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Analyzer evaluation
Group..I've just discovered this group (what took me so long?) and am
impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX |
"Darrell Gordon W4CX" wrote in message ... Group..I've just discovered this group (what took me so long?) and am impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX Hi Darrell guru, schmuru you will find the gamut of experience and education here, though as well as some amazing flame wars I have the MFJ with 450 and it works OK Only measures SWR on 450. It's not a laboratory instrument, but I have used it for years and it gets the job done. Priceless for setting up the HF mobile. I have no comparative experience except with an old General Radio bridge in my AM radio days decades ago. 73 H. NQ5H |
On Thu, 26 Aug 2004 17:23:18 +0000 (UTC), "Reg Edwards"
wrote: Is this recommendation of yours traceable directly to International Measurement Standards or has it passed through the hands of a sales department? Hi Punchinello, Your hedged question belies an ignorance of premium equipment that has been dominant in the field for 50 years. How is it you fail to recommend what you use? I have calibrated such in a Primary Electronic Standards Lab against standards traceable to NBS at the time. [but you knew this already] I did such work under contracts to Boeing, and the model I own was acquired from Boeing complete with certificates of traceability(not my own work, I have only on occasion found a piece of precision gear with my stickers on it). I have never encountered a GR 1606 that fell outside of its specifications - except for one where someone apparently burnt out one bridge component, a resistor. Undoubtedly this was accomplished by applying a transmitter to the excitation port - one can only imagine the fate of equipment connected to the detector port. This was very simple to recover from (one resistor). The instrument is robust and built like a Swiss precision watch. There are very few things that could go wrong and only under physical duress (like dropping it down three floors of stairs). 73's Richard Clark, KB7QHC |
I have an MFJ 269 and a GR 1606A. Each has its place.
At my location, about 10-15 miles from a hilltop with powerful TV, FM, and I believe AM broadcast transmitters, the MFJ is pretty useless for most antenna measurements. The impinging RF confuses it. It's great for fiddling with circuits on the bench, quick measurements of coax length, and checking the resonance of a 2 meter whip. I'm sure the RF problem would be the same for the other analyzers. Years ago, I rented an HP vector impedance meter for a consulting job, and it too was unable to handle the RF environment. A friend lent me an ancient tube-type Z meter that had a tunable detector, and I ended up making the measurements with it. (That was before I got the 1606A.) I use the 1606A when I need to make serious and accurate antenna measurements. It's tedious to use, having to be calibrated at the measurement frequency before making measurements. It only goes up to 60 MHz. And it requires an external signal generator and detector. The external detector is really its strength, though, since by using a narrowband detector (I use an old ICOM R1 portable receiver) I can make good measurements in the RF environment I live in. It would be a real nuisance to haul it up a tower, although you can put it on top of a stepladder. Sorry, I haven't used any of the other analyzers so can't help you out with the comparison between them. Roy Lewallen, W7EL Darrell Gordon W4CX wrote: Group..I've just discovered this group (what took me so long?) and am impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX |
On Thu, 26 Aug 2004 12:26:54 -0700, Roy Lewallen wrote:
I have an MFJ 269 and a GR 1606A. Each has its place. At my location, about 10-15 miles from a hilltop with powerful TV, FM, and I believe AM broadcast transmitters, the MFJ is pretty useless for most antenna measurements. The impinging RF confuses it. It's great for fiddling with circuits on the bench, quick measurements of coax length, and checking the resonance of a 2 meter whip. I'm sure the RF problem would be the same for the other analyzers. Years ago, I rented an HP vector impedance meter for a consulting job, and it too was unable to handle the RF environment. A friend lent me an ancient tube-type Z meter that had a tunable detector, and I ended up making the measurements with it. (That was before I got the 1606A.) I use the 1606A when I need to make serious and accurate antenna measurements. It's tedious to use, having to be calibrated at the measurement frequency before making measurements. It only goes up to 60 MHz. And it requires an external signal generator and detector. The external detector is really its strength, though, since by using a narrowband detector (I use an old ICOM R1 portable receiver) I can make good measurements in the RF environment I live in. It would be a real nuisance to haul it up a tower, although you can put it on top of a stepladder. Sorry, I haven't used any of the other analyzers so can't help you out with the comparison between them. Roy Lewallen, W7EL It's gratifying to learn that the 'ole 1606 is still being used by people in the group. About ten years ago I wondered what I'd do if anything happened to mine, especially since General Radio was already out of business, so I found a 1606-B for $400 as a backup. Son Rick, WB4GNR, is using it, but it's still my backup. Walt, W2DU |
I guess nobody just 'tunes for maximum smoke' any more
"Darrell Gordon W4CX" wrote in message ... Group..I've just discovered this group (what took me so long?) and am impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
And to think I've been tuning for minimum smoke all these years.
