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MFJ-269 Antenna Analyzer experience
Hi all
I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. -- Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
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Hash: SHA1 Peter wrote: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. A good place to check for reviews is at eham.net. http://www.eham.net/reviews/ http://www.eham.net/reviews/detail/803 - -- Best Regards, Keith http://home.comcast.net/~kilowattradio/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Darwin) iEYEARECAAYFAkqHgxkACgkQgvlh1smTcVUcpwCgmFxYEYBk+k ymOW1QRNXMcL49 AMUAoM72LohuNcyx/PMVC2oFFq5sZ52Y =MH3C -----END PGP SIGNATURE----- |
MFJ-269 Antenna Analyzer experience
Peter wrote:
Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. I have one and find it extremely handy for a variety of tasks such as measuring the length or velocity factor of coax lines or the impedance of ferrite cores. But ironically, the one thing it's almost completely useless for, at my QTH, is analyzing antennas. Induced fields from TV, FM, and AM broadcast stations are so high that the MFJ isn't able to detect its own signal. This isn't unique to the MFJ -- I've had the same problem with a very expensive HP digital impedance meter, and revert to my old GR bridge with a tuned receiver for a detector when I want to actually measure an antenna's impedance. For me the MFJ is worthwhile just for the other functions it provides, but it might or might not be for you. Just keep in mind that, depending on your QTH, it might not be able to actually measure antenna impedances. Roy Lewallen, W7EL |
MFJ-269 Antenna Analyzer experience
"Roy Lewallen" wrote in message ... Peter wrote: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. I have one and find it extremely handy for a variety of tasks such as measuring the length or velocity factor of coax lines or the impedance of ferrite cores. But ironically, the one thing it's almost completely useless for, at my QTH, is analyzing antennas. Induced fields from TV, FM, and AM broadcast stations are so high that the MFJ isn't able to detect its own signal. This isn't unique to the MFJ -- I've had the same problem with a very expensive HP digital impedance meter, and revert to my old GR bridge with a tuned receiver for a detector when I want to actually measure an antenna's impedance. For me the MFJ is worthwhile just for the other functions it provides, but it might or might not be for you. Just keep in mind that, depending on your QTH, it might not be able to actually measure antenna impedances. Roy Lewallen, W7EL Roy All comments noted. I do in fact live within 2km of an AM transmitter although I believe it's not that high powered and I also have an FM transmitter within 5km, therefore I'm interested in the details of your location in relation to the various transmitters. Regards -- Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
"Keith" wrote in message ... -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Peter wrote: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. A good place to check for reviews is at eham.net. http://www.eham.net/reviews/ http://www.eham.net/reviews/detail/803 - -- Best Regards, Keith http://home.comcast.net/~kilowattradio/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Darwin) Thanks for the links Keith Regards -- Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
On Sat, 15 Aug 2009 22:47:05 -0700, Roy Lewallen
wrote: Peter wrote: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. I have one and find it extremely handy for a variety of tasks such as measuring the length or velocity factor of coax lines or the impedance of ferrite cores. But ironically, the one thing it's almost completely useless for, at my QTH, is analyzing antennas. Induced fields from TV, FM, and AM broadcast stations are so high that the MFJ isn't able to detect its own signal. This isn't unique to the MFJ -- I've had the same problem with a very expensive HP digital impedance meter, and revert to my old GR bridge with a tuned receiver for a detector when I want to actually measure an antenna's impedance. For me the MFJ is worthwhile just for the other functions it provides, but it might or might not be for you. Just keep in mind that, depending on your QTH, it might not be able to actually measure antenna impedances. Roy Lewallen, W7EL I live in a very rural area and mine works as advertised. I don't use it very much because it gives quick and complete answers. |
MFJ-269 Antenna Analyzer experience
"Peter" wrote in
. au: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Peter, Effective exploitation of the capability of this type of analyser depends on a sound understanding of transmission lines, and of the instrument's own limitation. The availability of these analysers at low cost, and the perception that they are a magic bullet has lead to a lot of pseudo technical nonsense being proposed. The magic is more in the user's capability than the box, and buying the box doesn't buy knowledge and understanding... but the device can help develop knowledge and understanding. I have not used a '269 (though I have extensively used a '259B), but I suspect that it does not display the sign of X. Estimation of the sign of X in the '259 and similar instruments is an issue, and confuses many users. There are propositions that sign of X is easily determined from the slope of X with frequency at a point... but whilst that is true for an ideal passive component, it is not true in general. These instruments are often used in pursuit of the questionable goal of resonance, and the instrument used to show resonance by observing X=0, or X approximately zero, or a local minimum for X at some frequency on the assumption that X changes sign at that point and that resonance of something is indicated. I wrote some notes entitled "In pursuit of dipole resonance with an MFJ259B" at http://vk1od.net/blog/?p=680 that canvasses the behaviour of the instrument in such an application, and flags the issues in measurement. You may find them interesting. Others have raised the issue that these instruments use a broadband detector, which works fine so long as the internal oscillator has low harmonic content and dominates the detector. If you let one of these things time out, the oscillator is shut down, and if you see indication on the meters, then energy from another source is of sufficient magnitude to be concerned about the accuracy of measurements. Owen |
MFJ-269 Antenna Analyzer experience
Peter wrote:
