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Antenna impedance analyzer comparison
Hi - I am looking for an impedance analyzer. Primarily for antenna
measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) At first glance I have the following points/questions: - Does MFJ-269 offer anything over 259B in addition to VHF/UHF? - W8WWV tests (web) don't indicate that AEA VIA performs better than the MFJs. - Micro908 is new. Any experiences, comments on impedance accuracy? - N2PK may be the most accurate(?) but needs a PC and involved construction. - Any comments on the Autek? All suggestions are appreciated, based on experience and technical quality. 73s de Kristinn, TF3KX |
I have the Autek RF1 and enjoy it a lot. My only comment is that
battery consumption is probably more of an issue than people realize. I feel sorry for those with an analyser that uses a lot of batteries. My Autek is small and power consumption is low, but even then, replacing the single 9v battery is a pain because it always fails when I'm somewhere up in the air!. |
I've used an Autek VA1 for a few years. Carried it on a
sailboat to the Bahamas (in a plastic sack). No problems with it at all. I unplug the battery when it is not in use. The VA1 is a very useful piece of equipment. My opinion of Autek construction and documentation, however, is that it makes MFJ look good. 73, Chuck |
"Kristinn Andersen, TF3KX" wrote in message om... Hi - I am looking for an impedance analyzer. Primarily for antenna measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) Comparing the N2PK VNA to the others is not quite fair as it is in a league by itself- like comparing a go cart to a BMW. Dale W4OP |
On Fri, 31 Dec 2004 20:52:10 GMT, Dale Parfitt wrote:
"Kristinn Andersen, TF3KX" wrote in message om... Hi - I am looking for an impedance analyzer. Primarily for antenna measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) Comparing the N2PK VNA to the others is not quite fair as it is in a league by itself- like comparing a go cart to a BMW. Maybe not a league of its own--for another VNA (not out yet, but hopefully soon), see http://www.tapr.org. |
"Bob Nielsen" wrote in message ... On Fri, 31 Dec 2004 20:52:10 GMT, Dale Parfitt wrote: "Kristinn Andersen, TF3KX" wrote in message om... Hi - I am looking for an impedance analyzer. Primarily for antenna measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) Comparing the N2PK VNA to the others is not quite fair as it is in a league by itself- like comparing a go cart to a BMW. Maybe not a league of its own--for another VNA (not out yet, but hopefully soon), see http://www.tapr.org. I looked at this at Dayton- from memory, I seem to recall the dynamic range was nowhere close to Paul's design and software at that time was rather crude. I'll look again, but for the price, Paul's design is hard to beat- accuracy right up there with the Agilent 40 Gigabuck units. Dale W4OP |
Kristinn Andersen, TF3KX wrote:
Hi - I am looking for an impedance analyzer. Primarily for antenna measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) At first glance I have the following points/questions: - Does MFJ-269 offer anything over 259B in addition to VHF/UHF? - W8WWV tests (web) don't indicate that AEA VIA performs better than the MFJs. - Micro908 is new. Any experiences, comments on impedance accuracy? - N2PK may be the most accurate(?) but needs a PC and involved construction. - Any comments on the Autek? All suggestions are appreciated, based on experience and technical quality. 73s de Kristinn, TF3KX I have used three of these MFJ-259B - OK while it was working, but it has failed twice. I do not recommend! Autek VA1 - Nice - but fiddley to use build quality not good eats batteries! AEA VIA - Very nice, the display makes on-site adjustments and checks easy, ability to store and transfer data to a PC is useful Solid build - won't run off NICAD/NIMH - it needs 12V! N.B. I find the third party PC software better than the official AEA software 73's Stephen G8LYB |
Stephen Tompsett wrote:
