Re: Topband: Mother of all ferrite common-mode coaxial chokes
Paul, I've used that installation method for at least 25 years, its easy to learn and it consistently produces excellent results. 73 Frank W3LPL Original message >Date: Fri, 13 Jul 2012 13:27:07 -0400 >From: "Paul Christensen" >Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >To: > >> "I've seen literally hundreds of improperly installed PL-259, type N and >> BNC >connectors." > >I agree for the most part, but in the case of using "UG" reducers with a >PL-259, I believe there's a better method over the "proper" procedure >supplied by Amphenol and the ARRL Handbook over the last several decades. > >http://www.w5fc.org/files/how-to/PL259.PDF > >It's a rare case, and in my initial review of the document, I was skeptical. >But after trying this method on several dozen RG-400 shack interconnect >cables, I'm convinced of the superiority of this method as it offers the >builder much greater quality control and work inspection. The builder is >not left to guess about what's happening inside the connector when using a >reducer. If the job isn't done right the first time, it's as easy as >spinning off the body and re-starting. That cannot be easily done with the >"proper" method since it requires soldering the UG adpter into the four >holes of the PL-259 connector body. Disassembly can be done, but with much >more work. Of course, another alternative is to use crimped connectors and >avoid the reducer, but I don't like their use outdoors or on cables subject >to repeated handling at the connector. > >Paul, W9AC > > > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 6:46 PM, Richard (Rick) Karlquist wrote: > Another thing you can do to measure chokes accurately is > to simply use a Vector Impedance Meter instead of a network > analyzer. Like the HP 4815A. In essence, it uses the VI > method, as the name implies. It doesn't care if the > impedance is nowhere near 50 ohms. For really high > impedances, it can be helpful to mathematically subtract > the stray capacitance of the probe. I've gotten excellent > results with my 4815 for years. That's exactly what's needed, and is the RF I-V method that both Wes and I cited. And yes, the capacitance of the test fixture can be a major source of error -- the equivalent circuit of a typical choke is parallel RLC, where R is typically on the order of 5K and C is on the order of 2-4 pF.. 73, Jim ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Another thing you can do to measure chokes accurately is to simply use a Vector Impedance Meter instead of a network analyzer. Like the HP 4815A. In essence, it uses the VI method, as the name implies. It doesn't care if the impedance is nowhere near 50 ohms. For really high impedances, it can be helpful to mathematically subtract the stray capacitance of the probe. I've gotten excellent results with my 4815 for years. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 6:21 PM, ZR wrote: > - Original Message - > From: "Jim Brown" > Cc: > Sent: Friday, July 13, 2012 4:37 PM > Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > >> On 7/13/2012 12:09 PM, ZR wrote: > > Thats correct at UHF and up but what is the error you have actually measured > at 1.8 MHz? The errors involved are NOT limited to UHF -- I've observed serious errors in the lower HF spectrum (i.e., below 10 MHz). It's why Chuck thinks the resonance of his chokes are as low as they are -- in reality, they resonate at a much higher frequency. And the errors are even greater with higher Q materials like #61. >> Quoting from Wes Hayward on the subject of measuring high impedances: >> > > > >From a quick glance thru that paper I dont see much benefit of RF I-V below > about 100MHz. What am I missing here? These are not simple issues. It takes far more than a quick glance -- you need to STUDY this stuff. I've provided some excellent references that are worthy of the effort. The issue is NOT the FREQUENCY of the measurement that causes the error, it is the fact that the magnitude of the impedance differs so much from 50 ohms. Wes is measuring at VHF, but I'm mostly measuring from 160M up to 10M. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Never mind, it was answered. Carl - Original Message - From: "ZR" To: "Paul Christensen" ; Sent: Friday, July 13, 2012 8:44 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > - Original Message - > From: "Paul Christensen" > To: > Sent: Friday, July 13, 2012 5:04 PM > Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > >>> One of the dumbest things I've seen recently from a very good company is >>> RF chokes in series with the shield connections on analog and RS232 I/O >>> boards for the Elecraft K3. >> >> Right. I think Joe, W4TV, was one of the first to identify that problem >> back around 2008. Many of us quickly jumpered the handful of RFCs used >> on >> shield leads of the RS232 I/O Board. Until revised by the factory, that >> board was the Achilles Heel of the K3. >> >>> Modern pro output stages have a very low source Z (typically >>> 100 ohms for line level) and high input Z (typically 10K for line >>> level), and consumer stuff is roughly 3-5X those values. >> >> Somewhere in my files from the late '80s is a white paper authored by >> Richard Cabot. I believe Richard was the chief designer of the Audio >> Precision brand of audio test equipment. The focus of the article was on >> the standarding of all audio output stages, balanced or unbalanced to a >> value of 40-50 ohms. He created models showing the effect of changing >> drive >> Z from 1-ohm through 600-ohms into long audio cables (and independent of >> terminating Z) that start to take on transmission line qualities. His >> conclusion was that a target of just under 50 ohms was optimum. >> >> Paul, W9AC >> > > What does he consider a long audio cable Paul? Ive been using 600 Ohms to > run studio type equipment for the AM station. > > Carl > KM1H > > >> ___ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> >> >> - >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 >> > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5130 - Release Date: 07/13/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
- Original Message - From: "Jim Brown" Cc: Sent: Friday, July 13, 2012 4:37 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > On 7/13/2012 12:09 PM, ZR wrote: >> ** Since when is using an established procedure called not knowing how >> to measure? > > When one does not understand (or take into account) the limitations of > the measurement method. The most common method of measuring Z at RF is > an S11 measurement in a 50 ohm system. This method has the limitation > that VERY small errors in the data, or VERY small calibration errors, > result in HUGE errors in the result when the unknown impedance differs > from the system impedance by more than about 5:1. The chokes he (and I) > were measuring have impedances on the order of 5,000 ohms, so an S11 > measurement will yield erroneous data. Thats correct at UHF and up but what is the error you have actually measured at 1.8 MHz? > > Quoting from Wes Hayward on the subject of measuring high impedances: > > "It is also possible to measure an L or a C attached as a load on a > bridge attached to the VNA. This is termed a "reflection" measurement. > The results are similar and remain equally difficult. The > severe errors of this direct method are discussed in Agilent > Applications note 1369-6.Much better measurements are obtained when > one uses a scheme called RF I-V where a radio frequency source is > applied to an unknown impedance. Then the current through the > impedance and the voltage across it are both measured. The vector > ratio of the values is calculated to obtain a better complex impedance > value. This method is discussed in Agilent Applications Note 1369-2. > N2PK has built his own version of the Agilent RF I-V scheme and > has obtained much better data. >From a quick glance thru that paper I dont see much benefit of RF I-V below about 100MHz. What am I missing here? > > Also see a brief discussion of RF-IV in > http://sdr-kits.net/DG8SAQ/VNWA/VNWA_HELP.pdf which is the manual for > the software for DG8SAQ's Vector Network Analyzer, and which supports > the N2PK RF-I-V fixture. > > 73, Jim K9YC > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