Roy All comments noted. I do in fact live within 2km of an AM transmitter although I believe it's not that high powered and I also have an FM transmitter within 5km, therefore I'm interested in the details of your location in relation to the various transmitters. Regards Roughly 10 - 15 miles from here is a ridge about 800 feet higher than my location. On top are virtually all the TV and FM, and a number of the AM, transmitters for the Portland Oregon metropolitan area. A single strong transmitter is likely to be enough to confuse an antenna analyzer, though. Filtering is possible, of course, but you have to take care to design filters to have minimal effect on measured impedances while still filtering effectively. This can sometimes be challenging depending on the strength of the interfering signal and how far it is from the measurement frequency. I also have to be careful when working on audio circuitry -- on several occasions I've tracked down "hum" as demodulated TV video, and I end up having to include VHF decoupling and shielding to audio circuits. Don't know much about the nature of HDTV signals, but it might not be so bad if it doesn't have as much energy in the AF range when demodulated. It's bound to drive untuned antenna analyzers bonkers, though. Roy Lewallen, W7EL |
MFJ-269 Antenna Analyzer experience
"Peter" wrote in message . au... Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Hi Peter, I can highly recommend the Rigexpert AA-200A: http://www.rigexpert.com/index?s=aa200 Unlike the MFJ unit, this is a full vector analyzer. You can also save plots and then transfer them to your computer for archiving. The lates firmware allows measurements at both 50 Ohms and 75 Ohms and I believe one can now also move the reference plane to the end of the coax. Batteries last forever, it's about 1/4th the weight, can display data in both graphical and tabular format. I've owned the MFJ, Autek, AEA and Timewave- the AA-200A blows them all away. Oh yeah, the signal source is synthesized and can make a very nice signal generator that is rock stable. Dale W4OP |
MFJ-269 Antenna Analyzer experience
Dale Parfitt wrote:
"Peter" wrote in message . au... Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Hi Peter, I can highly recommend the Rigexpert AA-200A: http://www.rigexpert.com/index?s=aa200 Unlike the MFJ unit, this is a full vector analyzer. You can also save plots and then transfer them to your computer for archiving. The lates firmware allows measurements at both 50 Ohms and 75 Ohms and I believe one can now also move the reference plane to the end of the coax. Batteries last forever, it's about 1/4th the weight, can display data in both graphical and tabular format. I've owned the MFJ, Autek, AEA and Timewave- the AA-200A blows them all away. Oh yeah, the signal source is synthesized and can make a very nice signal generator that is rock stable. Dale W4OP Except that it looks like the RigExpert has an untuned detector, just like the others. The schematic SUBVHF6.pdf shows a couple of RF switches and a AD8307 log detector. The PLL synthesizers are up at 1+ GHz, so maybe there's a filter and mixer somewhere else. I couldn't find a block diagram. |
MFJ-269 Antenna Analyzer experience
I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Hi Peter, I can highly recommend the Rigexpert AA-200A: http://www.rigexpert.com/index?s=aa200 Unlike the MFJ unit, this is a full vector analyzer. You can also save plots and then transfer them to your computer for archiving. The lates firmware allows measurements at both 50 Ohms and 75 Ohms and I believe one can now also move the reference plane to the end of the coax. Batteries last forever, it's about 1/4th the weight, can display data in both graphical and tabular format. I've owned the MFJ, Autek, AEA and Timewave- the AA-200A blows them all away. Oh yeah, the signal source is synthesized and can make a very nice signal generator that is rock stable. Dale W4OP Except that it looks like the RigExpert has an untuned detector, just like the others. The schematic SUBVHF6.pdf shows a couple of RF switches and a AD8307 log detector. The PLL synthesizers are up at 1+ GHz, so maybe there's a filter and mixer somewhere else. I couldn't find a block diagram. Hi Jim, I'm way up in the NC mountains, so I cannot speak regarding the AA-200A front end. I know when I lived in West Palm FL, the MFJ was totally wiped out by a nearby AM broadcast station. 73, Dale W4OP |
MFJ-269 Antenna Analyzer experience
Dale Parfitt wrote:
I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Hi Peter, I can highly recommend the Rigexpert AA-200A: http://www.rigexpert.com/index?s=aa200 Unlike the MFJ unit, this is a full vector analyzer. You can also save plots and then transfer them to your computer for archiving. The lates firmware allows measurements at both 50 Ohms and 75 Ohms and I believe one can now also move the reference plane to the end of the coax. Batteries last forever, it's about 1/4th the weight, can display data in both graphical and tabular format. I've owned the MFJ, Autek, AEA and Timewave- the AA-200A blows them all away. Oh yeah, the signal source is synthesized and can make a very nice signal generator that is rock stable. Dale W4OP Except that it looks like the RigExpert has an untuned detector, just like the others. The schematic SUBVHF6.pdf shows a couple of RF switches and a AD8307 log detector. The PLL synthesizers are up at 1+ GHz, so maybe there's a filter and mixer somewhere else. I couldn't find a block diagram. Hi Jim, I'm way up in the NC mountains, so I cannot speak regarding the AA-200A front end. I know when I lived in West Palm FL, the MFJ was totally wiped out by a nearby AM broadcast station. Yah, on the low bands I sometimes have problems with a local AM station. It's probably endemic to most analyzers. My thoughts on the MFJ line of analyzers is that within their limitations, they are very good. I bought one and it just works fine for me. The original one I bought had a problem at around 10-11 months. I think that someone was messing with it in a high RF environment without the dummy load on the RF connector. Somehow got a major dose of RF. Sent it back to MFJ,and the replacement works just great. I don't loan it out any more. My biggest con is that it uses a lot of AA cells, no big deal. I'd buy another one in a minute if needed. My new loaner is an older MFJ SWR bridge - since that is what most people are worried about anyhow. - 73 de Mike N3LI - |
MFJ-269 Antenna Analyzer experience
Michael Coslo wrote:
My biggest con is that it uses a lot of AA cells, ... I solved that problem with a Velcro'ed gel cell. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
MFJ-269 Antenna Analyzer experience
My biggest con is that it uses a lot of AA cells, ...
