Re: [time-nuts] Don't use cheap cables -- a cautionary tale (Bob Camp)
On 5 March 2013 17:08, Gregory Muir engineer...@mt.net wrote: When I compare the typical easily-obtained Jameco or Marlin P Jones type of connector to a better made product such as a true MIL item on a network analyzer, one can see a noticeable difference between the impedance and VSWR characteristics. It has been long known that the simple nickel-plate connector can cause problems over time in an installation from changing contact resistance and such. The manufacturer RF Industries still uses silver gold plating on their types of RF connectors as compared to the cheaper nickel-plated types and I have found these to be very reliable with a cost slightly higher than the cheaper nickel plated types. I've recently been playing with some N adapters from various manufacturers. I was particularly keen to find a decent male to male adapter to include with a low-cost N calibration and verification kit I am sellling. http://www.vnacalibration.co.uk/sales/ If you read the specs on that, I state if the male to male adapter is used, it limits performance. I've tried various makes, from the cheap to fairly expensive (Huber and Suhner), although I am not considering metrology grade devices, given the price I am selling the kit for. I don't have all the data in front of me, but certain things stick in my mind. 1) The Huber and Suhner female-female N barrel was the most expensive of any I tried. The qualtiy of the threads was excellent. But when I stuck it on the VNA, the performance was really poor. I was intending to phone H+S to ask what was wrong, but before doing so I looked at the specification sheet. The spec was indeed poor, and the one I had met it. 2) Someone recently sent me a couple of RF Industries male to male N barrel adapters. RF performance was higher than I had seen on any connector of its type with the exception of metrology grade devices. However, it felt as though there was sand between the threads when tightening these up. 3) I found some pretty decent female-female Ns that were really cheap ( $5). RF performance was good, mechanically well made. They did not have the best RF performance of those I found, but they were cheap. For a male-male adapter in that cal kit, I have settled on the Radiall component for now, but I'd like to find a better one. The RF Industries unit would do, as long as I supply a lubricant to make screwing the things on better. So to me, there does not appear to much correlation between cost and performance. I've seen poor expensive items and fairly decent very cheap items. 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] Don't use cheap cables -- a cautionary tale (Bob Camp)
At what frequency do these problems appear? And how bad it bad? -Original Message- From: David Kirkby david.kir...@onetel.net Sender: time-nuts-boun...@febo.com Date: Tue, 5 Mar 2013 18:16:54 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale (Bob Camp) On 5 March 2013 17:08, Gregory Muir engineer...@mt.net wrote: When I compare the typical easily-obtained Jameco or Marlin P Jones type of connector to a better made product such as a true MIL item on a network analyzer, one can see a noticeable difference between the impedance and VSWR characteristics. It has been long known that the simple nickel-plate connector can cause problems over time in an installation from changing contact resistance and such. The manufacturer RF Industries still uses silver gold plating on their types of RF connectors as compared to the cheaper nickel-plated types and I have found these to be very reliable with a cost slightly higher than the cheaper nickel plated types. I've recently been playing with some N adapters from various manufacturers. I was particularly keen to find a decent male to male adapter to include with a low-cost N calibration and verification kit I am sellling. http://www.vnacalibration.co.uk/sales/ If you read the specs on that, I state if the male to male adapter is used, it limits performance. I've tried various makes, from the cheap to fairly expensive (Huber and Suhner), although I am not considering metrology grade devices, given the price I am selling the kit for. I don't have all the data in front of me, but certain things stick in my mind. 1) The Huber and Suhner female-female N barrel was the most expensive of any I tried. The qualtiy of the threads was excellent. But when I stuck it on the VNA, the performance was really poor. I was intending to phone H+S to ask what was wrong, but before doing so I looked at the specification sheet. The spec was indeed poor, and the one I had met it. 2) Someone recently sent me a couple of RF Industries male to male N barrel adapters. RF performance was higher than I had seen on any connector of its type with the exception of metrology grade devices. However, it felt as though there was sand between the threads when tightening these up. 3) I found some pretty decent female-female Ns that were really cheap ( $5). RF performance was good, mechanically well made. They did not have the best RF performance of those I found, but they were cheap. For a male-male adapter in that cal kit, I have settled on the Radiall component for now, but I'd like to find a better one. The RF Industries unit would do, as long as I supply a lubricant to make screwing the things on better. So to me, there does not appear to much correlation between cost and performance. I've seen poor expensive items and fairly decent very cheap items. 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] Don't use cheap cables -- a cautionary tale (Bob Camp)