- Original Message - From: "Paul Christensen" To: Sent: Friday, July 13, 2012 5:04 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >> One of the dumbest things I've seen recently from a very good company is >> RF chokes in series with the shield connections on analog and RS232 I/O >> boards for the Elecraft K3. > > Right. I think Joe, W4TV, was one of the first to identify that problem > back around 2008. Many of us quickly jumpered the handful of RFCs used on > shield leads of the RS232 I/O Board. Until revised by the factory, that > board was the Achilles Heel of the K3. > >> Modern pro output stages have a very low source Z (typically >> 100 ohms for line level) and high input Z (typically 10K for line >> level), and consumer stuff is roughly 3-5X those values. > > Somewhere in my files from the late '80s is a white paper authored by > Richard Cabot. I believe Richard was the chief designer of the Audio > Precision brand of audio test equipment. The focus of the article was on > the standarding of all audio output stages, balanced or unbalanced to a > value of 40-50 ohms. He created models showing the effect of changing > drive > Z from 1-ohm through 600-ohms into long audio cables (and independent of > terminating Z) that start to take on transmission line qualities. His > conclusion was that a target of just under 50 ohms was optimum. > > Paul, W9AC > What does he consider a long audio cable Paul? Ive been using 600 Ohms to run studio type equipment for the AM station. Carl KM1H > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Ya think - Original Message - From: "David Raymond" To: Sent: Friday, July 13, 2012 6:48 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > This thread is beginning to wear thin. 73. . .Dave, W0FLS > - Original Message - > From: "Jim Brown" > To: > Sent: Friday, July 13, 2012 6:31 PM > Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > >> On 7/13/2012 2:04 PM, Paul Christensen wrote: One of the dumbest things I've seen recently from a very good company is RF chokes in series with the shield connections on analog and RS232 I/O boards for the Elecraft K3. >>> Right. I think Joe, W4TV, was one of the first to identify that problem >>> back around 2008. >> >> I think I was the first. Joe and I discussed the K3 a lot. >> Modern pro output stages have a very low source Z (typically 100 ohms for line level) and high input Z (typically 10K for line level), and consumer stuff is roughly 3-5X those values. >>> Somewhere in my files from the late '80s is a white paper authored by >>> Richard Cabot. I believe Richard was the chief designer of the Audio >>> Precision brand of audio test equipment. The focus of the article was >>> on >>> the standarding of all audio output stages, balanced or unbalanced to a >>> value of 40-50 ohms. He created models showing the effect of changing >>> drive >>> Z from 1-ohm through 600-ohms into long audio cables (and independent of >>> terminating Z) that start to take on transmission line qualities. His >>> conclusion was that a target of just under 50 ohms was optimum. >> >> Dick is a sharp guy. The best work I've seen on this topic was by the >> late Deane Jensen, c.a. 1980, showing that the capacitive loading of a >> long cable could make an output stage unstable, and that 100 ohms was a >> good value to prevent that from happening. That's been pretty much >> accepted as definitive, which is why most pro output stages are in that >> range. This can, of course, be device-dependent, and the lower value >> Dick suggested would be fine if the output device was unconditionally >> stable for all loads. It's VERY common in large installations for there >> to be 500-1,000 ft of cable bridging an output stage, and commonly used >> balanced audio cables range from as much as 40 pF/Ft (older stuff like >> Belden 8451) to as little as 13 pF/Ft for cable rated for AES3. >> >> That said, a cable would have to be VERY VERY VERY long to require >> transmission line analysis at audio frequencies, and applying >> transmission line analysis is VERY complex, because Zo varies over two >> orders of magnitude through the audio spectrum, converging to 75-100 >> ohms at HF for practical audio cables. See >> >> http://audiosystemsgroup.com/TransLines-LowFreq.pdf >> >> 73, Jim K9YC >> ___ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
wouldn't it be more fitting to say it has reached saturation ? :-) Bob K6UJ On Jul 13, 2012, at 4:48 PM, David Raymond wrote: > This thread is beginning to wear thin. 73. . .Dave, W0FLS > - Original Message - > From: "Jim Brown" > To: > Sent: Friday, July 13, 2012 6:31 PM > Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > >> On 7/13/2012 2:04 PM, Paul Christensen wrote: One of the dumbest things I've seen recently from a very good company is RF chokes in series with the shield connections on analog and RS232 I/O boards for the Elecraft K3. >>> Right. I think Joe, W4TV, was one of the first to identify that problem >>> back around 2008. >> >> I think I was the first. Joe and I discussed the K3 a lot. >> Modern pro output stages have a very low source Z (typically 100 ohms for line level) and high input Z (typically 10K for line level), and consumer stuff is roughly 3-5X those values. >>> Somewhere in my files from the late '80s is a white paper authored by >>> Richard Cabot. I believe Richard was the chief designer of the Audio >>> Precision brand of audio test equipment. The focus of the article was on >>> the standarding of all audio output stages, balanced or unbalanced to a >>> value of 40-50 ohms. He created models showing the effect of changing >>> drive >>> Z from 1-ohm through 600-ohms into long audio cables (and independent of >>> terminating Z) that start to take on transmission line qualities. His >>> conclusion was that a target of just under 50 ohms was optimum. >> >> Dick is a sharp guy. The best work I've seen on this topic was by the >> late Deane Jensen, c.a. 1980, showing that the capacitive loading of a >> long cable could make an output stage unstable, and that 100 ohms was a >> good value to prevent that from happening. That's been pretty much >> accepted as definitive, which is why most pro output stages are in that >> range. This can, of course, be device-dependent, and the lower value >> Dick suggested would be fine if the output device was unconditionally >> stable for all loads. It's VERY common in large installations for there >> to be 500-1,000 ft of cable bridging an output stage, and commonly used >> balanced audio cables range from as much as 40 pF/Ft (older stuff like >> Belden 8451) to as little as 13 pF/Ft for cable rated for AES3. >> >> That said, a cable would have to be VERY VERY VERY long to require >> transmission line analysis at audio frequencies, and applying >> transmission line analysis is VERY complex, because Zo varies over two >> orders of magnitude through the audio spectrum, converging to 75-100 >> ohms at HF for practical audio cables. See >> >> http://audiosystemsgroup.com/TransLines-LowFreq.pdf >> >> 73, Jim K9YC >> ___ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
This thread is beginning to wear thin. 73. . .Dave, W0FLS - Original Message - From: "Jim Brown" To: Sent: Friday, July 13, 2012 6:31 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > On 7/13/2012 2:04 PM, Paul Christensen wrote: >>> One of the dumbest things I've seen recently from a very good company is >>> RF chokes in series with the shield connections on analog and RS232 I/O >>> boards for the Elecraft K3. >> Right. I think Joe, W4TV, was one of the first to identify that problem >> back around 2008. > > I think I was the first. Joe and I discussed the K3 a lot. > >>> Modern pro output stages have a very low source Z (typically >>> 100 ohms for line level) and high input Z (typically 10K for line >>> level), and consumer stuff is roughly 3-5X those values. >> Somewhere in my files from the late '80s is a white paper authored by >> Richard Cabot. I believe Richard was the chief designer of the Audio >> Precision brand of audio test equipment. The focus of the article was on >> the standarding of all audio output stages, balanced or unbalanced to a >> value of 40-50 ohms. He created models showing the effect of changing >> drive >> Z from 1-ohm through 600-ohms into long audio cables (and independent of >> terminating Z) that start to take on transmission line qualities. His >> conclusion was that a target of just under 50 ohms was optimum. > > Dick is a sharp guy. The best work I've seen on this topic was by the > late Deane Jensen, c.a. 1980, showing that the capacitive loading of a > long cable could make an output stage unstable, and that 100 ohms was a > good value to prevent that from happening. That's been pretty much > accepted as definitive, which is why most pro output stages are in that > range. This can, of course, be device-dependent, and the lower value > Dick suggested would be fine if the output device was unconditionally > stable for all loads. It's VERY common in large installations for there > to be 500-1,000 ft of cable bridging an output stage, and commonly used > balanced audio cables range from as much as 40 pF/Ft (older stuff like > Belden 8451) to as little as 