I solved that problem with a Velcro'ed gel cell. I don't know about the '269, but the '259 practically GOBBLED batteries! I currently use an Autek VA-1 and have been reasonably happy with it. --Myron A. Calhoun, W0PBV. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge |
MFJ-269 Antenna Analyzer experience
"Owen Duffy" wrote in message ... "Peter" wrote in . au: Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. Peter, Effective exploitation of the capability of this type of analyser depends on a sound understanding of transmission lines, and of the instrument's own limitation. The availability of these analysers at low cost, and the perception that they are a magic bullet has lead to a lot of pseudo technical nonsense being proposed. The magic is more in the user's capability than the box, and buying the box doesn't buy knowledge and understanding... but the device can help develop knowledge and understanding. I have not used a '269 (though I have extensively used a '259B), but I suspect that it does not display the sign of X. Estimation of the sign of X in the '259 and similar instruments is an issue, and confuses many users. There are propositions that sign of X is easily determined from the slope of X with frequency at a point... but whilst that is true for an ideal passive component, it is not true in general. These instruments are often used in pursuit of the questionable goal of resonance, and the instrument used to show resonance by observing X=0, or X approximately zero, or a local minimum for X at some frequency on the assumption that X changes sign at that point and that resonance of something is indicated. I wrote some notes entitled "In pursuit of dipole resonance with an MFJ259B" at http://vk1od.net/blog/?p=680 that canvasses the behaviour of the instrument in such an application, and flags the issues in measurement. You may find them interesting. Others have raised the issue that these instruments use a broadband detector, which works fine so long as the internal oscillator has low harmonic content and dominates the detector. If you let one of these things time out, the oscillator is shut down, and if you see indication on the meters, then energy from another source is of sufficient magnitude to be concerned about the accuracy of measurements. Owen Thanks Owen for the information and your notes "In pursuit of dipole resonance with an MFJ259B" My intended use for the device is to get a bit of view on what's going on with my various home brew antennas and matching devices and for my own curiosity to compare theory with real world. I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Regards Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
"Peter" wrote in
. au: .... I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Ah, you were looking for honesty in advertising! The online guff on the MFJ259B says: "Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees)." The MFJ259B definitely does *not* show phase angle or reactance as negative for cases where X is actually negative. The same words appear in the MFJ269 online page, so it may also be a misrepresentation. I see in the MFJ269 manual, the same pretence over the sign of phase and reactance. It contains the words "Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase difference between current and voltage at the terminals of the analyzer." Of course, a phase angle between "zero and 90 degrees" does not represent "phase difference between current and voltage at the terminals of the analyzer" in the case of a capacitive impedance. Honesty in advertising... think again. Owen |
MFJ-269 Antenna Analyzer experience
"Owen Duffy" wrote in message ... "Peter" wrote in . au: ... I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Ah, you were looking for honesty in advertising! The online guff on the MFJ259B says: "Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees)." The MFJ259B definitely does *not* show phase angle or reactance as negative for cases where X is actually negative. The same words appear in the MFJ269 online page, so it may also be a misrepresentation. I see in the MFJ269 manual, the same pretence over the sign of phase and reactance. It contains the words "Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase difference between current and voltage at the terminals of the analyzer." Of course, a phase angle between "zero and 90 degrees" does not represent "phase difference between current and voltage at the terminals of the analyzer" in the case of a capacitive impedance. Honesty in advertising... think again. Owen What was I thinking! I was impressed with what was being claimed. I will continue with my product research and you can expect me to float some other manufactures device on this group soon for comments. Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
"Peter" wrote in message ... "Owen Duffy" wrote in message ... "Peter" wrote in . au: ... I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Ah, you were looking for honesty in advertising! The online guff on the MFJ259B says: "Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees)." The MFJ259B definitely does *not* show phase angle or reactance as negative for cases where X is actually negative. The same words appear in the MFJ269 online page, so it may also be a misrepresentation. I see in the MFJ269 manual, the same pretence over the sign of phase and reactance. It contains the words "Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase difference between current and voltage at the terminals of the analyzer." Of course, a phase angle between "zero and 90 degrees" does not represent "phase difference between current and voltage at the terminals of the analyzer" in the case of a capacitive impedance. Honesty in advertising... think again. Owen What was I thinking! I was impressed with what was being claimed. I will continue with my product research and you can expect me to float some other manufactures device on this group soon for comments. Peter VK6YSF Again- look at the RigExpert A-200A. Batteries seem to last forever, it's USB upgradable and it DOES resolve the sign of R +/-JX. Dale W4OP |