;^) "Hal Rosser" wrote in message .. . I guess nobody just 'tunes for maximum smoke' any more "Darrell Gordon W4CX" wrote in message ... Group..I've just discovered this group (what took me so long?) and am impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
My question: What are you guys using for HF measurements? The original Autek. Limited accuracy, but *very* portable and very useful. I'm building the N2PK Vector Network Analyzer, which is only good to 60Mhz, with laboratory accuracy. Paul has hinted at extensions to allow se to 450Mhz. See www.n2pk.com . The GR bridges suggested are very good, but not too portable. 73, John - K6QQ |
On Thu, 26 Aug 2004 14:08:33 -0700, "John Moriarity"
wrote: | | My question: What are you guys using for HF measurements? | |The original Autek. Limited accuracy, |but *very* portable and very useful. | |I'm building the N2PK Vector Network |Analyzer, which is only good to 60Mhz, |with laboratory accuracy. Paul has hinted |at extensions to allow se to 450Mhz. |See www.n2pk.com . Me too. Well, let me rephrase... I have had the kit ($220) for about 8 months and have yet to start on it ;) First I figured I needed a better, smaller soldering iron. $100. Then I got that and realized I can't see the parts. Got a 10X Optivisor. $35. Depth of field is really marginal. Got a lighted magnifier. $50. Ready to go... oops no anti-static mat and right in the middle of building bathroom vanity cabinet. Figured I could save money by DIY. New Delta Unisaw. $1500. Dovetail jig. $400. Better lighting in garage $400. Hardwood $400. Misc router bits, finishing materials, spray gun, screws, door and drawer hardware and my labor at $0.05/ hour... don't ask. Other than that, I use a Boonton 250 or an HP 8405 for impedance measurements. |
Hi Darrell, I have used the Autek VA1 and the MFJ 259B here in 9V for about a year. Must have gotten a good Autek as it has performed well. All of the MFJ series I have used in the past and they will do the job but as has been said, high RF enviornments render it useless. The MFJ that goes to UHF we used on a field day trip to a remote island just off 9V and it also did a good job. YMMV but the VA1 goes into a pocket for a tower climb, is a bit fiddley, but I find I use it more than the MFJ. 73 Bob 9V1GO |
I use the MFJ - because I could afford it at the time.
....and this analyzer post gives me an idea about the Stainless-steel wire thread - hmmm "Darrell Gordon W4CX" wrote in message ... Group..I've just discovered this group (what took me so long?) and am impressed with the knowledge here. I am shopping for an antenna analyzer and am stymied by the choices (or lack thereof). In all of hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi to choose from. I've checked eham reviews and found that the AEA VIA (not Bravo) rates highest...and most expensive. Probably worth it. Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I know this is impossible, and would be willing to go with separate units (Autek), but they have awful reviews quality. My question: What are you guys using for HF measurements? What about V/UHF measurements? Do you recommend any particular model? How about used HP gear from ebay (yes, I know the risks). V/UHF is my priority since I'm building some copper loops for 6 and 2. What say you sage antenna gurus? Darrell W4CX --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.744 / Virus Database: 496 - Release Date: 8/24/2004 |
The only thing wrong with the Autek is its internal oscillator has only a
few microwatts output. And for the few components inside it, it is overpriced. --- Reg |
I use a GR 1606A when its capabilities are needed. I even salvaged
another from being scraped so I have a back-up. However, for most tasks, I find that the AEA VIA is the cat's meow. For instance, when trying to tune a Matchbox to strange frequencies, the VIA tells one which way things are going. I have not tried to use the VIA in the presence of strong broadcast transmitters. At work, we have HP (Agelent) network analyzers and standards to use as comparisons. AEA also makes, and I use, a modest TDR that is good enough to be used to keep track of transmission lines, connectors, and in-line protection devices. As Roy, and others, have said: when you need a GR, you need a GR. Before I bought a 1606, I was once loaned the 900 something predecessor to the 1606. This instrument is inside of a small, copper lined suitcase and the particular instrument had been used by the military since about WW2. The outside showed use. It was spot on with my standards and, when I opened up the case, the insides were still bright and shinny. GR made quality instruments. Though I have not used it, somewhere I have a Delta bridge that was given to me. Go for the VIA for HF. You will not be disappointed. 73, Mac N8TT -- J. Mc Laughlin - Michigan USA Home: "Roy Lewallen" wrote in message ... I have an MFJ 269 and a GR 1606A. Each has its place. |
Darrell, W4CX wrote:
"V/UHF is my priority since I`m building some copper loops for 6 and 2." In the U.S., General Radio is champion. But, in Europe we used a British Wayne Kerr UHF admittance bridge on lines and antennas in the middle of a high frequency broadcast plant with a dozen or more competing transmitters on the air at full power, as they always were. The secret of success is the bridge detector used. A Collins 51-J was useless, solid noise across the H-F bands. A Hammarlund SP-600 worked like a champ. Best regards, Richard Harrison, KB5WZI |
On Fri, 27 Aug 2004 09:18:23 -0400, "J. McLaughlin" wrote:
snip As Roy, and others, have said: when you need a GR, you need a GR. Before I bought a 1606, I was once loaned the 900 something predecessor to the 1606. This instrument is inside of a small, copper lined suitcase and the particular instrument had been used by the military since about WW2. The outside showed use. It was spot on with my standards and, when I opened up the case, the insides were still bright and shinny. GR made quality instruments. snip 73, Mac N8TT Hi Mac, The predecessor to the GR-1606A was the GR-916A, which was the cadillac of professional bridges prior to the GR-1606A, which came out in 1955. I used the 916A to adjust the tower resistance of WCEN, 1150 kHz, the station I engineered and built in 1948. The National HRO receiver was used as the detector. Walt, W2DU |
|
A very capable engineering colleage of mine mentioned some time ago that
an AEA he had purchased worked very well except for one thing -- the reference point appeared to be inside the instrument. He said it was as though there were another length of line (about 5 cm as I recall) inside. For example, measurement of a short circuit would indicate the amount of positive reactance you'd expect from such a line. This might not be too important for general purpose HF use, but would be a problem with some measurements, especially at high frequencies. It could be removed by mathematical adjustment of the measurement results, of course. I mentioned this problem to the AEA folks at Dayton, not long after it changed hands, and they might have fixed it. Do you see this phenomenon? I saw a similar thing when I spent a few minutes playing with the very first model of Autek. I don't see this with my MFJ. Again, the problem might have been fixed, but it's something to look for, particularly on an older used unit. Roy Lewallen, W7EL J. McLaughlin wrote: I use a GR 1606A when its capabilities are needed. I even salvaged another from being scraped so I have a back-up. However, for most tasks, I find that the AEA VIA is the cat's meow. For instance, when trying to tune a Matchbox to strange frequencies, the VIA tells one which way things are going. I have not tried to use the VIA in the presence of strong broadcast transmitters. At work, we have HP (Agelent) network analyzers and standards to use as comparisons. AEA also makes, and I use, a modest TDR that is good enough to be used to keep track of transmission lines, connectors, and in-line protection devices. As Roy, and others, have said: when you need a GR, you need a GR. Before I bought a 1606, I was once loaned the 900 something predecessor to the 1606. This instrument is inside of a small, copper lined suitcase and the particular instrument had been used by the military since about WW2. The outside showed use. It was spot on with my standards and, when I opened up the case, the insides were still bright and shinny. GR made quality instruments. Though I have not used it, somewhere I have a Delta bridge that was given to me. Go for the VIA for HF. You will not be disappointed. 73, Mac N8TT |
"Roy Lewallen" wrote in message ... A very capable engineering colleage of mine mentioned some time ago that an AEA he had purchased worked very well except for one thing -- the reference point appeared to be inside the instrument. He said it was as though there were another length of line (about 5 cm as I recall) inside. For example, measurement of a short circuit would indicate the amount of positive reactance you'd expect from such a line. This might not be too important for general purpose HF use, but would be a problem with some measurements, especially at high frequencies. It could be removed by mathematical adjustment of the measurement results, of course. I mentioned this problem to the AEA folks at Dayton, not long after it changed hands, and they might have fixed it. Do you see this phenomenon? I saw a similar thing when I spent a few minutes playing with the very first model of Autek. I don't see this with my MFJ. Again, the problem might have been fixed, but it's something to look for, particularly on an older used unit. Roy Lewallen, W7EL Hi Roy, I briefly owned the AEA V/U model- probably in 1999. Using my HP precision termination set, it appeared that the best VHF return loss was indicated when the analyzer was terminated in around 60 Ohms and for UHF it was 75 Ohms. When I called AEA to inquire, I was told "that's about the accuracy you should expect for $500". The Autek V/U instrument was in excellent agreement with an HP 8711B. Dale W4OP |
Thanks to all for a very informative thread. You guys are living up
to your reputation. Has anyone had any experience with an HP 8754? They seem to be around, and with a b/w of 4-1300Mhz might be an excellent choice??? Darrell |
Dear Roy:
Very interesting! It just did not occur to me to test. Now that the EMC book I have been helping with is finally being printed (over ten years in the crafting) I shall put an appraisal of the AEA on our list of activities. It occurs to me that almost all of my use of the instrument has been below about 10 MHz. At those frequencies, my suspicions probably were not tripped by a discrepancy of half a degree (or smaller). I did buy the instrument after at least one change of hands. Thank you very much for the heads-up. I am shaking my head in wonder that that property I never thought to check. Warm regards, Mac N8TT -- J. Mc Laughlin - Michigan USA Home: "Roy Lewallen" wrote in message ... A very capable engineering colleage of mine mentioned some time ago that an AEA he had purchased worked very well except for one thing -- the reference point appeared to be inside the instrument. He said it was as though there were another length of line (about 5 cm as I recall) inside. For example, measurement of a short circuit would indicate the amount of positive reactance you'd expect from such a line. This might not be too important for general purpose HF use, but would be a problem with some measurements, especially at high frequencies. It could be removed by mathematical adjustment of the measurement results, of course. I mentioned this problem to the AEA folks at Dayton, not long after it changed hands, and they might have fixed it. Do you see this phenomenon? I saw a similar thing when I spent a few minutes playing with the very first model of Autek. I don't see this with my MFJ. Again, the problem might have been fixed, but it's something to look for, particularly on an older used unit. Roy Lewallen, W7EL |