13 pF/Ft for cable rated for AES3. > > That said, a cable would have to be VERY VERY VERY long to require > transmission line analysis at audio frequencies, and applying > transmission line analysis is VERY complex, because Zo varies over two > orders of magnitude through the audio spectrum, converging to 75-100 > ohms at HF for practical audio cables. See > > http://audiosystemsgroup.com/TransLines-LowFreq.pdf > > 73, Jim K9YC > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 2:04 PM, Paul Christensen wrote: >> One of the dumbest things I've seen recently from a very good company is >> RF chokes in series with the shield connections on analog and RS232 I/O >> boards for the Elecraft K3. > Right. I think Joe, W4TV, was one of the first to identify that problem > back around 2008. I think I was the first. Joe and I discussed the K3 a lot. >> Modern pro output stages have a very low source Z (typically >> 100 ohms for line level) and high input Z (typically 10K for line >> level), and consumer stuff is roughly 3-5X those values. > Somewhere in my files from the late '80s is a white paper authored by > Richard Cabot. I believe Richard was the chief designer of the Audio > Precision brand of audio test equipment. The focus of the article was on > the standarding of all audio output stages, balanced or unbalanced to a > value of 40-50 ohms. He created models showing the effect of changing drive > Z from 1-ohm through 600-ohms into long audio cables (and independent of > terminating Z) that start to take on transmission line qualities. His > conclusion was that a target of just under 50 ohms was optimum. Dick is a sharp guy. The best work I've seen on this topic was by the late Deane Jensen, c.a. 1980, showing that the capacitive loading of a long cable could make an output stage unstable, and that 100 ohms was a good value to prevent that from happening. That's been pretty much accepted as definitive, which is why most pro output stages are in that range. This can, of course, be device-dependent, and the lower value Dick suggested would be fine if the output device was unconditionally stable for all loads. It's VERY common in large installations for there to be 500-1,000 ft of cable bridging an output stage, and commonly used balanced audio cables range from as much as 40 pF/Ft (older stuff like Belden 8451) to as little as 13 pF/Ft for cable rated for AES3. That said, a cable would have to be VERY VERY VERY long to require transmission line analysis at audio frequencies, and applying transmission line analysis is VERY complex, because Zo varies over two orders of magnitude through the audio spectrum, converging to 75-100 ohms at HF for practical audio cables. See http://audiosystemsgroup.com/TransLines-LowFreq.pdf 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> One of the dumbest things I've seen recently from a very good company is > RF chokes in series with the shield connections on analog and RS232 I/O > boards for the Elecraft K3. Right. I think Joe, W4TV, was one of the first to identify that problem back around 2008. Many of us quickly jumpered the handful of RFCs used on shield leads of the RS232 I/O Board. Until revised by the factory, that board was the Achilles Heel of the K3. > Modern pro output stages have a very low source Z (typically > 100 ohms for line level) and high input Z (typically 10K for line > level), and consumer stuff is roughly 3-5X those values. Somewhere in my files from the late '80s is a white paper authored by Richard Cabot. I believe Richard was the chief designer of the Audio Precision brand of audio test equipment. The focus of the article was on the standarding of all audio output stages, balanced or unbalanced to a value of 40-50 ohms. He created models showing the effect of changing drive Z from 1-ohm through 600-ohms into long audio cables (and independent of terminating Z) that start to take on transmission line qualities. His conclusion was that a target of just under 50 ohms was optimum. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
I agree with Tom on the F-connectors. I (now) have great results with the type-F connectors for my low band receive antennas. I was getting flaky connections with the connectors for some time and finally got a decent installation tool. Got a good F connector compression tool, for $55.00 (ouch) but now no problems. I watched a DirecTV guy one day using his compression tool and realized that is what I should use ! Bob K6UJ On Jul 13, 2012, at 1:08 PM, Tom W8JI wrote: >> I also use phono connectors on some older radios. I'd prefer to substitute >> BNC connectors but I don't want to modify the equipment. >> >> What I find helpful is to squeeze the shell of the plug so that it will >> fit tightly on the female receptacle and cover the shell with heat >> shrinkable tubing so that the pressure is always applied to the >> connection. > > That's exactly what I do periodically when the connectors lose tension. I > also use CM chokes (beads) near connectors in case they develop a little bit > of resistance. Overall, I have few problems. > > If you want a very reliable connector style for receiving, use a type-F > cable. Stay away from BNC's and other spring pressure connectors. Not only > is cable prep fast, and cable readily available, everything is dumbed down > to suit Larry-the-cable-guy. > > 73 Tom > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> One of the dumbest things I've seen recently from a very good company is > RF chokes in series with the shield connections on analog and RS232 I/O > boards for the Elecraft K3. Shielding and grounding is probably the least known art, as are audio line source and load impedances. I had problems with my K3 when I pointed my Yagi's at the house. As a quick fix, I cut into my mic cable and grounded the shield to a cabinet screw. :-) Later, I added some adhesive backed copper foil and got rid of the ground choke. Good thing about Elecraft is they fix bugs fast in production. ICOM ran an audio (mic) shield and a key paddle shield around inside the radio, instead of an entrance ground common point to the case. First time the negative lead comes off the 12V power supply or the negative fuse blows while a grounded case keyer is plugged in, and it melts the circuit board foil inside the radio. The same ICOM model in my shop lost the shield on the mic, because I lost a negative lead to the PS while a signal generator was connected. Turns out they had a small axial lead shield RF choke, and it opened up. The power supply negative returned through the safety ground on the generator to the mic shield. RF-wise, however, rigs are very good now. They are nonresponsive to RF ingress into the receiver on power and control jacks, and the output connectors are all very immune to generating CM RF on cable shields. My old boatanchors are often like open RF doors to the power mains. Some even bring so much RF out the front on knobs, they can pull the VFO off frequency! Things definitely are better. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 12:09 PM, ZR wrote: > ** Since when is using an established procedure called not knowing how > to measure? When one does not understand (or take into account) the limitations of the measurement method. The most common method of measuring Z at RF is an S11 measurement in a 50 ohm system. This method has the limitation that VERY small errors in the data, or VERY small calibration errors, result in HUGE errors in the result when the unknown impedance differs from the system impedance by more than about 5:1. The chokes he (and I) were measuring have impedances on the order of 5,000 ohms, so an S11 measurement will yield erroneous data. Quoting from Wes Hayward on the subject of measuring high impedances: "It is also possible to measure an L or a C attached as a load on a bridge attached to the VNA. This is termed a "reflection" measurement. The results are similar and remain equally difficult. The severe errors of this direct method are discussed in Agilent Applications note 1369-6.Much better measurements are obtained when one uses a scheme called RF I-V where a radio frequency source is applied to an unknown impedance. Then the current through the impedance and the voltage across it are both measured. The vector ratio of the values is calculated to obtain a better complex impedance value. This method is discussed in Agilent Applications Note 1369-2. N2PK has built his own version of the Agilent RF I-V scheme and has obtained much better data. Also see a brief discussion of RF-IV in http://sdr-kits.net/DG8SAQ/VNWA/VNWA_HELP.pdf which is the manual for the software for DG8SAQ's Vector Network Analyzer, and which supports the N2PK RF-I-V fixture. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Chokes, et. al.