MFJ-269 Antenna Analyzer experience
"Dale Parfitt" wrote in message ... "Peter" wrote in message ... "Owen Duffy" wrote in message ... "Peter" wrote in . au: ... I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Ah, you were looking for honesty in advertising! The online guff on the MFJ259B says: "Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees)." The MFJ259B definitely does *not* show phase angle or reactance as negative for cases where X is actually negative. The same words appear in the MFJ269 online page, so it may also be a misrepresentation. I see in the MFJ269 manual, the same pretence over the sign of phase and reactance. It contains the words "Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase difference between current and voltage at the terminals of the analyzer." Of course, a phase angle between "zero and 90 degrees" does not represent "phase difference between current and voltage at the terminals of the analyzer" in the case of a capacitive impedance. Honesty in advertising... think again. Owen What was I thinking! I was impressed with what was being claimed. I will continue with my product research and you can expect me to float some other manufactures device on this group soon for comments. Peter VK6YSF Again- look at the RigExpert A-200A. Batteries seem to last forever, it's USB upgradable and it DOES resolve the sign of R +/-JX. Dale W4OP Thanks Dale I have just had a look at the RigExpert site. Look impressive, but the MFJ269 at about $400US was about my limit. I think I will take a step back and conduct a more scientific review of all of the antenna analyzers on offer, there for you should get sick of my postings over the next couple of weeks/months. I must say that the ability to save and analyze data on the lap top is an appealing feature. Regards Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
Peter wrote:
I have just had a look at the RigExpert site. Look impressive, but the MFJ269 at about $400US was about my limit. I think I will take a step back and conduct a more scientific review of all of the antenna analyzers on offer, there for you should get sick of my postings over the next couple of weeks/months. I must say that the ability to save and analyze data on the lap top is an appealing feature. Regards Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm Have a look at the AIM 4170 at http://www.arraysolutions.com/ I have that and a MFJ analyzer. For a quick antenna adjustment, the MFJ is easier to use. For in depth analysis, the AIM can't be beat. If I had only one, I would prefer to have the AIM. -- Jim Pennino Remove .spam.sux to reply. |
MFJ-269 Antenna Analyzer experience
Dale Parfitt wrote:
"Peter" wrote in message Peter VK6YSF Again- look at the RigExpert A-200A. Batteries seem to last forever, it's USB upgradable and it DOES resolve the sign of R +/-JX. Dale W4OP Or, for a non-handheld device, the TenTec TAPR VNA (Vector Network Analyzer) works quite well (albeit it, too, has a broadband detector). I've used it with both the PC software and CocoaVNA on a Mac. The N2PK VNA has a more narrow band detector, but isn't available as a off-the-shelf box. Kind of depends on what you want to do with it. I have a MFJ-269 (and a 259, as it happens), and it's a really handy tool when standing under the antenna or doing "pruning" and those sorts of things, where you basically are "spin the frequency knob and look for the dip". I don't know that I'd use it as a precision measurement instrument to measure inductors and capacitors. .. BTW, the whole "doesn't show the sign of X" isn't a big deal in practice. A small bump of the frequency dial shows that X is either getting bigger or smaller as frequency goes up or down. If your impedance is varying so fast with frequency that you can't figure it out, the MFJ isn't for you anyway, since it's a fairly imprecise oscillator anyway. If you are looking to do precision measurements of impedance at a bunch of points, as you write them down or plot them, it's obvious, and, in any case, it's not a great tool for that. If you're looking to do something like adjust a phased array, you need one of the network analyzers. It's a lot better than trying to use this thing and opens/shorts, etc. |
MFJ-269 Antenna Analyzer experience
"Peter" wrote in