Kristinn Andersen, TF3KX wrote: Hi - I am looking for an impedance analyzer. Primarily for antenna measurements (only 1,8-30 MHz) and secondarily for misc. lab measurements (L,C,Q measurements, signal generation, etc.). The possibilities I have been looking at are (in no particular order, prices approximate): a) MFJ-259B ($300) b) MFJ-269 ($220) c) AEA VIA ($600) d) Autek VA1 ($200) d) Micro908 kit from AmQRP ($210) e) N2PK Vector Network Analyzer project ($150) At first glance I have the following points/questions: - Does MFJ-269 offer anything over 259B in addition to VHF/UHF? - W8WWV tests (web) don't indicate that AEA VIA performs better than the MFJs. - Micro908 is new. Any experiences, comments on impedance accuracy? - N2PK may be the most accurate(?) but needs a PC and involved construction. - Any comments on the Autek? All suggestions are appreciated, based on experience and technical quality. 73s de Kristinn, TF3KX I have used three of these MFJ-259B - OK while it was working, but it has failed twice. I do not recommend! Autek VA1 - Nice - but fiddley to use build quality not good eats batteries! AEA VIA - Very nice, the display makes on-site adjustments and checks easy, ability to store and transfer data to a PC is useful Solid build - won't run off NICAD/NIMH - it needs 12V! N.B. I find the third party PC software better than the official AEA software At the time I attempted to review the AEA-CIA a few years ago, my worry was with the built-in firmware, which produced weird results in R-X mode (like, physically impossible). The difference between the "amateur" and "professional" leagues for impedance measurement is that the professional Vector Network Analysers use a calibration procedure to compensate for their own internal errors. This boosts the measurement accuracy into a completely different league. Of all the ones mentioned, only the N2PK and the TAPR designs can do this. All the others really are playing in the amateur league. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
The N2PK would be the best, except that it only runs when
connected to a laptop. I don't have a laptop, and if I did, I wouldn't want to carry it out to the antennas, and furthermore, laptop displays are usually not visible outdoors during daylight. All the others don't work if you have nearby AM BCB stations like I do. Still looking for an antenna analyzer I can really use. Rick N6RK |
Dear Rick, N6RK:
If you believe that none of the "other" analyzers will work at your site because of the presence of strong signals from below 1700 kHz, then you could do one of the following: 1. You could build a high-pass filter to go between analyzer and antenna to attenuate the MF signals. I have heard of people doing this successfully such that the filter is essentially transparent at HF. 2. You could add one or more band stop resonators that can be tuned to number 1 and really cut down the one or two most strong broadcast signals. 3. You could search for a used or new bridge type of instrument. They tend to be insensitive to off-frequency signals. 4. Many types of antennas will deliver little of a signal that is far away in frequency. An inverted L is expected to deliver a lot of signal from nearby MF stations. A balanced LPDA with a shorting strap at its far end is expected to pick up little from vertically polarized MF stations. Let the group know what type of antennas you wish to analyze. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Rick Karlquist N6RK" wrote in message news:cS4Cd.611717$wV.601406@attbi_s54... The N2PK would be the best, except that it only runs when connected to a laptop. I don't have a laptop, and if I did, I wouldn't want to carry it out to the antennas, and furthermore, laptop displays are usually not visible outdoors during daylight. All the others don't work if you have nearby AM BCB stations like I do. Still looking for an antenna analyzer I can really use. Rick N6RK |
"Rick Karlquist N6RK" wrote in message news:cS4Cd.611717$wV.601406@attbi_s54... The N2PK would be the best, except that it only runs when connected to a laptop. I don't have a laptop, and if I did, I wouldn't want to carry it out to the antennas, and furthermore, laptop displays are usually not visible outdoors during daylight. All the others don't work if you have nearby AM BCB stations like I do. Still looking for an antenna analyzer I can really use. Rick N6RK Rick, you don't HAVE to use a laptop, or carry it to the antenna or worry about being able to see the LCD. Simply take your N2PK, couple it to the feedline in the shack, (and your desktop computer) do the OSL calibration out at the antenna end of the feedline and measure the antenna from the comfort of your operating position. You've just calibrated out the feedline. You can REALLY use the VNA. Regards W4ZCB |