On 6 March 2013 11:33, li...@lazygranch.com wrote: At what frequency do these problems appear? And how bad it bad? My interest for VNA calibration and verification kits is probably well outside most time-nut uses. I normally test N connectors from 50 MHz to 6 GHz. 50 MHz is the lower limit of my HP 8720D (20 GHz) VNA and 6 GHz is the upper limited of my N calibration kit (HP 85032B). To give a couple of figures. 1) Huber and Suhner female-female barrel, which is the most expensive I tried (15.26 GBP), has a worst case return loss of just 17.2 dB. 2) TE Connectivity the cheapest I tried at just £2.84 GBP, had a return loss of 35.1 dB. 2) Telegartner, mid-priced at 6.68 GBP had a return loss of 38.9 dB. So a mid-priced one was better than both the expensive and cheapest choice. All are based on a saaple of two, and worst case results quoted above. I did not find much variation between two of the same manufacturer. Although I don't have exact data in front of me, as I'd need to go through the individual data files which I can't be bothered to do, all were very good at low frequencies (say 500 MHz or less). The worst case is not always at the highest frequency, although the performance at 6 GHz is always worst than at 50 MHz. All data was colllected by use of * HP 8720D VNA within its calibration period. * Agilent 3.5 mm test port cables on the VNA (over $5000 a pair) * Metrology grade 3.5 mm to N adapters * HP 85032B N calibration kit. Since the N calibration kit was after the metrology grade 3.5 mm - N adapters, any issues with those adapters would be removed by the VNA calibration routine. I've seen some Americans make comments like if it does not have Ampenol printed on it, then avoid it. I'm not German, but the mid-priced German made Telegartner F-F adapter was the best. See pictures at the bottom of http://www.vnacalibration.co.uk/support/NCV032B/HP/ For qualtiy of the threads, the Chinese made Huber and Suhner device was the best, but it was by far the most expensive. The 85032B comes with 4 APC-7 to N metrology grade adapters. They can be assembled to make any N adapter you want (male-female, male-male, female-female). These always provide better peformance than any commerical grade connectors I mention above, but such devices are far too expensive for the kit I use, which I sell at less than the price of the adapters. I would never use an adapter for a critical high frequency application without testing it first. BTW, I used to work in a Ministry of Defence calibration lab in the UK. They always removed the rubber washers in N connectors. I notice the metrology grade adapters don't have these, and Joel Dunsmore, Agilent top VNA guru, reccomeneds in his book on VNAs to do the same. Dave -Original Message- From: David Kirkby david.kir...@onetel.net Sender: time-nuts-boun...@febo.com Date: Tue, 5 Mar 2013 18:16:54 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale (Bob Camp) On 5 March 2013 17:08, Gregory Muir engineer...@mt.net wrote: When I compare the typical easily-obtained Jameco or Marlin P Jones type of connector to a better made product such as a true MIL item on a network analyzer, one can see a noticeable difference between the impedance and VSWR characteristics. It has been long known that the simple nickel-plate connector can cause problems over time in an installation from changing contact resistance and such. The manufacturer RF Industries still uses silver gold plating on their types of RF connectors as compared to the cheaper nickel-plated types and I have found these to be very reliable with a cost slightly higher than the cheaper nickel plated types. I've recently been playing with some N adapters from various manufacturers. I was particularly keen to find a decent male to male adapter to include with a low-cost N calibration and verification kit I am sellling. http://www.vnacalibration.co.uk/sales/ If you read the specs on that, I state if the male to male adapter is used, it limits performance. I've tried various makes, from the cheap to fairly expensive (Huber and Suhner), although I am not considering metrology grade devices, given the price I am selling the kit for. I don't have all the data in front of me, but certain things stick in my mind. 1) The Huber and Suhner female-female N barrel was the most expensive of any I tried. The qualtiy of the threads was excellent. But when I stuck it on the VNA, the performance was really poor. I was intending to phone H+S to ask what was wrong, but before doing so I looked at the specification sheet. The spec was indeed poor, and the one I had met it. 2) Someone recently sent me a couple of RF Industries male to male N barrel adapters. RF performance was higher than I had seen
Re: [time-nuts] Don't use cheap cables -- a cautionary tale (Bob Camp)
I'm weighing in a little late on this one but wanted to make a few comments regarding cables and connectors in hopes that a prior poster may not have covered these thoughts. With regards to single-shield coaxial cables, I think we are all aware that shielding effectiveness can vary widely between cables of the same type. I have seen cable shielding as bad as 50% and as good approaching 90%. Of course, anything below 100% means that they are leaky - for either inward or outward bound signals. But one little cautionary indication as to the quality of the cable and its shielding is stamped on the cable itself. If you see a description saying RG-xx Type, you are basically dealing with a cable of which the manufacturer is saying that it is like that specific type of cable but does not necessarily meet the specifications one would expect. So, if you want a cable to meet a certain quality, use a cable without the Type designation. In your posting, you mentioned