. au: "Dale Parfitt" wrote in message ... "Peter" wrote in message ... "Owen Duffy" wrote in message ... "Peter" wrote in . au: ... I must admit I had assumed that the 269 analyzer display the sign of the reactance, I will have to reread the ad. Ah, you were looking for honesty in advertising! The online guff on the MFJ259B says: "Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees)." The MFJ259B definitely does *not* show phase angle or reactance as negative for cases where X is actually negative. The same words appear in the MFJ269 online page, so it may also be a misrepresentation. I see in the MFJ269 manual, the same pretence over the sign of phase and reactance. It contains the words "Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase difference between current and voltage at the terminals of the analyzer." Of course, a phase angle between "zero and 90 degrees" does not represent "phase difference between current and voltage at the terminals of the analyzer" in the case of a capacitive impedance. Honesty in advertising... think again. Owen What was I thinking! I was impressed with what was being claimed. I will continue with my product research and you can expect me to float some other manufactures device on this group soon for comments. Peter VK6YSF Again- look at the RigExpert A-200A. Batteries seem to last forever, it's USB upgradable and it DOES resolve the sign of R +/-JX. Dale W4OP Thanks Dale I have just had a look at the RigExpert site. Look impressive, but the MFJ269 at about $400US was about my limit. I think I will take a step back and conduct a more scientific review of all of the antenna analyzers on offer, there for you should get sick of my postings over the next couple of weeks/months. I must say that the ability to save and analyze data on the lap top is an appealing feature. Peter, It helps to identify what you really need from the instrument. The difficulty in doing that is foreseeing where an unstructured learning journey might take you. You will tend to arrive a points where you want to measure something just beyond your existing capability. If the quest is for pure learning, then just concentrate on the things that are within scope, and enjoy the learning. I admit that it is a bit of an old world view of ham radio, that it is quintessentially a technical learning activity... but call me a dinasour. The resolution of sign with the '259B is not a show stopper, but it is a convenience issue and in the hands of a person with inadequate knowledge, it is potentially misleading. TLLC (http://www.vk1od.net/calc/tl/tllc.php) can refer impedance made at one point on a known transmission line (eg the tx end) to another point (eg the load end). Of course, uncertainty of the TL parameters contributes to measurement uncertainty. This technique is ok for one off measurements, but would be very labour intensive for a sweep with hundreds of observations. The ability to calibrate the feedline 'fixture' as part of a VNA measurement system provides the convenience of measurement referred to your preferred reference plan. The AIM4170 is (as I understand it) half of a VNA, but that should be enough to do the same thing. So, for the advantages of the ham grade VNA over the MFJ259B, you pay more money, get better measurement resolution (the AD converters have better resolution than the MFJ259B), have capability for automation of measurement referred to a convenient reference plane, but... you lose portability... though there is no reason why a ham grade VNA with a basic display system couldn't be portable. Owen |
MFJ-269 Antenna Analyzer experience
The ability to calibrate the feedline 'fixture' as part of a VNA measurement system provides the convenience of measurement referred to your preferred reference plan. The AIM4170 is (as I understand it) half of a VNA, but that should be enough to do the same thing. So, for the advantages of the ham grade VNA over the MFJ259B, you pay more money, get better measurement resolution (the AD converters have better resolution than the MFJ259B), have capability for automation of measurement referred to a convenient reference plane, but... you lose portability... though there is no reason why a ham grade VNA with a basic display system couldn't be portable. Owen The fixture cal is a pretty standard feature of all the ham VNAs (AIM 4170, TAPR VNA, N2PK) whether one or two port devices. Making it portable is something I've been toying with.. The software is not that complex (at least for the TAPR VNA), so running it on a PDA velcroed to the top of the box isn't out of the question. One problem is that the TAPR VNA is a USB slave, and most PDAs can't be a USB master. Maybe a small touchscreen netbook? Granted, you're now talking $1000 for the complete setup, but you'll have a real portable powerhouse, much like the Anritsu SiteMaster at 1/10th the cost. http://www.us.anritsu.com/products/S...QSidZ1016.aspx I've also contemplated making something like a S-parameter test set for the TAPR VNA (so you can do both directions) with a built in eCal. Basically just high quality relays and terminations is what's needed. Another useful add-on would be something that turns the VNA into a spectrum analyzer (e.g. use the output as the LO to a mixer followed by a BPF).. There's a lot of other problems with this, though. |
MFJ-269 Antenna Analyzer experience
On Sun, 16 Aug 2009 11:29:16 +0800, "Peter" wrote:
Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. I can't provide any info on the MFJ269, but I wonder whether the MFJ993B automatic antenna tuner might serve a similar purpose, with two big advantages over the 269. One is that it relies on your transmitter rather than on an internal RF source so it is less likely to be overwhelmed by nearby broadcast transmitters; and the other is that it is also a decent antenna tuner. The 993B uses some of the same circuits found in the 259. Of course, there are some things the 269 will do that the 993B won't help with. 73, Chuck NT3G |
MFJ-269 Antenna Analyzer experience
I have an earlier version, the MFJ249 and it works very well.