"J. Mc Laughlin" wrote in message ... Dear Rick, N6RK: If you believe that none of the "other" analyzers will work at your site because of the presence of strong signals from below 1700 kHz, then you could do one of the following: 1. You could build a high-pass filter to go between analyzer and antenna to attenuate the MF signals. I have heard of people doing this successfully such that the filter is essentially transparent at HF. The filter needs to have no group delay in the band of measurement (not just flat group delay and amplitude). It is impossible to build a high pass filter with no group delay. 2. You could add one or more band stop resonators that can be tuned to number 1 and really cut down the one or two most strong broadcast signals. Too much trouble. 3. You could search for a used or new bridge type of instrument. They tend to be insensitive to off-frequency signals. I have a GR-916 bridge if I really must make a measurement. 4. Many types of antennas will deliver little of a signal that is far away in frequency. An inverted L is expected to deliver a lot of signal from nearby MF stations. A balanced LPDA with a shorting strap at its far end is expected to pick up little from vertically polarized MF stations. Let the group know what type of antennas you wish to analyze. I have a 90 foot vertical for 160 meters. I use it because it gets out very well. Unfortunately, it is also a good BCB receive antenna, developing nearly a volt of RF. Rick N6RK 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Rick Karlquist N6RK" wrote in message news:cS4Cd.611717$wV.601406@attbi_s54... The N2PK would be the best, except that it only runs when connected to a laptop. I don't have a laptop, and if I did, I wouldn't want to carry it out to the antennas, and furthermore, laptop displays are usually not visible outdoors during daylight. All the others don't work if you have nearby AM BCB stations like I do. Still looking for an antenna analyzer I can really use. Rick N6RK |
Rick Karlquist N6RK wrote:
1. You could build a high-pass filter to go between analyzer and antenna to attenuate the MF signals. I have heard of people doing this successfully such that the filter is essentially transparent at HF. The filter needs to have no group delay in the band of measurement (not just flat group delay and amplitude). It is impossible to build a high pass filter with no group delay. [...] I have a 90 foot vertical for 160 meters. I use it because it gets out very well. Unfortunately, it is also a good BCB receive antenna, developing nearly a volt of RF. Any impedance/network analyser is going to need a BCB-reject filter in order to handle that level of interference. However, imperfections in the filter don't matter with a more advanced VNA such as the N2PK design, because the filter can be included *inside* the calibration loop. As Harold W4ZCB says, a long coax can be included inside the calibration loop as well, so you could make the measurements from home... in principle. But you'd have to do a lot of shuttling back and forth between the shack and the antenna to swap connectors, start the VNA etc. At Rick's QTH (www.n6rk.com) that would involve a *lot* of travelling time. Seriously, Rick, if the lack of a laptop is all that's stopping you... then get a laptop already! (Almost any old wreck will run an N2PK VNA.) Add an awning, a camping table, chair and cooler, and you're all set for accurate impedance measurements in the field. I'm going to be doing a lot of that in the next two years, but the environmental problems will be slightly different. Where can I find a laptop with a screen demister and two-speed wipers? -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Any impedance/network analyser is going to need a BCB-reject filter in order to handle that level of interference. However, imperfections in the filter don't matter with a more advanced VNA such as the N2PK design, because the filter can be included *inside* the calibration loop. GM Ian, Actually, I have used the N2PK under the same conditions that Rick has and you DON'T need the reject filter. That volt is an aggregate number and at any 2-3 Hz bandwidth that the VNA detector is looking at, it's at the uVolt level and not a bother. (Unless you tune TO the BC signal itself of course!) As for the walk, would probably do most of us some good, but I even substituted the guy that wanted the measurements made and a pair of $5. FRS radios for the walk. Works fine if you really want to measure the antenna. Rick can put the feedline, his transformers and the kitchen sink inside the cal loop and still measure his antenna if he REALLY wanted to use it. Used Laptops with a parallel port (And worn out battery) are running 25-50 bucks around here. Had one given to me that Alice plays the cardgame with using the charger. Most will still hold a charge for an hour or so. I'm going to be doing a lot of that in the next two years, but the environmental problems will be slightly different. Where can I find a laptop with a screen demister and two-speed wipers? Try a portable igloo, Rain-X doesn't work very well. Regards W4ZCB |