the words radio room. That in itself is a red flag meaning possible sources of strong RF. In situations like that you must make sure that any circuits requiring good isolation from other interfering sources must contain adequate shielding be it circuit- or cable-wise. I think we all are aware of that consideration. I have seen instances of strong enough RF sources actually setting up circulating currents in adjacent coaxial cable shields that couples the stray power into the innocent cable and also affects the impedance characteristics of same. This has also been seen in the larger solid copper transmission lines as well as microwave waveguides. With regards to connector selection, during my life in Colorado working with the US government, I once attended a RF connector course at the (then) NBS. It was quite an eye opener with regards to the connect-disconnect cycle life of the typical coaxial cable connector. If you want a reliable connection, don't start with a worn connector. And the choice of manufacturer of the connector can be as important as well with regards to the construction and plating materials used. When I compare the typical easily-obtained Jameco or Marlin P Jones type of connector to a better made product such as a true MIL item on a network analyzer, one can see a noticeable difference between the impedance and VSWR characteristics. It has been long known that the simple nickel-plate connector can cause problems over time in an installation from changing contact resistance and such. The manufacturer RF Industries still uses silver gold plating on their types of RF connectors as compared to the cheaper nickel-plated types and I have found these to be very reliable with a cost slightly higher than the cheaper nickel plated types. Greg -- Message: 1 Date: Mon, 4 Mar 2013 07:28:19 -0500 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Message-ID: 7ad45ad9-6965-4f7a-b683-d75902992...@rtty.us Content-Type: text/plain; charset=us-ascii Hi Termination is important. An open cable typically reflects energy down both the inside and outside of the shield. I'd bet the same thing is true to a much lesser extent of an open T connector. The list of nasties is quite long, so there is no one magic thing that fixes all problems. Bob On Mar 3, 2013, at 10:36 PM, Mark Spencer mspencer12...@yahoo.ca wrote: This is a useful thread IMHO. Re the continuous beat note interference issue, I believe I've encountered this when evaluating a Datum1000B. At first I saw a periodic change in frequency of several E-10, the typical period was several hundred seconds. Turning off all the un needed gear in my lab except for a few ocxo's that i don't want to turn off and using double shielded RG400 cables without adapters for all the interconnections seemed to make the issue go away. All the outputs from the un used ocxo's were also terminated with bnc or sma terminators.Even the BNC T connectors I typically leave connected to the inputs of my HP5370B's (along with 50 ohm terminators) seemed to cause issues in this application. This issue has also prompted me to give up on my plans to move my GPSDO's from my radio room to my lab, as it's nice to be able to leave the GPSDO's running into a terminator vs having to shut them off. I've never really put much effort into tracking down the root cause of this issue but I suspect it is similar to what John mentioned. My FTS1050 (which IIRC is based on a datum 1000) doesn't seem to have this issue, building enclosures for my Datum1000's is on my post retirement to do list as I suspect running them without an enclosure may be contributing to this problem. As far as I know my BVA Ocxo is immune from this issue as well. Regards Mark Spencer
Re: [time-nuts] Don't use cheap cables -- a cautionary tale (BobCamp)
Hi Not quite sure how my name got into the thread title... Coverage numbers aren't all they might be. A simple aluminum foil wrap lets a vendor claim 100% coverage. The skin depth of the foil is near zero, so it's not a big help shield wise at low frequencies. Same thing with labels, just about any fly by night outfit can write nearly anything on a cable. Skin depth at 1 MHz is about 0.1 mm (4 mils). At that point, shielding is compromised. Depending on cable length / required isolation / optical coverage you might want 5 or even 10 skin depths. It's a bit tough to find a flexible lab cable with 1 mm (40 mil) shielding on it. As you go down in frequency, at some point your only real solution is a twisted pair. Before that point, multiple isolated shields can help (good luck with connectors). At 1 Hz (1 pps ..) you would need 0.1 m of shield to get to one skin depth. That's not a cable I have in stock... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Gregory Muir Sent: Tuesday, March 05, 2013 12:08 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale (BobCamp) I'm weighing in a little late on this one but wanted to make a few comments regarding cables and connectors in hopes that a prior poster may not have covered these thoughts. With regards to single-shield coaxial cables, I think we are all aware that shielding effectiveness can vary widely between cables of the same type. I have seen cable shielding as bad as 50% and as good approaching 90%. Of course, anything below 100% means that they are leaky - for either inward or outward bound signals. But one little cautionary indication as to the quality of the cable and its shielding is stamped on the cable itself. If you see a description saying RG-xx Type, you are basically dealing with a cable of which the manufacturer is saying that it is like that specific type of cable but does not necessarily meet the specifications