I do not agree with that statement generally, especially when there is no good RF ground connection next to the rigs or the shack. If for instance you are using an antenna coupler with a doublet and open feeder then it is best to leave that floating and block common mode currents to the rig by a choke, if none is already part of the coupler and taking over that job. 73 Peter, DJ7WW -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Hal Kennedy Sent: Freitag, 13. Juli 2012 20:40 To: topband@contesting.com Subject: Topband: Chokes, et. al. Common mode chokes DO NOT belong between boxes on your desk. As Tom and others have said. The objective is to get them all at the same RF potential, not isolate them from one another so they can seek their own independent RF potential. 73 Hal N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 11:17 AM, Paul Christensen wrote: > It seems to me that any RF > current not contained within the inner conductor of the outer shield could > still divide across multiple paths as in the low frequency/DC context you > discussed. No? Exactly my point -- when the cable shield is improperly terminated, all bets are off, and we're left with the stupidity of the equipment designer/manufacturing engineer. But the errant currents are most likely to be RF currents, and they're going to be common mode on the shield. When a common mode choke is "solving" a problem, like noise or instability, the problem is with that shield connection, whether inside (Pin One) or outside (bad connector) the box. That's a major reason I don't like to go "inside the box" to correct Pin One Problems -- if the designer has managed to get the device stable with these design mistakes built in, I don't want to take a chance on upsetting the delicate balance between his various design mistakes and have to turn it into a science project to make it stable again. One of the dumbest things I've seen recently from a very good company is RF chokes in series with the shield connections on analog and RS232 I/O boards for the Elecraft K3. There were several other dumb things in those boards, some of which were corrected in later production. One was 500 ohms of series "build-out" resistors between the line level output stage and an unshielded output transformer under the misguided impression that 600 ohm output stages and input stages were a good thing. That approach was abandoned in the pro audio world nearly 50 years ago, because it degrades noise immunity and wastes 6 dB of headroom (or requires a line driver with 6dB greater output). Modern pro output stages have a very low source Z (typically 100 ohms for line level) and high input Z (typically 10K for line level), and consumer stuff is roughly 3-5X those values. More important, the series resistance removed the damping provided for the output transformers by the output stage, so the transformers produced high levels of distortion, even at very low output levels. And, because the transformers are unshielded, they are sitting ducks for any magnetic fields that may be around -- like leakage flux from the power supply for a power amp, which many hams locate either directly above or below the operating desk. My neighbor had a couple of the first K3s, and one of them got locked into a feedback loop at full output from that hum when he first tried to do AFSK. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> I also use phono connectors on some older radios. I'd prefer to substitute > BNC connectors but I don't want to modify the equipment. > > What I find helpful is to squeeze the shell of the plug so that it will > fit tightly on the female receptacle and cover the shell with heat > shrinkable tubing so that the pressure is always applied to the > connection. That's exactly what I do periodically when the connectors lose tension. I also use CM chokes (beads) near connectors in case they develop a little bit of resistance. Overall, I have few problems. If you want a very reliable connector style for receiving, use a type-F cable. Stay away from BNC's and other spring pressure connectors. Not only is cable prep fast, and cable readily available, everything is dumbed down to suit Larry-the-cable-guy. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> In my situation I have no control over RF grounding of the equipment since > the foundation is sitting in a hole blasted out of rock. Dirt all over the > property is only 1-2' on average. Grounding of equipment on the desk has nothing to do with TVI or RFI, unless you have terrible antenna common mode or other cable issues bringing RF into the shack, or cable or connector issues in the shack. If earth was important, satellites and airplanes would have huge radio problems. I think the myth that filters and equipment needs to be earthed comes from the false idea that filters divert unwanted signals to earth. Earthing is for low frequency and AC safety, unless you run a longwire from the desk tuner. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
- Original Message - From: "Jim Brown" To: Sent: Thursday, July 12, 2012 11:58 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > On 7/12/2012 5:48 PM, ZR wrote: >> Considering the YCCC's long time reputation for top level engineering >> ability plus the others mentioned such as K3LR Id consider that article a >> must read. > > The 2006 W1HIS piece gets many things very right but some things very > wrong. Tom has noted some things that are wrong. ** Which is strictly his opinion. Another is that Chuck > didn't understand the chokes he was recommending and trying to measure, > and he didn't know how to accurately measure them. ** Since when is using an established procedure called not knowing how to measure? He also didn't know > about the relatively new #31 material. ** Thats strange since he mentions the large 31 Mix beads a few times including their 3/2005 purchase date. He wasn't alone in any of that. > I got good measurements by measuring the chokes as the series element of > a voltage divider. Some guys working with the German VNWA have > implemented this in the software that supports it. Some guys working > with the N2PK VNA read the Agilient work on the IV method, and developed > a test fixture to implement it. All three of these methods can get good > data. > > I had been working on ferrite research for three years by the time I saw > Chuck's peice, and I corresponded with him about it. One MAJOR point he > got right is the importance of killing RX noise by killing common mode > current on the feedline, and it was one I hadn't thought of. I haven't > seen anything that Chuck published after this (six years ago), but I > consider my work much more advanced than his. ** Killing common mode for RX goes back long before 2006. I keep referring to the Tempest program and other screen room testing that goes back into the 70's and early 80's. Apparently you and Tom reinvented it decades later but since I was Tempest cleared/certified I and many others had been using it all along and there were no secrets about it eitherjust no Internet for instant distribution of knowledge. > > Some top level engineering does, in fact, occur outside New England. > Like in Georgia, and on the west coast. :) ** I agree, CA has a high percentage of the brain power in the US and GA has Georgia Tech and the companies that sprung up in the area by their engineering degreed graduates. There are 14 engineering schools in the state making GA well represented in various Engineering DEGREE programs. Carl KM1H > > 73, Jim K9YC > > . > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
In a message dated 7/12/2012 11:16:05 A.M. Eastern Daylight Time, tsho...@wmata.com writes: http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