J. McLaughlin wrote:
"Roy Lewallen" wrote in message ... A very capable engineering colleage of mine mentioned some time ago that an AEA he had purchased worked very well except for one thing -- the reference point appeared to be inside the instrument. He said it was as though there were another length of line (about 5 cm as I recall) inside. For example, measurement of a short circuit would indicate the amount of positive reactance you'd expect from such a line. This might not be too important for general purpose HF use, but would be a problem with some measurements, especially at high frequencies. It could be removed by mathematical adjustment of the measurement results, of course. I mentioned this problem to the AEA folks at Dayton, not long after it changed hands, and they might have fixed it. Do you see this phenomenon? I saw a similar thing when I spent a few minutes playing with the very first model of Autek. I don't see this with my MFJ. Again, the problem might have been fixed, but it's something to look for, particularly on an older used unit. Dear Roy: Very interesting! It just did not occur to me to test. Now that the EMC book I have been helping with is finally being printed (over ten years in the crafting) I shall put an appraisal of the AEA on our list of activities. It occurs to me that almost all of my use of the instrument has been below about 10 MHz. At those frequencies, my suspicions probably were not tripped by a discrepancy of half a degree (or smaller). I did buy the instrument after at least one change of hands. Thank you very much for the heads-up. I am shaking my head in wonder that that property I never thought to check. Warm regards, Mac N8TT A few years ago, I was evaluating an AEA-CIA for a possible magazine review. One of the tests involved a load consisting of some metres of 50 ohm coax terminated in three paralleled 50 ohm chip resistors. When the frequency is swept, this load walks around the SWR=3 circle on a Smith chart, giving |Z| values ranging between 16 ohms and 150 ohms with a progressively rotating phase; or equivalent results in terms of (R+/-jX). In other words, the test involves only moderately high or low impedances with no nasty surprises. The AEA-CIA gave good results as a frequency-sweeping SWR meter, and the graphical display is unique in this price range; but unfortunately but it did not give sensible results in the R-X mode (the mode that gives the "Complex Impedance Analyser" its name). In a frequency range where the true value of X was falling progressively through zero, the indicated value came down correctly to about 30 ohms - and then suddenly jumped to 0.0. The R readings continued to change with frequency exactly as expected, but the X reading stayed 'stuck' at precisely 0.0 until the sweep reached the frequency at which X changed sign, whereupon the X readings started to make sense again. This behaviour was totally reproducible. Also, the AEA-CIA is also supposed to be able to resolve the sign of the complex impedance (which it presumably does by changing frequency and noting what happens to X), but perhaps not surprisingly this didn't work reliably either. At a constant frequency where the value of X was nowhere close to zero, the instrument was often unable to make up its mind about the correct sign. All these symptoms looked like firmware problems to me. Since R and X are both computed from the same analog voltage readings, and R was correct while X was not, the problem had to be in the computation. The AEA management at the time were quick to respond through the UK dealer. They sent me schematics, and analog-type mods to try, and even replaced the entire instrument... which behaved exactly like the one before. However, they didn't seem to understand what I just wrote above, and didn't want to go anywhere near the firmware. In the end, I abandoned the effort and the UK dealer didn't import the instrument. The magazine decided we should review the MFJ-269 instead - which handled the same test load with good accuracy. Sorry, I don't recall what specific firmware versions gave these problems with the AEA-CIA, and have no information whether they have been fixed in later versions. As Roy said: the problem might have been fixed, but it's something to look for, particularly on an older used unit. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Dear Ian:
Most interesting. Thanks. I have not used the AEA-CIA for R-X measurements. I always assumed that firmware was used to guess at the sign of X, and it is not too surprising (though disappointing) that the chap who wrote the software might blank out small values of X altogether. [In a spherical navigation program that I wrote long ago for a slow computer, I flagged results that would have been in the noise because of round-off error. It took some effort to know when the results were bad. Others ignored error analysis, being enamored of many random digits, with disastrous results. Sometimes, with computers, no answer is the best one can do. As an example: Cramer's rule just does not work to solve some systems of linear equations using a computer! Even the HP48 uses an iterative technique, which computers are real good at and people are not.] The most interesting use that I made of the AEA-CIA, which would have been difficult to do with a GR bridge, was measuring the apparent surge impedance of a split boom to be used with a LPDA (prior to the elements being attached). Leaving out the appropriate lectu I terminated the split-boom with a series of resistors 'till the variation in SWR (seen at the other end of the split-boom) with frequency was minimal. [This is another example of SWR on a line depending on which way one is looking.] The strong suit of the AEA-CIA is in giving one repeatable data over a wide frequency range. Most of the antennas that I deal with have functional bandwidths of at least an octave. The value of the AEA-CIA is much reduced if one is only interested in what is going on in a narrow bandwidth. Thanks very much for sharing your experience. We have once again benefited from your experience and Roy's experience. 