"Peter" wrote in message . au... Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. -- Peter VK6YSF http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm |
MFJ-269 Antenna Analyzer experience
I have just had a look at the RigExpert site. Look impressive, but the MFJ269 at about $400US was about my limit. I think I will take a step back and conduct a more scientific review of all of the antenna analyzers on offer, there for you should get sick of my postings over the next couple of weeks/months. I must say that the ability to save and analyze data on the lap top is an appealing feature. Peter, It helps to identify what you really need from the instrument. The difficulty in doing that is foreseeing where an unstructured learning journey might take you. You will tend to arrive a points where you want to measure something just beyond your existing capability. If the quest is for pure learning, then just concentrate on the things that are within scope, and enjoy the learning. I admit that it is a bit of an old world view of ham radio, that it is quintessentially a technical learning activity... but call me a dinasour. The resolution of sign with the '259B is not a show stopper, but it is a convenience issue and in the hands of a person with inadequate knowledge, it is potentially misleading. TLLC (http://www.vk1od.net/calc/tl/tllc.php) can refer impedance made at one point on a known transmission line (eg the tx end) to another point (eg the load end). Of course, uncertainty of the TL parameters contributes to measurement uncertainty. This technique is ok for one off measurements, but would be very labour intensive for a sweep with hundreds of observations. The ability to calibrate the feedline 'fixture' as part of a VNA measurement system provides the convenience of measurement referred to your preferred reference plan. The AIM4170 is (as I understand it) half of a VNA, but that should be enough to do the same thing. So, for the advantages of the ham grade VNA over the MFJ259B, you pay more money, get better measurement resolution (the AD converters have better resolution than the MFJ259B), have capability for automation of measurement referred to a convenient reference plane, but... you lose portability... though there is no reason why a ham grade VNA with a basic display system couldn't be portable. Owen Owen I would never call you a dinasour or should I say from one dinasour to another! I agree with your sentiments entirely of ham radio being a technical learning activity. For me the outlay for any antenna analyzer is significant, but I'm prepared to pay a bit for the instrument that covers foreseeable needs, but that will be as you say will cater for measurements just beyond my current capability. Let the evaluation continue. Regards Peter |
MFJ-269 Antenna Analyzer experience
Ian Wade G3NRW wrote:
The other nice thing about the 4170 is the ability to control it remotely. With the 4170 connected to the antenna system in the shack and controlled by a local PC, it's then possible to remotely access the PC from a cheapy notebook in the backyard. You can make antenna adjustments out in the yard and see the effects of the changes immediately, without having to repeatedly walk back indoors to look at the 4170 PC. This feature alone has saved me a *lot* of time: I tend to make my SWR readings right at the antenna, whenever possible. That length of coax to the xceiver will only make it look better in most cases. - 73 de Mike N3LI - |
MFJ-269 Antenna Analyzer experience
Michael Coslo wrote:
Ian Wade G3NRW wrote: The other nice thing about the 4170 is the ability to control it remotely. With the 4170 connected to the antenna system in the shack and controlled by a local PC, it's then possible to remotely access the PC from a cheapy notebook in the backyard. You can make antenna adjustments out in the yard and see the effects of the changes immediately, without having to repeatedly walk back indoors to look at the 4170 PC. This feature alone has saved me a *lot* of time: I tend to make my SWR readings right at the antenna, whenever possible. That length of coax to the xceiver will only make it look better in most cases. - 73 de Mike N3LI - One of the advantages of the 4170 is the ability to calibrate out the effects of the feedline. -- Jim Pennino Remove .spam.sux to reply. |
MFJ-269 Antenna Analyzer experience
On Sun, 16 Aug 2009 11:29:16 +0800, "Peter" wrote:
Hi all I'm looking at purchasing an MFJ269 antenna analyser and keen to hear experience of others in this group regarding this or similar analysers. Appears to be ideal if it is as good as MFJ claim. My only complaint is the little switch on the face of the unit that is depressed to enable measuring UHF SWR. It must be depressed ONLY if the unit is already powered up. If it is depressed before you power up, as I understand, some of the solid state parts may burn out when you power up. The 259 model does not have this problem, as it only measures up through the VHF range. Operation is limited in the UHF range of about 415-470 MHz -- you can only take SWR measurements. Bob k5qwg |
MFJ-269 Antenna Analyzer experience
From: Michael Coslo
Date: Fri, 21 Aug 2009 Time: 09:51:05 I tend to make my SWR readings right at the antenna, whenever possible. That length of coax to the xceiver will only make it look better in most cases. - 73 de Mike N3LI - Mike, With the 4170 I can calibrate the instrument to compensate for the feeder impedance. After calibration, the indicated impedance at the TX end of the feeder is actually the antenna feedpoint impedance. This makes life a *lot* easier. -- 73 Ian, G3NRW |
MFJ-269 Antenna Analyzer experience
Ian Wade G3NRW wrote:
From: Michael Coslo Date: Fri, 21 Aug 2009 Time: 09:51:05 I tend to make my SWR readings right at the antenna, whenever possible. That length of coax to the xceiver will only make it look better in most cases. - 73 de Mike N3LI - Mike, With the 4170 I can calibrate the instrument to compensate for the feeder impedance. After calibration, the indicated impedance at the TX end of the feeder is actually the antenna feedpoint impedance. This makes life a *lot* easier. Oaky, well good enough. My vertical uses a stub on the feedline, so I have to be out there anyhow.with a connector in the line. Seems like 6 of one, half dozen of the other situation. - 73 De Mike N3LI - |