Dear Rick:
OK. Your vertical antenna certainly picks up a lot of stray RF. However, one of the beauties of using a network analyzer is the ability to characterize the transmission line (even 1000 feet of it) and a filter that is between the network analyzer and the antenna, AND THEN to have the effects of all of the stuff between the analyzer and antenna removed so as to leave the properties of the antenna. One has to measure the "stuff" (transmission line +) with the "stuff" disconnected from the antenna. Even if you went out to the antenna, you would need (temporarily) to disconnect the "stuff" from the antenna. This scheme really works. One has some front-end-load required in order to characterize the "stuff," but then it is straight forward. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: |
I had a laptop a long time ago, and I couldn't
read the screen outdoors. Are the newer ones better? Rick N6RK "Ian White, G3SEK" wrote in message ... Rick Karlquist N6RK wrote: Add an awning, a camping table, chair and cooler, and you're all set for accurate impedance measurements in the field. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Rick Karlquist N6RK wrote:
I had a laptop a long time ago, and I couldn't read the screen outdoors. Are the newer ones better? If the LCD that you remember was an old passive matrix type, you may be pleasantly surprised by a modern active matrix (TFT) display. LCDs are still not as bright as a CRT, though, so I was more than half-serious in suggesting an awning for shade. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
But I want to adjust the matching network at the base
of the antenna. I need real time feedback to when I turn a know. An indicator 1000 ft away is useless. Rick N6RK "J. Mc Laughlin" wrote in message ... Dear Rick: OK. Your vertical antenna certainly picks up a lot of stray RF. However, one of the beauties of using a network analyzer is the ability to characterize the transmission line (even 1000 feet of it) and a filter that is between the network analyzer and the antenna, AND THEN to have the effects of all of the stuff between the analyzer and antenna removed so as to leave the properties of the antenna. One has to measure the "stuff" (transmission line +) with the "stuff" disconnected from the antenna. Even if you went out to the antenna, you would need (temporarily) to disconnect the "stuff" from the antenna. This scheme really works. One has some front-end-load required in order to characterize the "stuff," but then it is straight forward. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: |
Rick Karlquist N6RK wrote:
My old laptop was an active matrix, and it still wasn't readable in sunlight, or even in a room on a sunny day near a window. I have the same problem with my IC-756PRO. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
My old laptop was an active matrix, and it still wasn't
readable in sunlight, or even in a room on a sunny day near a window. Rick N6RK "Ian White, G3SEK" wrote in message ... Rick Karlquist N6RK wrote: I had a laptop a long time ago, and I couldn't read the screen outdoors. Are the newer ones better? If the LCD that you remember was an old passive matrix type, you may be pleasantly surprised by a modern active matrix (TFT) display. LCDs are still not as bright as a CRT, though, so I was more than half-serious in suggesting an awning for shade. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Dear Rick:
I missed your response of some days ago. Now I understand the actual issue. When I feel like it, I have a manually adjustable vacuum variable capacitor that I use to shunt feed a tall tower for 160 meters. The "tap" is such that the real part of the impedance is about 50 ohms and the capacitor cancels the inductive part of the impedance. I use an AEA CIA right at the capacitor to find the right adjustment and then connect the Heliax. In your case, a partner at the base might make small adjustments while you radio back what you wish for him/her to do next. Do let us all know the solution you find. Good luck. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Rick Karlquist N6RK" wrote in message ... But I want to adjust the matching network at the base of the antenna. I need real time feedback to when I turn a know. An indicator 1000 ft away is useless. Rick N6RK |
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