donov...@starpower.net wrote: > Mike, > > I use BNC connectors extensively (almost exclusively) in the receive paths > in my station, perhaps one hundred or more. They have their own shield > integrity issues, there's no silver bullet with BNC connectors either. If > you ever encounter a BNC connector that mates "too easily" there may be a > Frank > W3LPL The "silver bullet" when it comes to BNC connectors is to instead use TNC connectors (same connector, only threaded not bayonet). In many cases, it is easy to retrofit BNC equipment with TNC. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Hi Mike, It was good to meet you for the first time this year in Dayton, I enjoyed our brief conversation in the flea market. I've had exactly the same experience with off brand BNC cables and connectors. I long ago placed them in the trash! When you get used to the normal mating tension in a good quality BNC connector, you will soon recognize bad ones. 73 Frank W3LPL Original message >Date: Fri, 13 Jul 2012 14:04:11 -0400 >From: "Mike Greenway" >Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >To: > >Just a note about something in this same vein that I ran into recently with >leakage in cables with BNC connectors. I bought some 3 ft jumpers made up >with BNC connectors and the connector has no tension when connecting to a >BNC jack and once in a while I have to reseat the connector to try and get >the connection back. How I noticed it was on a panadapter you could see >images start to ingress Also on a antenna connection I was getting some >hash from a switching supply in the receiver and reseating the BNC would >clear thing up. Amphenol and good quality BNC's have some resistance when >rotating the BNC ring and they are tight. The ones if have take very light >torque at all to rotate and hence they are not always making a solid >connection. They have no band marking so my guess is they are out of BY. >There is one major manufacturer using these right now but are soon to >replace them. 73 Mike K4PI > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Mike, I use BNC connectors extensively (almost exclusively) in the receive paths in my station, perhaps one hundred or more. They have their own shield integrity issues, there's no silver bullet with BNC connectors either. If you ever encounter a BNC connector that mates "too easily" there may be a shield integrity problem with the connector. Off brand BNC connectors are particularly problematic. 73 Frank W3LPL Original message >Date: Fri, 13 Jul 2012 17:31:24 + (UTC) >From: mstang...@comcast.net >Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >To: Tom W8JI >Cc: topband@contesting.com > >Tom and All, > >I also use phono connectors on some older radios. I'd prefer to substitute BNC >connectors but I don't want to modify the equipment. > >What I find helpful is to squeeze the shell of the plug so that it will fit >tightly on the female receptacle and cover the shell with heat shrinkable >tubing so that the pressure is always applied to the connection. > >Mike N2MS. > >- Original Message - >From: Tom W8JI >To: topband@contesting.com >Sent: Fri, 13 Jul 2012 16:08:18 - (UTC) >Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > > >Because I use phono plugs that really have improper shield grounding >integrity, and sometimes the pressure connections add a tiny bit of unwanted >shield impedance to the groundplane of "the box entrance", I use high >impedance beads on these particular cables. I also, as a practice, keep an >eye on those connectors. I use those connectors by necessity, because >several of my radios use phono plugs for external antenna ports, and there >is no easy way to change connectors. > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Chokes, et. al.
Common mode chokes DO NOT belong between boxes on your desk. As Tom and others have said. The objective is to get them all at the same RF potential, not isolate them from one another so they can seek their own independent RF potential. 73 Hal N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> NO, unless the coax shield is improperly terminated (the Pin One > Problem, or a badly installed connector). Makes sense to me, Jim except in the context of any RF current that could exist on the outside of the coaxial interconnect cable (e.g., between rig and amp) which when using the audio demonstration at 10 kHz or even 100 kHz may not show up well in current sensor tests. It seems to me that any RF current not contained within the inner conductor of the outer shield could still divide across multiple paths as in the low frequency/DC context you discussed. No? Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Just a note about something in this same vein that I ran into recently with leakage in cables with BNC connectors. I bought some 3 ft jumpers made up with BNC connectors and the connector has no tension when connecting to a BNC jack and once in a while I have to reseat the connector to try and get the connection back. How I noticed it was on a panadapter you could see images start to ingress Also on a antenna connection I was getting some hash from a switching supply in the receiver and reseating the BNC would clear thing up. Amphenol and good quality BNC's have some resistance when rotating the BNC ring and they are tight. The ones if have take very light torque at all to rotate and hence they are not always making a solid connection. They have no band marking so my guess is they are out of BY. There is one major manufacturer using these right now but are soon to replace them. 73 Mike K4PI ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Frank, I respect your input. In my situation I have no control over RF grounding of the equipment since the foundation is sitting in a hole blasted out of rock. Dirt all over the property is only 1-2' on average. The connectors are properly made and the cable was new Belden. The VSWR is not perfect at the high end of the 40-10M yagis which may contribute to some early TVI complaints and beads were used at all feed points.maybe not enough as all I had back then were the large 43 mix. I realize that in an ideal pure science world that Tom keeps rambling on about that beads in the shack arent required. OTOH for me they worked which is all Im really interested in. The TVI went completely away and allowed the station to compete in just about every major contest for 10 years or so without a telephone ringing once. Ive no idea if they are still needed with DTV, there are still a few stations on the lower VHF channels and not everyone is on Cable. If they help keep the locally radiated crud off the shield thats a bonus; it certainly works on the Beverages and Im relatively noise free on the TX antennas. Carl KM1H - Original Message - From: To: Sent: Friday, July 13, 2012 11:33 AM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > If ferrite isolators or beads have been determined to improve the shield > performance of a coaxial cable in your hamshack, something is > fundamentally wrong either with the cable (but most likely the connectors > at either end) or the shielded enclosure(s) its connected to. > > I've seen literally hundreds of improperly installed PL-259, type N and > BNC connectors. Years ago I stopped allowing anyone to bring coaxial > cables into my shack because so many are improperly installed. > > Outdoors the situation is fundamentally different, especially at the feed > point of a balanced antenna. Ferrites are a good choice for well designed > broadband baluns (but many popular baluns are poorly designed). For > monoband antennas I prefer 1/4 wavelength and 3/4 wavelength current > forcing coaxial cable baluns. See the latest ARRL Antenna Handbook, 22nd > edition, page 24-50, or > > http://www.qsl.net/i0jx/balun.pdf > > 73 > Frank > W3LPL > > > Original message >>Date: Fri, 13 Jul 2012 10:31:24 -0400 >>From: "Tom W8JI" >>Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >>To: >> >>Hi Carl, >> >>> Youre welcome to your opinion based upon your experience Tom. >> >>It is much more than experience. Good science can be proven or illustrated >>through experiments and measurements. Opinions are just opinions, and have >>the same value as the effort that went into confirming them. >> >>For example, a bead does not "keep a signal inside a cable". It simply >>changes the outside shield impedance. The outside of the shield, at a few >>hundred kilohertz or higher, is isolated by skin depth from what the >>filter >>affects. If we have significant or problematic outer shield currents on >>desk >>gear, it would be much better to fix the bad cable, bad connector, or >>figure >>out why the cabinet is behaving so poorly that unwanted currents spill >>over >>to the outside of the cable. >> >>There are valid applications for coaxial isolators, but they are all >>outside >>the shack or away from the desk equipment. >> >>> While 160 never presented any problems your rebuttal to the YCCC paper >>> was >>> generic and on 20-10 and also 6M I beg to differ based on my and others >>> experiences. >> >>Personal opinions, without reasonable technical backbone, don't mean much. >>Data, or at least good logical explanation of how something works, goes a >>whole lot further than opinions, guesses, or personal declarations. >> >>You can see how a wired connector disturbs common mode sensitivity here: >>http://www.w8ji.com/coaxial_cable_leakage.htm >> >>Scroll down to Connector Mounting and you will see just an inch of open >>connection to a non-chassis mounted connector on 8 feet of cable ( >>actually >>8' 3" with that pigtail installed) increased 40-meter common mode response >>by 40 dB over an 8-foot long cable routed normally. >> >>If I had common mode ingress or egress issues on higher power RF cables in >>my shack required illogical band-aids and hole plugs, I'd figure out what >>was really wrong with my equipment, cables, or wiring. :-)If stuff is >>built and wired correctly, there isn't even a reason to use RF grounds on >>a >>desk. They'll make no difference at all. Neither will isolators or beads >>on >>RF cables. >> >>73 Tom >> >>___ >>UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 > __