one would expect. So, if you want a cable to meet a certain quality, use a cable without the Type designation. In your posting, you mentioned the words radio room. That in itself is a red flag meaning possible sources of strong RF. In situations like that you must make sure that any circuits requiring good isolation from other interfering sources must contain adequate shielding be it circuit- or cable-wise. I think we all are aware of that consideration. I have seen instances of strong enough RF sources actually setting up circulating currents in adjacent coaxial cable shields that couples the stray power into the innocent cable and also affects the impedance characteristics of same. This has also been seen in the larger solid copper transmission lines as well as microwave waveguides. With regards to connector selection, during my life in Colorado working with the US government, I once attended a RF connector course at the (then) NBS. It was quite an eye opener with regards to the connect-disconnect cycle life of the typical coaxial cable connector. If you want a reliable connection, don't start with a worn connector. And the choice of manufacturer of the connector can be as important as well with regards to the construction and plating materials used. When I compare the typical easily-obtained Jameco or Marlin P Jones type of connector to a better made product such as a true MIL item on a network analyzer, one can see a noticeable difference between the impedance and VSWR characteristics. It has been long known that the simple nickel-plate connector can cause problems over time in an installation from changing contact resistance and such. The manufacturer RF Industries still uses silver gold plating on their types of RF connectors as compared to the cheaper nickel-plated types and I have found these to be very reliable with a cost slightly higher than the cheaper nickel plated types. Greg -- Message: 1 Date: Mon, 4 Mar 2013 07:28:19 -0500 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Message-ID: 7ad45ad9-6965-4f7a-b683-d75902992...@rtty.us Content-Type: text/plain; charset=us-ascii Hi Termination is important. An open cable typically reflects energy down both the inside and outside of the shield. I'd bet the same thing is true to a much lesser extent of an open T connector. The list of nasties is quite long, so there is no one magic thing that fixes all problems. Bob On Mar 3, 2013, at 10:36 PM, Mark Spencer mspencer12...@yahoo.ca wrote: This is a useful thread IMHO. Re the continuous beat note interference issue, I believe I've encountered this when evaluating a Datum1000B. At first I saw a periodic change in frequency of several E-10
Re: [time-nuts] Don't use cheap cables -- a cautionary tale
Hi Termination is important. An open cable typically reflects energy down both the inside and outside of the shield. I'd bet the same thing is true to a much lesser extent of an open T connector. The list of nasties is quite long, so there is no one magic thing that fixes all problems. Bob On Mar 3, 2013, at 10:36 PM, Mark Spencer mspencer12...@yahoo.ca wrote: This is a useful thread IMHO. Re the continuous beat note interference issue, I believe I've encountered this when evaluating a Datum1000B. At first I saw a periodic change in frequency of several E-10, the typical period was several hundred seconds. Turning off all the un needed gear in my lab except for a few ocxo's that i don't want to turn off and using double shielded RG400 cables without adapters for all the interconnections seemed to make the issue go away. All the outputs from the un used ocxo's were also terminated with bnc or sma terminators.Even the BNC T connectors I typically leave connected to the inputs of my HP5370B's (along with 50 ohm terminators) seemed to cause issues in this application. This issue has also prompted me to give up on my plans to move my GPSDO's from my radio room to my lab, as it's nice to be able to leave the GPSDO's running into a terminator vs having to shut them off. I've never really put much effort into tracking down the root cause of this issue but I suspect it is similar to what John mentioned. My FTS1050 (which IIRC is based on a datum 1000) doesn't seem to have this issue, building enclosures for my Datum1000's is on my post retirement to do list as I suspect running them without an enclosure may be contributing to this problem. As far as I know my BVA Ocxo is immune from this issue as well. Regards Mark Spencer Sent from my iPad ___ 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] Don't use cheap cables -- a cautionary tale
Hi By any chance is the connector a BNC? They have been known to create similar looking issues. Bob On Mar 3, 2013, at 9:59 AM, John Ackermann j...@febo.com wrote: I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds. I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot. The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem. Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. John austron-fts-beat-note.png___ 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] Don't use cheap cables -- a cautionary tale
Yup, they are BNC (by necessity). I'm still experimenting but it may be an ill-fitting connector on the cheap patch cable. Switching to a better quality cable seems to have solved the problem, one way or the other. John Bob Camp said the following on 03/03/2013 10:10 AM: Hi By any chance is the connector a BNC? They have been known to create similar looking issues. Bob On Mar 3, 2013, at 9:59 AM, John Ackermann j...@febo.com wrote: I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds. I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot. The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem. Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. John austron-fts-beat-note.png___ 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] Don't use cheap cables -- a cautionary tale