MFJ-269 Antenna Analyzer experience
Ian Wade G3NRW wrote:
Mike, With the 4170 I can calibrate the instrument to compensate for the feeder impedance. After calibration, the indicated impedance at the TX end of the feeder is actually the antenna feedpoint impedance. This makes life a *lot* easier. Easy, yes. But If you're not careful, this can be a great example of garbage in, garbage out. I frequently calculate out the feedline transformation when making antenna measurements. But it's essential that you realize a small error in estimating the feedline loss(*) or length can sometimes result in a very large error in calculated impedance. This is particularly true if there's a large impedance mismatch between the line and antenna. Transmission line impedance, which can vary a lot from the specified nominal value (I've seen +/-20% with coax, more with ladder line), also has an effect on the result. So whenever I need accurate results or whenever the line Z0 is quite different from the antenna impedance, I start by carefully measuring the properties of the actual transmission line I'll be using. If you're not convinced, spend a few minutes playing with something like N6BV's TLW calculator that comes with the ARRL Antenna Book. (*) Some simplified techniques ignore transmission line loss altogether. This can lead to very inaccurate results in some situations. And loss is often quite different than the specified value, so it really has to be measured if it makes a significant difference. Roy Lewallen, W7EL |
MFJ-269 Antenna Analyzer experience
Roy Lewallen wrote:
Ian Wade G3NRW wrote: Mike, With the 4170 I can calibrate the instrument to compensate for the feeder impedance. After calibration, the indicated impedance at the TX end of the feeder is actually the antenna feedpoint impedance. This makes life a *lot* easier. Easy, yes. But If you're not careful, this can be a great example of garbage in, garbage out. I frequently calculate out the feedline transformation when making antenna measurements. But it's essential that you realize a small error in estimating the feedline loss(*) or length can sometimes result in a very large error in calculated impedance. This is particularly true if there's a large impedance mismatch between the line and antenna. Transmission line impedance, which can vary a lot from the specified nominal value (I've seen +/-20% with coax, more with ladder line), also has an effect on the result. So whenever I need accurate results or whenever the line Z0 is quite different from the antenna impedance, I start by carefully measuring the properties of the actual transmission line I'll be using. If you're not convinced, spend a few minutes playing with something like N6BV's TLW calculator that comes with the ARRL Antenna Book. (*) Some simplified techniques ignore transmission line loss altogether. This can lead to very inaccurate results in some situations. And loss is often quite different than the specified value, so it really has to be measured if it makes a significant difference. Roy Lewallen, W7EL The 4170 makes this a lot easier as you can measure the feedline actual parameters as well as calibrate out their effects. -- Jim Pennino Remove .spam.sux to reply. |
MFJ-269 Antenna Analyzer experience
Roy Lewallen wrote:
Ian Wade G3NRW wrote: Mike, With the 4170 I can calibrate the instrument to compensate for the feeder impedance. After calibration, the indicated impedance at the TX end of the feeder is actually the antenna feedpoint impedance. This makes life a *lot* easier. Easy, yes. But If you're not careful, this can be a great example of garbage in, garbage out. I frequently calculate out the feedline transformation when making antenna measurements. But it's essential that you realize a small error in estimating the feedline loss(*) or length can sometimes result in a very large error in calculated impedance. Most of the new analyzers that do "fixture cal" actually measure the line, so you're not doing any estimating. Somewhere in the future, as hams get more familiar with this kind of thing, I see folks installing a little relay box at the feedpoint of the antenna that has a short, open, and load, as well as the antenna. I've done this with an RCS-8V, modifying it to add a noninductive 50 ohm load and to short one of the relays. I then use my VNA to calibrate the relay box (or, more accurately, to just confirm that the load and short is good enough) with a short test cable. After I went through the hassle of modifying, I realized that I would have actually been better off to just get 50 ohm loads with PL-259s on them and PL-259 shorts. oh well, it's done now. So anyway, the RCS-8V has 5 ports and a common. I hook the the feedline on port 1, the antenna on port 5, the short on port 2 and the load on port 3. (Sometime in the future, I'm going to hook a phase reversing transformer on port 4). By turning on and off the various ports, I can connect loads and shorts to antennas and/or feedlines or leave them open. In a real fancy application, I'd put a remote controlled antenna tuner with a few extra relays in it at the feedpoint. Hmm.. another project to languish half completed in my garage for years. |
MFJ-269 Antenna Analyzer experience
From: Michael Coslo
Date: Fri, 21 Aug 2009 Time: 15:05:13 Oaky, well good enough. My vertical uses a stub on the feedline, so I have to be out there anyhow.with a connector in the line. Seems like 6 of one, half dozen of the other situation. - 73 De Mike N3LI - Agreed. But I guess your antenna feedpoint is more-or-less at ground level. That's a little different from peering through binoculars at an MFJ suspended at the feedpoint 50ft above ground .... grin -- 73 Ian, G3NRW |
MFJ-269 Antenna Analyzer experience
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MFJ-269 Antenna Analyzer experience
Michael Coslo wrote:
wrote: The 4170 makes this a lot easier as you can measure the feedline actual parameters as well as calibrate out their effects. This is a dumb question on my part, but what you are saying is that the mitigating effects that the cable has on the VSWR, making it look better in general, can not only be calculated and "calibrated out", but that the actual SWR of your antenna at the feedpoint is then given? As you get closer to 1.1:1 at the actual antenna, would accuracy then suffer? If feedline loss can bring an antenna that is not near that to a level approaching that, wouldn't it mean that teh calibration is somewhere in the noise? Like I say, this could be a really stoopid question. - 73 de Mike N3LI - Basically what you do is calibrate the instrument at the measurement point, whether that point is the instrument connector or at the end of a length of coax. You attach an open, a short and a known resistance; 50 ohms by default but it is user definable. The instrument than frequency sweeps and stores the results in a user definable calibration file. When you make a measurement of an unknown, you define which calibration file to use and the instrument corrects the readings to display the characteristics at the measurement point. Given that this is a $500 insturment and not a $20,000 labratory instrument there are going to be limits to how accurate all this is. After having used the AIM for a while, my opinion is that it far execeeds what is required for practical amateur usage. If you want to see some actual numbers, you can find a comparison of the results of an AIM 4170 compared to HP lab equiment at: http://www.bnk.com/w0qe/AIM4170_page1.html -- Jim Pennino Remove .spam.sux to reply. |
MFJ-269 Antenna Analyzer experience
Michael Coslo wrote:
wrote: The 4170 makes this a lot easier as you can measure the feedline actual parameters as well as calibrate out their effects. This is a dumb question on my part, but what you are saying is that the mitigating effects that the cable has on the VSWR, making it look better in general, can not only be calculated and "calibrated out", but that the actual SWR of your antenna at the feedpoint is then given? As you get closer to 1.1:1 at the actual antenna, would accuracy then suffer? If feedline loss can bring an antenna that is not near that to a level approaching that, wouldn't it mean that teh calibration is somewhere in the noise? Like I say, this could be a really stoopid question. - 73 de Mike N3LI - Not at all. Imagine that you have a very lossy line. You'll read very nearly the cable Z0 regardless of what's at the other end. Extreme changes in far-end impedance will make very little difference at the input end, so it's impossible to tell with any accuracy what's at the far end by looking at the near-end impedance. Another case to consider is one where the Z0 of the cable is very different than the Z of the load. In that case, a tiny change in line Z0, length, or loss changes the input Z for a given load Z. It can be impossible to measure the line length, impedance, or loss with sufficient accuracy to find the far end impedance with decent accuracy. This doesn't mean you can't get measurements good enough for amateur or even professional use. But on the other hand, your measurements can be total garbage in spite of your cable measurements if you fail to realize just how sensitive the result can be to small errors. A careful experimenter will do a sensitivity analysis which tells how large an error in results is caused by an error in measuring the feedline or in the input impedance measurement, then the probable measurement errors are estimated to determine the probable error in the calculated result. While a mathematical sensitivity analysis is the rigorous way to do this, something like N6BV's TLW program is just fine for most amateur purposes. Or, if you're using one of the instruments that does the calculation for you, try telling it the line is a few percent longer or shorter, or has a Z0 or loss a few percent different from what it said or you measured. See how much it changes the result. If the change is small, no problem. But if it's large, it means that extreme care and maybe some other techniques have to be used to get a good measurement. Let me give an example, done with TLW. Suppose we're measuring the impedance of an antenna at 30 MHz through 100 feet of RG-8x. TLW gives these nominal values for RG-8x: Z0 - 50.2 - j0.47 Velocity factor - 0.8 Loss - 1.926 dB/100' And suppose that these are exactly what our measurement of the cable said. We measure 21 + j20 at the input end, and conclude that the impedance of the antenna is 374 - j84 ohms. But suppose the measurement at the input end was inaccurate by about 5%, and that the actual input end Z was 21 + j20. Then the load Z is 322 - j105, about 15% off in R, 25% in Z. Or maybe the cable measurement was off by just 1%, and the cable is really 101 and not 100 feet long. In that case, the antenna Z is really 129 + j166 ohms. We're even on the other side of resonance from where we thought. Or maybe the velocity factor was rounded a bit and it's really closer to 0.81 than 0.8. How much difference would that small error make? Well, the antenna Z would be 53 - j120 ohms with our input measurement of 21 + j20! So, what's the real antenna impedance? 374 - j84, 322 - j105, 129 + j166, or 53 - j120? You're fooling yourself if you think you really know. It's easy to get lulled into believing that just because we read a value to six decimal places, it's accurate. But you're usually doing very well to get within a few percent in spite of all those digits. And when that few percent results in a much bigger error in calculated results, it's even more important to realize the limitations of your accuracy. Roy Lewallen, W7EL |
MFJ-269 Antenna Analyzer experience
Corrections:
I apologize, and misinterpreted my scribbled notes. The conclusion is the same, but some of the quoted numbers are a little off. Here are the correct ones. ------------ And suppose that these are exactly what our measurement of the cable said. We measure 21 + j20 at the input end, and conclude that the impedance of the antenna is 322 - j105 ohms. But suppose the measurement at the input end was inaccurate by about 5%, and that the actual input end Z was 22 + j21. Then the load Z is 273 - j125, about 15% off in R, 20% in X. . . ------------- Roy Lewallen wrote: And suppose that these are exactly what our measurement of the cable said. We measure 21 + j20 at the input end, and conclude that the impedance of the antenna is 374 - j84 ohms. But suppose the measurement at the input end was inaccurate by about 5%, and that the actual input end Z was 21 + j20. Then the load Z is 322 - j105, about 15% off in R, 25% in Z. . . |
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