73 Mac N8TT -- J. Mc Laughlin - Michigan USA Home: "Ian White, G3SEK" wrote in message ... snip A few years ago, I was evaluating an AEA-CIA for a possible magazine review. One of the tests involved a load consisting of some metres of 50 ohm coax terminated in three paralleled 50 ohm chip resistors. When the frequency is swept, this load walks around the SWR=3 circle on a Smith chart, giving |Z| values ranging between 16 ohms and 150 ohms with a progressively rotating phase; or equivalent results in terms of (R+/-jX). In other words, the test involves only moderately high or low impedances with no nasty surprises. The AEA-CIA gave good results as a frequency-sweeping SWR meter, and the graphical display is unique in this price range; but unfortunately but it did not give sensible results in the R-X mode (the mode that gives the "Complex Impedance Analyser" its name). In a frequency range where the true value of X was falling progressively through zero, the indicated value came down correctly to about 30 ohms - and then suddenly jumped to 0.0. The R readings continued to change with frequency exactly as expected, but the X reading stayed 'stuck' at precisely 0.0 until the sweep reached the frequency at which X changed sign, whereupon the X readings started to make sense again. This behaviour was totally reproducible. Also, the AEA-CIA is also supposed to be able to resolve the sign of the complex impedance (which it presumably does by changing frequency and noting what happens to X), but perhaps not surprisingly this didn't work reliably either. At a constant frequency where the value of X was nowhere close to zero, the instrument was often unable to make up its mind about the correct sign. All these symptoms looked like firmware problems to me. Since R and X are both computed from the same analog voltage readings, and R was correct while X was not, the problem had to be in the computation. The AEA management at the time were quick to respond through the UK dealer. They sent me schematics, and analog-type mods to try, and even replaced the entire instrument... which behaved exactly like the one before. However, they didn't seem to understand what I just wrote above, and didn't want to go anywhere near the firmware. In the end, I abandoned the effort and the UK dealer didn't import the instrument. The magazine decided we should review the MFJ-269 instead - which handled the same test load with good accuracy. Sorry, I don't recall what specific firmware versions gave these problems with the AEA-CIA, and have no information whether they have been fixed in later versions. As Roy said: the problem might have been fixed, but it's something to look for, particularly on an older used unit. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
J. McLaughlin wrote:
Most interesting. Thanks. You're welcome. Just one small point, though: I have not used the AEA-CIA for R-X measurements. I always assumed that firmware was used to guess at the sign of X, and it is not too surprising (though disappointing) that the chap who wrote the software might blank out small values of X altogether. In case anyone's not following this closely, I had been writing about the AEA-CIA blanking out values of X less than about 30 ohms. That is not "small" by any standard, and it only happened on one side of zero. It could not possibly have been a deliberate feature of the programming. In contrast, the MFJ-269 (and probably the 259B) does deliberately blank out small values - truly small values, that is - as X passes through zero. This occurs exactly as explained in the manual, and is exactly as it should be. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Walter Maxwell, W2DU listed an enviable collection of impedance
measuring devices. He`s prepared. Walter also wrote: "In my impedance-measuring arsenal is the Wayne Kerr B108 admittance bridge. The beautiful aspect of this bridge is that its unknown terminals are balanced, thus allowing direct measurement of balanced lines." Yes. Balanced unknown terminals are convenient for a commercial shortwave operator located away from the seashore. Horizontal wave polarization with balanced feedlines is economical as compared with coax for high power. Unbalanced vertical antennas are convenient for groundwaves to extend beyond the horizon for the mediumwave broadcaster. These antennas are conveniently fed by coax of the concentric pipe or skeletal types. All groundwaves are vertically polarized. These can travel very far at low and medium frequencies. Attenuation of high frequency groundwaves is severe. There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave. Bottom line is that shortwave broadcasters transmit from horizontal antennas and mediumwave broadcasters transmit from vertical antennas. For shortwave, the target is reached via the ionosphere. For mediumwave, the target is reached via the earth`s surface which is involved in reaching beyond the line of sight. For a dipole, you are likely to prefer a balanced bridge. For a monopole, you are likely to prefer an unbalanced bridge. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote - There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave. -------------------------------------------------------------- With a groundwaves there is no reflected wave and incident wave to get out of phase with each other. By definition, it is all in the ground down to one skin depth. Very simply, a horizontally polarised groundwave, with its horizontal current, suffers great attenuation in the loss resistance of the horizontal ground. It gets launched but after one or two wavelengths it is many decibels down. This is the reason why horizontally polarised noise, relatively locally generated, is smaller than the vertically polarised variety although, on the average, both are randomly generated with equal amplitudes. Half of the total noise power is dissipated in the ground except that which is generated immediately adjacent to your receiving antenna. ---- Reg, G4FGQ |
On Sun, 29 Aug 2004 09:31:13 +0000 (UTC), "Reg Edwards"
wrote: "Richard Harrison" wrote - There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave. -------------------------------------------------------------- With a groundwaves there is no reflected wave and incident wave to get out of phase with each other. By definition, it is all in the ground down to one skin depth. Reg, you are correct, of course, but Richard H. said above, "There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave." What Richard mean't concerning the 'reflected' wave is that the energy radiated downward from a horizontal antenna is reflected by the ground, and that reflected wave is out of phase with the incident wave. Walt, W2DU |
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Although a reflected horizontally polarized wave is out of phase with
the incident wave, and this explains the zero far field strength you get with horizontally polarized waves, I'm not sure this is the relevant explanation for the lack of ground wave propagation. The reason I doubt it is that if you do the same analysis for vertically polarized waves, you find that the net field strength is also zero at zero elevation angle, except for the special case where ground is perfectly conducting. So using the same analysis, you'd have to conclude that vertically polarized waves can't propagate by ground wave, either. Roy Lewallen, W7EL Walter Maxwell wrote: On Sun, 29 Aug 2004 09:31:13 +0000 (UTC), "Reg Edwards" wrote: "Richard Harrison" wrote - There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave. -------------------------------------------------------------- With a groundwaves there is no reflected wave and incident wave to get out of phase with each other. By definition, it is all in the ground down to one skin depth. Reg, you are correct, of course, but Richard H. said above, "There is no propagation of horizontally polarized groundwaves at all. The low-angle reflected wave is out of phase with the incident wave." What Richard mean't concerning the 'reflected' wave is that the energy radiated downward from a horizontal antenna is reflected by the ground, and that reflected wave is out of phase with the incident wave. Walt, W2DU |
Roy, W7EL wrote:
"So using the same analysis, you`d have to conclude that vertically polarized waves can`t propagate by ground wave either." I`ll turn to the authors for a source of my contention. Terman says in his 1955 edition on page 803: "The ground wave is vertically polarized, because any horizontal component of electric field in contact with the earth is short-circuited by the earth." And on page 808, Terman says: "Examination of these vector diagrams shows that with a perfect reflector the horizontal components of electric field will exactly cancel each other at the surface of the perfect conductor. In contrast, the vertical components of the electric field of the incident and reflected waves do not cancel, but rather add at the reflector surface with small values of earth reflection angle." Best regards, Richard Harrison, KB5WZI |
Roy, W7EL wrote:
"So using the same analysis, you`d have to conclude that vertically polarized waves can`t propagate by ground waves either." Earth isn`t perfectly conductive but even so permits propagation of vertically polarized waves. Another expert, Kraus says on page 412 of his 1950 edition of "Antennas": "The electric field of a wave traveling along a perfectly conducting surface is perpendicular to the surface....However, if the surface is an imperfect conductor, such as the earth`s surface or ground, the electric-field lines have a forward tilt near the surface.... Hence, the field at the surface has a vertical component Ey and a horizontal component Ex. The component Ex is associated with that part of the wave that enters the surface and is dissipated in heat. The Ey component continues to travel along the surface. Best regards, Richard Harrison, KB5WZI |
That's a much better explanation of the phenomenon of ground wave
analysis than the first one you put forth. Roy Lewallen Richard Harrison wrote: Roy, W7EL wrote: "So using the same analysis, you`d have to conclude that vertically polarized waves can`t propagate by ground waves either." Earth isn`t perfectly conductive but even so permits propagation of vertically polarized waves. Another expert, Kraus says on page 412 of his 1950 edition of "Antennas": "The electric field of a wave traveling along a perfectly conducting surface is perpendicular to the surface....However, if the surface is an imperfect conductor, such as the earth`s surface or ground, the electric-field lines have a forward tilt near the surface.... Hence, the field at the surface has a vertical component Ey and a horizontal component Ex. The component Ex is associated with that part of the wave that enters the surface and is dissipated in heat. The Ey component continues to travel along the surface. Best regards, Richard Harrison, KB5WZI |