Re: Topband: Connector Integrity was: Re: Mother of all ferrite common-mode coaxial chokes
- Original Message - From: "Jim Brown" To: Sent: Friday, July 13, 2012 1:15 PM Subject: Re: Topband: Connector Integrity was: Re: Mother of all ferrite common-mode coaxial chokes > On 7/13/2012 9:46 AM, Pete Smith N4ZR wrote: >> Interesting point on phono plugs. I wonder if it would be useful to use >> one of the Caig Labs chemicals on those shells to enhance their contact >> with the jack. > > Better to buy and use proper connectors. Switchcraft makes EXCELLENT > phono and 3.5 mm plugs, and the lower cost plugs and jacks made by > Neutrik's Asian subsidiary are pretty good. I buy them from Full > Compass, a very good audio distributor in Madison, WI. Most folks with Drake, Collins, and some other vintage and pricey equipment arent about to do a Hammy Hambone conversion to better connectors. Carl KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 10:12 AM, Paul Christensen wrote: > What I think is missing from the discussion is that any benefit from using a > CM choke between shack hardware can be undermined by necessary parallel > paths. Consider a CM choke placed on the RF cable between a transmitter and > amplifier. Not only is the shield of the coaxial cable connected between > the equipment, but so is the AC ground conductor, and shielding of the PTT > key line and ALC line (if used). NO, unless the coax shield is improperly terminated (the Pin One Problem, or a badly installed connector). Remember -- a signal path through a transmission line looks to the source like a resistance equal to Zo, while ANY other return path includes the inductance of the loop, which is FAR greater than Zo. Thus, if we provide a proper transmission line path, there is ZERO RF current on those other conductors. ONLY at DC, or near DC, does any return current divide to those parallel paths. I witnessed an excellent demonstration of this at an IEEE EMC workshop many years ago when I was still living in Chicago. An audio generator fed RG58 with a load on the other end, and there was large buss bar running in parallel. There were current probes on both the buss bar and the shield. At very low audio frequencies (60 Hz, for example), all the current was in the buss bar -- it divided between the two paths by Ohm's Law, and the inductive reactance was near zero. At the shield cutoff frequency (roughly 1 kHz), the current began to shift to the cable shield, and by 10 kHz nearly all of the current was in the cable shield. Think about this in the context of band switching in a multi-band bandpass filter (like the ICE 419), or the RF path for T/R switching through a power amp. The GOOD ones don't depend on the chassis for signal return, it's an all coax path from input and output connectors through the switching relays. Ditto for antenna switching networks like those used to assign antennas in multi-transmitter stations. A properly built switching or relay box will either use coax or will have a proper ground plane carefully spaced so that return currents can follow a path directly under the "hot" path through the switch. Any inductance in that path is a common impedance that couples signal into other circuits (crosstalk). As Henry Ott has observed, we must always be aware of where the current is flowing, and that includes ALL of the current, and it includes the return path -- what he calls the invisible schematic hiding behind the "ground" symbol. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Tom and All, I also use phono connectors on some older radios. I'd prefer to substitute BNC connectors but I don't want to modify the equipment. What I find helpful is to squeeze the shell of the plug so that it will fit tightly on the female receptacle and cover the shell with heat shrinkable tubing so that the pressure is always applied to the connection. Mike N2MS. - Original Message - From: Tom W8JI To: topband@contesting.com Sent: Fri, 13 Jul 2012 16:08:18 - (UTC) Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes Because I use phono plugs that really have improper shield grounding integrity, and sometimes the pressure connections add a tiny bit of unwanted shield impedance to the groundplane of "the box entrance", I use high impedance beads on these particular cables. I also, as a practice, keep an eye on those connectors. I use those connectors by necessity, because several of my radios use phono plugs for external antenna ports, and there is no easy way to change connectors. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> "I've seen literally hundreds of improperly installed PL-259, type N and > BNC connectors." I agree for the most part, but in the case of using "UG" reducers with a PL-259, I believe there's a better method over the "proper" procedure supplied by Amphenol and the ARRL Handbook over the last several decades. http://www.w5fc.org/files/how-to/PL259.PDF It's a rare case, and in my initial review of the document, I was skeptical. But after trying this method on several dozen RG-400 shack interconnect cables, I'm convinced of the superiority of this method as it offers the builder much greater quality control and work inspection. The builder is not left to guess about what's happening inside the connector when using a reducer. If the job isn't done right the first time, it's as easy as spinning off the body and re-starting. That cannot be easily done with the "proper" method since it requires soldering the UG adpter into the four holes of the PL-259 connector body. Disassembly can be done, but with much more work. Of course, another alternative is to use crimped connectors and avoid the reducer, but I don't like their use outdoors or on cables subject to repeated handling at the connector. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Connector Integrity was: Re: Mother of all ferrite common-mode coaxial chokes
On 7/13/2012 9:46 AM, Pete Smith N4ZR wrote: > Interesting point on phono plugs. I wonder if it would be useful to use > one of the Caig Labs chemicals on those shells to enhance their contact > with the jack. Better to buy and use proper connectors. Switchcraft makes EXCELLENT phono and 3.5 mm plugs, and the lower cost plugs and jacks made by Neutrik's Asian subsidiary are pretty good. I buy them from Full Compass, a very good audio distributor in Madison, WI. But there's another more fundamental issue than the plug itself -- 99.9% of the time, the shell of the phono JACK built into the equipment doesn't go to the shielding enclosure, but instead goes to the "common" on the circuit board and wanders around for a while before it finds the chassis. This serious engineering mistake is a major cause of RFI. In the pro audio world, it's called "The Pin One Problem." And because it's a passive network, it both sends and receive RF trash. Now, it IS possible to terminate the cable shield to a properly implemented "ground layer" on a PC board, but as Henry Ott has observed both in his EMC seminars and in his classic text on EMC, any signal traces that cross a break in that layer can render it useless, putting RF trash on those external cables. Another point -- improper shield termination can also introduce instability in the circuit, because current doesn't flow where the designer hoped it would flow. Henry Ott's text is required reading. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> It seems Frank, Jim, myself, and many others are in exact agreement. This > is > because underlying science is universally logical and valid, and proven > both > by measurements and by time in thousands of commercial systems. What I think is missing from the discussion is that any benefit from using a CM choke between shack hardware can be undermined by necessary parallel paths. Consider a CM choke placed on the RF cable between a transmitter and amplifier. Not only is the shield of the coaxial cable connected between the equipment, but so is the AC ground conductor, and shielding of the PTT key line and ALC line (if used). But, the CM choke may still offer some benefit. I use a choke between my USB keyer and PC. The USB line sprays RFI/EMI without the choke. Yes, I could open up the equipment and look for Pin 1 problems. But I don't want to. If it's inside the PC, I want to leave it alone. Same for the keyer. It's probably the lazy way out, but with some equipment, I just don't want to make internal modifications. In those instances, I'm not opposed to trying a CM choke between shack hardware. If it works, great. If not, then I have the choice of living with the problem, making invasive modifications, or investigate some alternate cabling method. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Connector Integrity was: Re: Mother of all ferrite common-mode coaxial chokes