On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. Kevin ___ 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] Don't use cheap cables -- a cautionary tale
Hi BNC's suffer from shield separation issues and from basic wear out on the connector it's self. Cheap coax = shield seperation. On the connector its self it's either plating or loss of spring in the fingers. The best solution is to cut the connector off the cable. That way at least it doesn't mess you up a second time. Once you get a big enough pile of single ended cables, it's time to get out the crimp tool…. Bob On Mar 3, 2013, at 10:46 AM, John Ackermann j...@febo.com wrote: Yup, they are BNC (by necessity). I'm still experimenting but it may be an ill-fitting connector on the cheap patch cable. Switching to a better quality cable seems to have solved the problem, one way or the other. John Bob Camp said the following on 03/03/2013 10:10 AM: Hi By any chance is the connector a BNC? They have been known to create similar looking issues. Bob On Mar 3, 2013, at 9:59 AM, John Ackermann j...@febo.com wrote: I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds. I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot. The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem. Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. John austron-fts-beat-note.png___ 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] Don't use cheap cables -- a cautionary tale
On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
Hi, The use of double shielded cables does raise the question to what type of connectors to use? Regards, Henk Op 3 mrt. 2013 om 17:30 heeft Jim Lux jim...@earthlink.net het volgende geschreven: On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
Yes, we all have to learn that lesson... At the time I use bedea RG-223 and Belden H155 with soldered and crimped Telegaertner BNC connectors as general purpose cable (up to 2 GHz). Above that frequency I wouldn't use BNC. If you simply connect your tracking generator with the spectrum analyzer by using such a BNC cable there's not one that is absolutely stable when stressing the connector. I tried several manufacturers, HP, Suhner, Radiall, Rosenberger, it's always the same. To make precise measurements I prefer screwed connectors like N or SMA. Volker Am 03.03.2013 17:30, schrieb Jim Lux: On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
I could not agree more, having been burned once or twice. One batch of 50 Ohm cables was clearly marked 75 Ohms when received. These used some form of relatively high resistance foil shield and a drain wire for the outer conductor. The high resistance permitted a ground loop with hum on my 10 MHz reference thus FMing my signal generator. A couple of things to note: Measure the DC resistance between the connector bodies it should be way less than 1 Ohm, perhaps 0.1 ohm above what you see with the probes shorted. The previous regarding RG-58 apply unless the cable is labeled with a manufacturers part number and that is stated in the vendors spec - Such as BELDEN 8262 RG-58U Coaxial BNC M/M Patch Cable 10FT. RG58 C/U MIL C17 50 OHMS stamped on the cable. These were from - Digital Connections - cablesellforl...@yahoo.com and purchased via eBay. The price was very reasonable. Testing with a HP ANA showed very low VSWR and the expected insertion loss up to 1 GHz. Shield resistance was very low, as expected. I have used these in lengths from 3 ft to 20 ft with no difficulty. The key here is the Belden part number in the vendors ad that can be checked to see what you are getting. The MIL SPEC and RG58 etc was stamped on the cables when received. For outstanding performance use RG-223 which is slightly larger than RG-58 and is a 50 Ohm cable having a very dense double sliver plated braid shield. You can buy these made up for a small fortune or buy an odd lot of RG-223 on eBay and make your own. Pasternak has the connectors with the appropriate diameter nuts and collars. The connectors for Rg-58 are had to make work on RG-223. Connectors for Type N and SMA are also available. Installing clamp style connectors on RG-223 requires a certain amount of passion (and a stainless steel welders tooth brush to comb the braid) but hey, no pain no gain. -73 john k6iql -Original Message- From: time-nuts-request time-nuts-requ...@febo.com To: time-nuts time-nuts@febo.com Sent: Sun, Mar 3, 2013 11:00 am Subject: time-nuts Digest, Vol 104, Issue 13 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Don't use cheap cables -- a cautionary tale (Bob Camp) 2. Re: webcam app to watch for and time stamp changes (Magnus Danielson) 3. Re: Don't use cheap cables -- a cautionary tale (John Ackermann) 4. Re: Don't use cheap cables -- a cautionary tale (Kevin Rosenberg) 5. Re: Don't use cheap cables -- a cautionary tale (Bob Camp) 6. Re: Don't use cheap cables -- a cautionary tale (Jim Lux) 7. Re: webcam app to watch for and time stamp changes (cfo) -- Message: 1 Date: Sun, 3 Mar 2013 10:10:38 -0500 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Message-ID: 335213bf-bbf3-44bd-9a7a-0bd481028...@rtty.us Content-Type: text/plain; charset=iso-8859-1 Hi By any chance is the connector a BNC? They have been known to create similar looking issues. Bob On Mar 3, 2013, at 9:59 AM, John Ackermann j...@febo.com wrote: I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds. I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot. The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem. Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. John austron-fts-beat-note.png___ 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. -- Message: 2 Date: Sun, 03 Mar 2013 16:29:15 +0100 From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] webcam app to watch for and time stamp changes Message-ID: 51336c4b.4030...@rubidium.dyndns.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Re: [time-nuts] Don't use cheap cables -- a cautionary tale