Roy, W7EL wrote:
"That`s a much better explanation of the phenomenon of ground wave analysis than the first one you put forth." True! Kraus was a much better explainer than I will ever be, I fear. Best regards, Richard Harrison, KB5WZI |
On Mon, 30 Aug 2004 01:04:57 -0400, "Tim Perry"
wrote: "Walter Maxwell" wrote in message .. . snip I was just about to tell you what I use, but Richard, above, beat me to it. For HF measurements this bridge, the General Radio 1606-A, is the Cadillac of all bridges. It 's been the bridge of choice for nearly every AM broadcast engineer in determining t he impedance of AM broadcast antennas since it came on the market in 1955. i have yet to see one at a US broadcast station. the meter that is usually found, and used is the delta OIB-1 or OIB-3 http://www.deltaelectronics.com/data/oib1&3.htm Hi Tim, I can't disagree with you here, because my knowledge is from several years back. I'm not familiar the Delta except by reputation--all I've heard is that it's a good instrument. The demise of General Radio is probably one reason the GR instrument is no longer the instrument of choice, so the dividing line between use of the GR and the Delta probably defines the end of one era and the beginning of another. Walt, W2DU |
"Ian White, G3SEK" wrote in message ... J. McLaughlin wrote: Most interesting. Thanks. You're welcome. Just one small point, though: I have not used the AEA-CIA for R-X measurements. I always assumed that firmware was used to guess at the sign of X, and it is not too surprising (though disappointing) that the chap who wrote the software might blank out small values of X altogether. In case anyone's not following this closely, I had been writing about the AEA-CIA blanking out values of X less than about 30 ohms. That is not "small" by any standard, and it only happened on one side of zero. It could not possibly have been a deliberate feature of the programming. In contrast, the MFJ-269 (and probably the 259B) does deliberately blank out small values - truly small values, that is - as X passes through zero. This occurs exactly as explained in the manual, and is exactly as it should be. 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek Ian, and others, I have the 269 HF VHF UHF analyzer and noticed something strange. In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an otherwise good 75 ohm load (please assume I know how to tell and I used a low frequency to reduce errors) shows something like a 1.3 : 1 SWR. When I called to ask about it, the first tech at MFJ seemed confused and clearly did not understand. Another call, on another day resulted in a better tech, but the response was to send it in for re-calibration. This also seems to be a calculation rather than an adjustment, no? Once you know Z it is a simple calculation to get to SWR for another Zo. Or have I been smoking a bad brand...? Woha! I see they have on line calibration manual for the 259B & 269 on line! http://www.mfjenterprises.com/MFJ-259Bcalibration.php http://www.mfjenterprises.com/man/pd...alibration.pdf I don't see anything other than "watch the blinking SWR" .(sounds like a British insult) for the Advance 3 "calibration". -- Steve N, K,9;d, c. i My email has no u's. |
My MFJ 269 shows the SWR of a Tektronix 75 ohm termination as 1.0:1 up
to 77 MHz when Z0 is set to 75 ohms. Roy Lewallen, W7EL Steve Nosko wrote: Ian, and others, I have the 269 HF VHF UHF analyzer and noticed something strange. In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an otherwise good 75 ohm load (please assume I know how to tell and I used a low frequency to reduce errors) shows something like a 1.3 : 1 SWR. When I called to ask about it, the first tech at MFJ seemed confused and clearly did not understand. Another call, on another day resulted in a better tech, but the response was to send it in for re-calibration. This also seems to be a calculation rather than an adjustment, no? Once you know Z it is a simple calculation to get to SWR for another Zo. Or have I been smoking a bad brand...? Woha! I see they have on line calibration manual for the 259B & 269 on line! http://www.mfjenterprises.com/MFJ-259Bcalibration.php http://www.mfjenterprises.com/man/pd...alibration.pdf I don't see anything other than "watch the blinking SWR" .(sounds like a British insult) for the Advance 3 "calibration". |
"Walter Maxwell" wrote in message ... On Mon, 30 Aug 2004 01:04:57 -0400, "Tim Perry" wrote: "Walter Maxwell" wrote in message .. . snip I was just about to tell you what I use, but Richard, above, beat me to it. For HF measurements this bridge, the General Radio 1606-A, is the Cadillac of all bridges. It 's been the bridge of choice for nearly every AM broadcast engineer in determining t he impedance of AM broadcast antennas since it came on the market in 1955. i have yet to see one at a US broadcast station. the meter that is usually found, and used is the delta OIB-1 or OIB-3 http://www.deltaelectronics.com/data/oib1&3.htm Hi Tim, I can't disagree with you here, because my knowledge is from several years back. I'm not familiar the Delta except by reputation--all I've heard is that it's a good instrument. The demise of General Radio is probably one reason the GR instrument is no longer the instrument of choice, so the dividing line between use of the GR and the Delta probably defines the end of one era and the beginning of another. Walt, W2DU in part, the OIB (Operating Impedance Bridge) is popular because the normal transmitter is the (usual) frequency source and interruptions to transmissions can be brief or non-existent. in typical use the bridge is inserted using a hot jack or J plug. the engineer must be careful at all time to avoid touching exposed RF as the resulting burns are painful and long lasting. the meter itself has some effect on the circuit tuning: sometimes a permanent version is installed at the common point of a phased array. sometimes special jacks are employed that add a bit of inductance when the meter is removed. |