Interesting point on phono plugs. I wonder if it would be useful to use one of the Caig Labs chemicals on those shells to enhance their contact with the jack. They certainly work well on my Cinch-Jones plugs when they start to get flakey. 73, Pete N4ZR The World Contest Station Database, at www.conteststations.com The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and arcluster.reversebeacon.net, port 7000 On 7/13/2012 12:08 PM, Tom W8JI wrote: >> If ferrite isolators or beads have been determined to improve the shield >> performance of a coaxial cable in your hamshack, something is >> fundamentally wrong either with the cable (but most likely the connectors >> at either end) or the shielded enclosure(s) its connected to. >> >> I've seen literally hundreds of improperly installed PL-259, type N and >> BNC connectors. Years ago I stopped allowing anyone to bring coaxial >> cables into my shack because so many are improperly installed. > It seems Frank, Jim, myself, and many others are in exact agreement. This is > because underlying science is universally logical and valid, and proven both > by measurements and by time in thousands of commercial systems. > > Because I use phono plugs that really have improper shield grounding > integrity, and sometimes the pressure connections add a tiny bit of unwanted > shield impedance to the groundplane of "the box entrance", I use high > impedance beads on these particular cables. I also, as a practice, keep an > eye on those connectors. I use those connectors by necessity, because > several of my radios use phono plugs for external antenna ports, and there > is no easy way to change connectors. > > In some places, how we attach cables doesn't matter much at all. In other > places, in particular inside the hose, small errors can create large > problems. The building entrance is also critical, if we want to keep bad > things outside. > > Save the isolators for outside, where they might do something meaningful. > > 73 Tom > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
no flames, but it makes me embarrassed to say all i do is use extension cord material i buy at big lots and solder directly to the connectors. the wires break less than real coax and i can use my radio shack soldering iron... REAL coax (RG8) is only used between my 866s and the PA mike w7dra On Fri, 13 Jul 2012 12:32:26 -0400 Bill Cromwell writes: > Has anybody called the fire department? We have flames and smoke > rolling > out of here. > > 73, > > Bill KU8H > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > 53 Year Old Mom Looks 33 The Stunning Results of Her Wrinkle Trick Has Botox Doctors Worried http://thirdpartyoffers.juno.com/TGL3141/50004fbbef3d4fba4d9dst51vuc ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Has anybody called the fire department? We have flames and smoke rolling out of here. 73, Bill KU8H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
I've seen literally hundreds of improperly installed PL-259, type N and BNC connectors. Years ago I stopped allowing anyone to bring coaxial cables into my shack because so many are improperly installed. 73 Frank W3LPL Frank, I will agree with you. I can count one ONE hand the cables that I have seen that had the connectors installed correctly. It is not a lost art, it is stupidity! 73 Price W0RI - ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
> If ferrite isolators or beads have been determined to improve the shield > performance of a coaxial cable in your hamshack, something is > fundamentally wrong either with the cable (but most likely the connectors > at either end) or the shielded enclosure(s) its connected to. > > I've seen literally hundreds of improperly installed PL-259, type N and > BNC connectors. Years ago I stopped allowing anyone to bring coaxial > cables into my shack because so many are improperly installed. It seems Frank, Jim, myself, and many others are in exact agreement. This is because underlying science is universally logical and valid, and proven both by measurements and by time in thousands of commercial systems. Because I use phono plugs that really have improper shield grounding integrity, and sometimes the pressure connections add a tiny bit of unwanted shield impedance to the groundplane of "the box entrance", I use high impedance beads on these particular cables. I also, as a practice, keep an eye on those connectors. I use those connectors by necessity, because several of my radios use phono plugs for external antenna ports, and there is no easy way to change connectors. In some places, how we attach cables doesn't matter much at all. In other places, in particular inside the hose, small errors can create large problems. The building entrance is also critical, if we want to keep bad things outside. Save the isolators for outside, where they might do something meaningful. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
If ferrite isolators or beads have been determined to improve the shield performance of a coaxial cable in your hamshack, something is fundamentally wrong either with the cable (but most likely the connectors at either end) or the shielded enclosure(s) its connected to. I've seen literally hundreds of improperly installed PL-259, type N and BNC connectors. Years ago I stopped allowing anyone to bring coaxial cables into my shack because so many are improperly installed. Outdoors the situation is fundamentally different, especially at the feed point of a balanced antenna. Ferrites are a good choice for well designed broadband baluns (but many popular baluns are poorly designed). For monoband antennas I prefer 1/4 wavelength and 3/4 wavelength current forcing coaxial cable baluns. See the latest ARRL Antenna Handbook, 22nd edition, page 24-50, or http://www.qsl.net/i0jx/balun.pdf 73 Frank W3LPL Original message >Date: Fri, 13 Jul 2012 10:31:24 -0400 >From: "Tom W8JI" >Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes >To: > >Hi Carl, > >> Youre welcome to your opinion based upon your experience Tom. > >It is much more than experience. Good science can be proven or illustrated >through experiments and measurements. Opinions are just opinions, and have >the same value as the effort that went into confirming them. > >For example, a bead does not "keep a signal inside a cable". It simply >changes the outside shield impedance. The outside of the shield, at a few >hundred kilohertz or higher, is isolated by skin depth from what the filter >affects. If we have significant or problematic outer shield currents on desk >gear, it would be much better to fix the bad cable, bad connector, or figure >out why the cabinet is behaving so poorly that unwanted currents spill over >to the outside of the cable. > >There are valid applications for coaxial isolators, but they are all outside >the shack or away from the desk equipment. > >> While 160 never presented any problems your rebuttal to the YCCC paper was >> generic and on 20-10 and also 6M I beg to differ based on my and others >> experiences. > >Personal opinions, without reasonable technical backbone, don't mean much. >Data, or at least good logical explanation of how something works, goes a >whole lot further than opinions, guesses, or personal declarations. > >You can see how a wired connector disturbs common mode sensitivity here: >http://www.w8ji.com/coaxial_cable_leakage.htm > >Scroll down to Connector Mounting and you will see just an inch of open >connection to a non-chassis mounted connector on 8 feet of cable ( actually >8' 3" with that pigtail installed) increased 40-meter