I use Ponoma cables that have the strain relief. However, I don't know about the cable construction itself. ___ 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] Don't use cheap cables -- a cautionary tale
Alligator clips, of course. -Bob On Sun, Mar 3, 2013 at 11:50 AM, Henk ten Pierick h...@deriesp.demon.nlwrote: Hi, The use of double shielded cables does raise the question to what type of connectors to use? Regards, Henk Op 3 mrt. 2013 om 17:30 heeft Jim Lux jim...@earthlink.net het volgende geschreven: On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
Some of the older synchronised signal generators (2-box systems) e.g Marconi, used TNC connectors with solid coax where signal leakage was likely to be a problem. Alan G3NYK - Original Message - From: Volker Esper ail...@t-online.de To: time-nuts@febo.com Sent: Sunday, March 03, 2013 6:49 PM Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Yes, we all have to learn that lesson... At the time I use bedea RG-223 and Belden H155 with soldered and crimped Telegaertner BNC connectors as general purpose cable (up to 2 GHz). Above that frequency I wouldn't use BNC. If you simply connect your tracking generator with the spectrum analyzer by using such a BNC cable there's not one that is absolutely stable when stressing the connector. I tried several manufacturers, HP, Suhner, Radiall, Rosenberger, it's always the same. To make precise measurements I prefer screwed connectors like N or SMA. Volker ___ 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] Don't use cheap cables -- a cautionary tale
I use some Pomonas also and I think they are single shielded except the Y which is double shielded. This may explain some artifacts I have in my house reference. Great Thread Thomas Knox To: time-nuts@febo.com From: johncr...@aol.com Date: Sun, 3 Mar 2013 14:08:15 -0500 Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale I could not agree more, having been burned once or twice. One batch of 50 Ohm cables was clearly marked 75 Ohms when received. These used some form of relatively high resistance foil shield and a drain wire for the outer conductor. The high resistance permitted a ground loop with hum on my 10 MHz reference thus FMing my signal generator. A couple of things to note: Measure the DC resistance between the connector bodies it should be way less than 1 Ohm, perhaps 0.1 ohm above what you see with the probes shorted. The previous regarding RG-58 apply unless the cable is labeled with a manufacturers part number and that is stated in the vendors spec - Such as BELDEN 8262 RG-58U Coaxial BNC M/M Patch Cable 10FT. RG58 C/U MIL C17 50 OHMS stamped on the cable. These were from - Digital Connections - cablesellforl...@yahoo.com and purchased via eBay. The price was very reasonable. Testing with a HP ANA showed very low VSWR and the expected insertion loss up to 1 GHz. Shield resistance was very low, as expected. I have used these in lengths from 3 ft to 20 ft with no difficulty. The key here is the Belden part number in the vendors ad that can be checked to see what you are getting. The MIL SPEC and RG58 etc was stamped on the cables when received. For outstanding performance use RG-223 which is slightly larger than RG-58 and is a 50 Ohm cable having a very dense double sliver plated braid shield. You can buy these made up for a small fortune or buy an odd lot of RG-223 on eBay and make your own. Pasternak has the connectors with the appropriate diameter nuts and collars. The connectors for Rg-58 are had to make work on RG-223. Connectors for Type N and SMA are also available. Installing clamp style connectors on RG-223 requires a certain amount of passion (and a stainless steel welders tooth brush to comb the braid) but hey, no pain no gain. -73 john k6iql -Original Message- From: time-nuts-request time-nuts-requ...@febo.com To: time-nuts time-nuts@febo.com Sent: Sun, Mar 3, 2013 11:00 am Subject: time-nuts Digest, Vol 104, Issue 13 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Don't use cheap cables -- a cautionary tale (Bob Camp) 2. Re: webcam app to watch for and time stamp changes (Magnus Danielson) 3. Re: Don't use cheap cables -- a cautionary tale (John Ackermann) 4. Re: Don't use cheap cables -- a cautionary tale (Kevin Rosenberg) 5. Re: Don't use cheap cables -- a cautionary tale (Bob Camp) 6. Re: Don't use cheap cables -- a cautionary tale (Jim Lux) 7. Re: webcam app to watch for and time stamp changes (cfo) -- Message: 1 Date: Sun, 3 Mar 2013 10:10:38 -0500 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Message-ID: 335213bf-bbf3-44bd-9a7a-0bd481028...@rtty.us Content-Type: text/plain; charset=iso-8859-1 Hi By any chance is the connector a BNC? They have been known to create similar looking issues. Bob On Mar 3, 2013, at 9:59 AM, John Ackermann j...@febo.com wrote: I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds. I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot. The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem. Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. John austron-fts-beat-note.png___ time-nuts mailing list -- time
Re: [time-nuts] Don't use cheap cables -- a cautionary tale