Steve Nosko wrote:
I have the 269 HF VHF UHF analyzer and noticed something strange. In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an otherwise good 75 ohm load (please assume I know how to tell and I used a low frequency to reduce errors) shows something like a 1.3 : 1 SWR. And it had correctly showed SWR=1.5 when Zo was set to 50 ohms? When I called to ask about it, the first tech at MFJ seemed confused and clearly did not understand. Another call, on another day resulted in a better tech, but the response was to send it in for re-calibration. This also seems to be a calculation rather than an adjustment, no? Once you know Z it is a simple calculation to get to SWR for another Zo. Or have I been smoking a bad brand...? I didn't check this feature as part of the review, but it should be simply the inverse ratio of whatever resistances you choose to define as your Zo values. Woha! I see they have on line calibration manual for the 259B & 269 on line! http://www.mfjenterprises.com/MFJ-259Bcalibration.php http://www.mfjenterprises.com/man/pd...alibration.pdf I don't see anything other than "watch the blinking SWR" .(sounds like a British insult) for the Advance 3 "calibration". The MFJ-269 had to go back after the review (which itself was a few years ago) so unfortunately I'm no longer able to check your findings, Steve. But don't recalibrate it yet, because that would be stirring-in additional variables which will muddy the waters right now. After the present question has been resolved, you may be able to give the calibration procedure a little more TLC than there was time for on the production-line - but you'll need some precision standards to do it. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
On Tue, 31 Aug 2004 02:37:31 -0400, "Tim Perry"
wrote: snip Hi Tim, I can't disagree with you here, because my knowledge is from several years back. I'm not familiar the Delta except by reputation--all I've heard is that it's a good instrument. The demise of General Radio is probably one reason the GR instrument is no longer the instrument of choice, so the dividing line between use of the GR and the Delta probably defines the end of one era and the beginning of another. Walt, W2DU in part, the OIB (Operating Impedance Bridge) is popular because the normal transmitter is the (usual) frequency source and interruptions to transmissions can be brief or non-existent. in typical use the bridge is inserted using a hot jack or J plug. the engineer must be careful at all time to avoid touching exposed RF as the resulting burns are painful and long lasting. the meter itself has some effect on the circuit tuning: sometimes a permanent version is installed at the common point of a phased array. sometimes special jacks are employed that add a bit of inductance when the meter is removed. Thanks, Tim, for the update on the OIB. It did refresh my memory concerning the meter being used while the transmitter is on the air. That I now recall. Walt, W2DU |
"Ian White, G3SEK" wrote in message ... Steve Nosko wrote: I have the 269 HF VHF UHF analyzer and noticed something strange. In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an otherwise good 75 ohm load (please assume I know how to tell and I used a low frequency to reduce errors) shows something like a 1.3 : 1 SWR. And it had correctly showed SWR=1.5 when Zo was set to 50 ohms? Yep! An extensive sheck of known good loads showed that the MFJ was working as expected with reasonable accuracy. I don't have numbers, but 50 ohm loads looked ok and SWR, Z etc all appeared to be reasonable. Just this one problem. (I have access to Agilent "N" cal kits) When I called to ask about it, the first tech at MFJ seemed confused and clearly did not understand. Another call, on another day resulted in a better tech, but the response was to send it in for re-calibration. This also seems to be a calculation rather than an adjustment, no? Once you know Z it is a simple calculation to get to SWR for another Zo. Or have I been smoking a bad brand...? I didn't check this feature as part of the review, but it should be simply the inverse ratio of whatever resistances you choose to define as your Zo values. Woha! I see they have on line calibration manual for the 259B & 269 on line! http://www.mfjenterprises.com/MFJ-259Bcalibration.php http://www.mfjenterprises.com/man/pd...alibration.pdf I don't see anything other than "watch the blinking SWR" .(sounds like a British insult) for the Advance 3 "calibration". The MFJ-269 had to go back after the review (which itself was a few years ago) so unfortunately I'm no longer able to check your findings, Steve. But don't recalibrate it yet, because that would be stirring-in additional variables which will muddy the waters right now. After the present question has been resolved, you may be able to give the calibration procedure a little more TLC than there was time for on the production-line - but you'll need some precision standards to do it. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek The problem is the I found nothing wrong when measuring in all the other modes. Only this one problem and I believe this is a calculation in the microprocessor, not anything that can be "calibrated" to correct. I was asking if this is correct. I also see nothing in the MFJ cal procedure for the 269 for this mode other than "watch the blinkin' SWR symbol" (I indicates you have set a Zo other than 50. -- Steve N, K,9;d, c. i My email has no u's. |
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