common mode response >by 40 dB over an 8-foot long cable routed normally. > >If I had common mode ingress or egress issues on higher power RF cables in >my shack required illogical band-aids and hole plugs, I'd figure out what >was really wrong with my equipment, cables, or wiring. :-)If stuff is >built and wired correctly, there isn't even a reason to use RF grounds on a >desk. They'll make no difference at all. Neither will isolators or beads on >RF cables. > >73 Tom > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Hi Carl, > Youre welcome to your opinion based upon your experience Tom. It is much more than experience. Good science can be proven or illustrated through experiments and measurements. Opinions are just opinions, and have the same value as the effort that went into confirming them. For example, a bead does not "keep a signal inside a cable". It simply changes the outside shield impedance. The outside of the shield, at a few hundred kilohertz or higher, is isolated by skin depth from what the filter affects. If we have significant or problematic outer shield currents on desk gear, it would be much better to fix the bad cable, bad connector, or figure out why the cabinet is behaving so poorly that unwanted currents spill over to the outside of the cable. There are valid applications for coaxial isolators, but they are all outside the shack or away from the desk equipment. > While 160 never presented any problems your rebuttal to the YCCC paper was > generic and on 20-10 and also 6M I beg to differ based on my and others > experiences. Personal opinions, without reasonable technical backbone, don't mean much. Data, or at least good logical explanation of how something works, goes a whole lot further than opinions, guesses, or personal declarations. You can see how a wired connector disturbs common mode sensitivity here: http://www.w8ji.com/coaxial_cable_leakage.htm Scroll down to Connector Mounting and you will see just an inch of open connection to a non-chassis mounted connector on 8 feet of cable ( actually 8' 3" with that pigtail installed) increased 40-meter common mode response by 40 dB over an 8-foot long cable routed normally. If I had common mode ingress or egress issues on higher power RF cables in my shack required illogical band-aids and hole plugs, I'd figure out what was really wrong with my equipment, cables, or wiring. :-)If stuff is built and wired correctly, there isn't even a reason to use RF grounds on a desk. They'll make no difference at all. Neither will isolators or beads on RF cables. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Youre welcome to your opinion based upon your experience Tom. While 160 never presented any problems your rebuttal to the YCCC paper was generic and on 20-10 and also 6M I beg to differ based on my and others experiences. Carl KM1H - Original Message - From: "Tom W8JI" To: Sent: Thursday, July 12, 2012 9:58 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > Carl, > > Regardless of what feelings people might have, beads and isolators really > do > not belong on transmitter lines between amplifiers and radios, or between > filters and amplifiers. > > There isn't any reasonable logical technical reason for using them there, > and there are many reasons not to use them. > > I can't think of a bigger waste of time and ferrite materials. > > 73 Tom > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Hi Victor, > Using them a lot between VHF and UHF boxes to break ground RF paths. Beads and common mode chokes only modify common mode impedance on the outside of cable shield. They do this by allowing a voltage difference to appear across the bead or choke. This means the cable shield going in floats at a different RF potential than the cable shield exiting. It is almost never a good thing to have potential differences across cable shields on a desk full of lower-level lines. If any of us have bothersome or significant RF currents in our shacks on the outside of cables, we really should learn why the RF is there and fix the real problem. The last thing we should be doing is floating ground connections (which is what the outside of the shield provides) between different equipment on a desk. The most we can expect from isolating the outer shield path is moving equalizing currents to other cables and wires between gear. Beads over transmitting cables between major equipment just isn't a good idea at all as a general practice. > Really helps to prevents all kinds of unpredictable oscillation effects. If the equipment system changes by moving wires around, or changing the impedance of the shield outside, there must be a problem with connector mounting and shield impedance, or poor cabinet design. As for equipment, there are a few cases of terrible cabinets. At least one commercial antenna tuner has an intentionally insulated cover, and another tuner uses a single core 4:1 current balun that forces output lines into significant voltage unbalance. No one can dispute there are occasional serious errors in equipment design. The correction for those and other errors is not in grounding connections to a ground buss, or isolators, or strings of beads. The fix is correcting the defect in the gear. Otherwise, when we throw an isolator or beads on cables, we simply move the problem someplace else in the wiring where it waits to cause problems in the future. Isolators have a place in the world of antennas and feedlines outside the ham shack. They can be important when a system is neither perfectly balanced nor perfectly unbalanced. Marconi verticals with less than perfect grounds are examples of systems operating in the netherworld between perfectly unbalanced and perfectly balanced. But in cases like that, we want the isolation that allows voltages to be different along a section of coaxial cable OUTSIDE the house, not inside the house where noise and devices sensitive to RF live. Inside the house, we really want all cabinets and device chassis to have the same RF potential. We do not want to isolate cabinets from each other, allowing them to float to different potentials to ground. If throwing beads or isolators on an RF line inside the shack changes something, that line has a problem that needs fixed or at least needs understood. The only beads in my shacks on any RF cables are on receiver leads that have phono plugs, because the layout of the plugs and the shield connections are less than ideal. I live with those connections because that is the type of connector used. I understand what the problem is and choose to work around it, and I keep an eye on it. I can't imagine having connections like that on a 100-watt transmitting line, let alone 1500 watts. Transmitters deserve real connectors mounted properly, and cabinets with RF integrity at joints. This is all measureable and rationally explainable. It isn't voodoo science, like stringing beads everywhere to "make signals stay inside cables". Beads don't make anything stay inside something, they allow a larger longitudinal voltage difference to occur along a small length of conductor. We want that between radials and a coax feedline shield outside the house, but why would we intentionally want two shield ends of a shielded RF cable between two cabinets to have greater potential difference on our desks? We really should never want shields to be that way, if we have any choice at all. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Mother of all ferrite common-mode coaxial chokes
Using them a lot between VHF and UHF boxes to break ground RF paths. Really helps to prevens all kinds of unpredictable oscillation effects. Planning to be on 160 this coming season to finish Tob Band DXCC required for field checking. In the mean time studying necessary technical references. On Fri, 13 Jul 2012 01:58:46 -, Tom W8JI wrote: > Carl, > > Regardless of what feelings people might have, beads and isolators > really do > not belong on transmitter lines between amplifiers and radios, or between > filters and amplifiers. > > There isn't any reasonable logical technical reason for using them there, > and there are many reasons not to use them. > > I can't think of a bigger waste of time and ferrite materials. > > 73 Tom > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > -- 73 Vic US5WE/K1WE (UW5W in VHF contests) KN29AU UARL VHF committee Chairman, UARL Lvov Branch "LKK" Moderator, UARL VHF portal http://www.vhfdx.at.ua DXCC card checker in Ukraine - Zorg: If you want something done, do it yourself. Yep! ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