I do like the strain reliefs on the Pomona cables, but the cables themselves are leaky as expected. A couple of points: 1) If you don't have any other signal sources in your environment that are close to your measurement frequency but not coherent with it, you'll probably be OK with single-shielded cables. As soon as you bring that second oscillator into the room, though, you need to start thinking about the effects of cable leakage. Most people here have more than one oscillator in the house. :) For many types of measurements single shielded cables are not a big liability. Just be aware of the compromise you're making... and don't use them when debugging a sensitive phase comparator, let's put it that way. 2) Other than physical stability, I have never seen any problems that I could blame on a BNC connector that wasn't actually defective. The shield connection issues that Bob mentions are certainly valid concerns but they can happen with any fittings, not just BNC. There's no religious reason to avoid BNCs as long as you can keep everything still. And you shouldn't be moving cables around during measurements in any event. -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of li...@lazygranch.com Sent: Sunday, March 03, 2013 11:59 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale I use Ponoma cables that have the strain relief. However, I don't know about the cable construction itself. ___ 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] Don't use cheap cables -- a cautionary tale
I've previously encountered noise from mechanical movement of BNCs. You can definitely see noise bursts when you move a BNC cable around. Replacing TNC-BNC adapters and BNC-BNC cables at the analyzer with real TNC to SMA cables, and SMA to BNC adapters on the far end when necessary, solved a lot of those problems. But this was the first time I've seen a continuous beat-note type of interference that I could trace to the cabling. As a follow-on topic -- I wonder if the leakage problem would also be significant in a PPS distribution/measurement system (vs 5 or 10 MHz RF). I'd think that working with pulses and using a defined trigger level might mitigate that, but as I contemplate my rat's nest of PPS cabling I wonder if there could still be problems. John Alan Melia said the following on 03/03/2013 03:36 PM: Some of the older synchronised signal generators (2-box systems) e.g Marconi, used TNC connectors with solid coax where signal leakage was likely to be a problem. Alan G3NYK - Original Message - From: Volker Esper ail...@t-online.de To: time-nuts@febo.com Sent: Sunday, March 03, 2013 6:49 PM Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Yes, we all have to learn that lesson... At the time I use bedea RG-223 and Belden H155 with soldered and crimped Telegaertner BNC connectors as general purpose cable (up to 2 GHz). Above that frequency I wouldn't use BNC. If you simply connect your tracking generator with the spectrum analyzer by using such a BNC cable there's not one that is absolutely stable when stressing the connector. I tried several manufacturers, HP, Suhner, Radiall, Rosenberger, it's always the same. To make precise measurements I prefer screwed connectors like N or SMA. Volker ___ 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] Don't use cheap cables -- a cautionary tale
Fahnestock clips? -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert Darlington Sent: Sunday, March 03, 2013 11:04 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Alligator clips, of course. -Bob On Sun, Mar 3, 2013 at 11:50 AM, Henk ten Pierick h...@deriesp.demon.nlwrote: Hi, The use of double shielded cables does raise the question to what type of connectors to use? Regards, Henk Op 3 mrt. 2013 om 17:30 heeft Jim Lux jim...@earthlink.net het volgende geschreven: On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermann j...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
On 3/3/13 1:41 PM, DaveH wrote: Fahnestock clips? Alligator clips, of course. But, I looked through the connector catalogs and I didn't see any double shielded Fahnestock OR Alligator clips.. More seriously, you hook both shields to the shield of the connector. Unless you want to get Triax connectors or use Tip/Ring/Sleeve 1/4 or 1/8 phone plugs. They're used for shielded twisted pair kinds of applications as well (MIL-STD-1553B, for instance) and for audio applications. ___ 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] Don't use cheap cables -- a cautionary tale
RG-223 fits with Telegaertner J01000B0608 (Solder), Buerklin 78F201 or Rosenberger 51S107-108N4 (Crimp) (straight plugs BNC) H155 fits with Telegaertner T00100B3300 N Crimp) ... Am 03.03.2013 19:50, schrieb Henk ten Pierick: Hi, The use of double shielded cables does raise the question to what type of connectors to use? Regards, Henk Op 3 mrt. 2013 om 17:30 heeft Jim Luxjim...@earthlink.net het volgende geschreven: On 3/3/13 8:00 AM, Kevin Rosenberg wrote: On Mar 3, 2013, at 7:59 AM, John Ackermannj...@febo.com wrote: Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on. I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'. RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences). The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense. ___ 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] Don't use cheap cables -- a cautionary tale
