1 root dialout 188, 0 Nov 28 20:59 /dev/ttyUSB0
crw-rw 1 root dialout 188, 1 Nov 28 23:43 /dev/ttyUSB1
lrwxrwxrwx 1 root root 7 Nov 17 23:39 /dev/ttyUSB1-2 - ttyUSB0
lrwxrwxrwx 1 root root 7 Nov 22 21:17 /dev/ttyUSB4-2 - ttyUSB1
If the two code boxes don't make it through the list forwarder, the code can be
found here. Read the whole thread as I didn't put it all in the final post:
www.linuxquestions.org/questions/linux-hardware-18/usb-pl2303-reliable-device-names-4175506134/
Bob
From: Orin Eman orin.e...@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Friday, November 28, 2014 11:41 PM
Subject: Re: [time-nuts] LTE-Lite
On Fri, Nov 28, 2014 at 3:42 PM, Hal Murray hmur...@megapathdsl.net wrote:
kb...@n1k.org said:
The “new chip ID, new com port” thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will
come
back up as COMM 5. Usually they are pretty good about only adding ports
for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't
know
how it works on Windows, but on Linux, you can use the udev rules to make
an
alias so your software can refer to something with a filename like
/dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
It's really a limitation of USB. You have the vendor ID, product ID, and
for some devices, a serial number.
IF the device has a serial number, next time it's plugged in, the OS can be
pretty certain it's the same device and can use the same COM port or device
assignment as last time. If not, all bets are off.
If a USB device has no serial number, Windows choses to use the physical
USB port the device is plugged into. I.e. if you plug such a device with
the same vendor ID/product ID into the same USB port, you get the same COM
port assignment. I really don't know of a better way. It's unfortunate
that for a device with no serial number, if you plug the same device into a
different USB port, you get a different COM port, but it is the best
solution for the case where you have more than one USB device with the same
vendor ID/product ID... it works just the same as traditional RS232 ports:
the COM port assignment depends on which socket you plug the device in.
It is also unfortunate that the USB specs allowed this to happen and didn't
require devices to have a serial number.
___
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] 10 MHz Filters
John wrote: For the most part, you don't want transformer isolation unless you plan on using balanced lines. There are worse things than ground loops out there, and lifting a coax shield away from ground is a great way to find all of them. You certainly need the shield grounded at RF, but you don't necessarily need it grounded all the way down to DC. A fairly common solution that works well for many applications is to use isolated connectors (not connected directly to the chassis) with a 10nF capacitor from each connector shield to the chassis immediately adjacent to the connector. The capacitor grounds the shield at RF but allows very little current to flow at the mains frequency. NOTE: You want the bypass capacitor right at the connector, to make sure the RFI current loop is tiny and cannot radiate. That said, I often build distribution amplifiers with chassis-grounded connectors and have never had ground loop problems. But then, I pretty much always design transformer-isolated DC supplies with low-field transformers and linear regulators into everything I build, and do not use wall-warts, desk-warts, or switching supplies. If one were building the dist amp I posted the other day and wanted to use chassis-grounded connectors, the per-stage transformers could be simplified from 1:1:1 to 1:1 -- omitting the third winding -- with the transistor collectors capacitor-coupled to the output connectors. In this case, I would put ~100k resistors across each output to hold the connector ends of the capacitors at 0v even with an open load. For isolation amplifiers used with mixer-type frequency comparators, which can be very sensitive to ground loops because of the low mixer output frequency, I do use RF transformers and bypass the shields to chassis. You definitely don't want 10.7 MHz IF transformers, unless you are just trying to build a thermometer. Hear, hear. 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.