After a couple of bad experiences with foamed polyethylene that got contaminated and solid polyethylene where heat had allowed the center conductor to shift, I have stuck with RG-142 and RG-400 style coax for short patch cables. For little stuff that gets soldered into place, I use add RG-316 and RG-178. Teflon makes all of these cables easy to solder without damage. On Sun, 3 Mar 2013 14:08:15 -0500 (EST), johncr...@aol.com wrote: I could not agree more, having been burned once or twice. One batch of 50 Ohm cables was clearly marked 75 Ohms when received. These used some form of relatively high resistance foil shield and a drain wire for the outer conductor. The high resistance permitted a ground loop with hum on my 10 MHz reference thus FMing my signal generator. A couple of things to note: Measure the DC resistance between the connector bodies it should be way less than 1 Ohm, perhaps 0.1 ohm above what you see with the probes shorted. The previous regarding RG-58 apply unless the cable is labeled with a manufacturers part number and that is stated in the vendors spec - Such as BELDEN 8262 RG-58U Coaxial BNC M/M Patch Cable 10FT. RG58 C/U MIL C17 50 OHMS stamped on the cable. These were from - Digital Connections - cablesellforl...@yahoo.com and purchased via eBay. The price was very reasonable. Testing with a HP ANA showed very low VSWR and the expected insertion loss up to 1 GHz. Shield resistance was very low, as expected. I have used these in lengths from 3 ft to 20 ft with no difficulty. The key here is the Belden part number in the vendors ad that can be checked to see what you are getting. The MIL SPEC and RG58 etc was stamped on the cables when received. For outstanding performance use RG-223 which is slightly larger than RG-58 and is a 50 Ohm cable having a very dense double sliver plated braid shield. You can buy these made up for a small fortune or buy an odd lot of RG-223 on eBay and make your own. Pasternak has the connectors with the appropriate diameter nuts and collars. The connectors for Rg-58 are had to make work on RG-223. Connectors for Type N and SMA are also available. Installing clamp style connectors on RG-223 requires a certain amount of passion (and a stainless steel welders tooth brush to comb the braid) but hey, no pain no gain. -73 john k6iql ___ 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] Don't use cheap cables -- a cautionary tale
Noise bursts come from the rubbing of the shield on the dielectric. Try putting some rg58 on the input of a guitar amp :-) Even low-noise rg58 type coax is noisy; it has some graphite on the dielectric supposedly to suppress the triboelectric (rubbing) noise. You might think Teflon would be quiet, but not so. Don John Ackermann I've previously encountered noise from mechanical movement of BNCs. You can definitely see noise bursts when you move a BNC cable around. Replacing TNC-BNC adapters and BNC-BNC cables at the analyzer with real TNC to SMA cables, and SMA to BNC adapters on the far end when necessary, solved a lot of those problems. But this was the first time I've seen a continuous beat-note type of interference that I could trace to the cabling. As a follow-on topic -- I wonder if the leakage problem would also be significant in a PPS distribution/measurement system (vs 5 or 10 MHz RF). I'd think that working with pulses and using a defined trigger level might mitigate that, but as I contemplate my rat's nest of PPS cabling I wonder if there could still be problems. John Alan Melia said the following on 03/03/2013 03:36 PM: Some of the older synchronised signal generators (2-box systems) e.g Marconi, used TNC connectors with solid coax where signal leakage was likely to be a problem. Alan G3NYK - Original Message - From: Volker Esper ail...@t-online.de To: time-nuts@febo.com Sent: Sunday, March 03, 2013 6:49 PM Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale Yes, we all have to learn that lesson... At the time I use bedea RG-223 and Belden H155 with soldered and crimped Telegaertner BNC connectors as general purpose cable (up to 2 GHz). Above that frequency I wouldn't use BNC. If you simply connect your tracking generator with the spectrum analyzer by using such a BNC cable there's not one that is absolutely stable when stressing the connector. I tried several manufacturers, HP, Suhner, Radiall, Rosenberger, it's always the same. To make precise measurements I prefer screwed connectors like N or SMA. Volker ___ 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] Don't use cheap cables -- a cautionary tale
This is a useful thread IMHO. Re the continuous beat note interference issue, I believe I've encountered this when evaluating a Datum1000B. At first I saw a periodic change in frequency of several E-10, the typical period was several hundred seconds. Turning off all the un needed gear in my lab except for a few ocxo's that i don't want to turn off and using double shielded RG400 cables without adapters for all the interconnections seemed to make the issue go away. All the outputs from the un used ocxo's were also terminated with bnc or sma terminators.Even the BNC T connectors I typically leave connected to the inputs of my HP5370B's (along with 50 ohm terminators) seemed to cause issues in this application. This issue has also prompted me to give up on my plans to move my GPSDO's from my radio room to my lab, as it's nice to be able to leave the GPSDO's running into a terminator vs having to shut them off. I've never really put much effort into tracking down the root cause of this issue but I suspect it is similar to what John mentioned. My FTS1050 (which IIRC is based on a datum 1000) doesn't seem to have this issue, building enclosures for my Datum1000's is on my post retirement to do list as I suspect running them without an enclosure may be contributing to this problem. As far as I know my BVA Ocxo is immune from this issue as well. Regards Mark Spencer Sent from my iPad ___ 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.
