Re: [Repeater-Builder] Which Antenna Analyzer?
The MFJ analyzers have very limited use around an RF active site. Any RF picked up by the antenna being checked will interfere with the readings on the analyzer. I even had problems recently trying to check the SWR on a horizontal loop antenna for HF, when a high power AM broadcasting station about 5 miles away was on the air. RF picked up by the loop prevented the analyzer from reading the SWR. The only reliable way I know is a Bird 43 and a transmitter to check the SWR. Even then you have to avoid using the low power slugs as the RF picked up by the antenna from nearby transmitters will cause an error in checking the performance of the antenna under test. 73 - Jim W5ZIT --- On Sun, 1/31/10, John Transue jtran...@cox.net wrote: From: John Transue jtran...@cox.net Subject: [Repeater-Builder] Which Antenna Analyzer? To: Repeater-Builder@yahoogroups.com Date: Sunday, January 31, 2010, 10:26 AM I would like to have an antenna analyzer. The most common with hams seems to be the MFJ analyzers, but I am not a fan of MFJ. So, what do you all use? I'd like the analyzer to cover HF through ham UHF. It would be nice to have it tell me the sign of the reactance, but I guess this can be easily inferred by varying the frequency around the resonance. Thanks in advance for your views and experience. John
RE: [Repeater-Builder] Which Antenna Analyzer?
Eric and Jim, Thanks for your thoughtful replies. Yes, Jim, I have run into the very problem you point out. I live within a mile of an AM broadcast station. Trying to use the MFJ analyzer proved fruitless. But your suggestion to use the Bird and a transmitter has a drawback too. If you are searching over frequency to locate the minimum SWR, and if you have not come pretty close to the right length wire in the first guess, then you will want to search out of the ham band, and this is a no-no except at very low power (as with an analyzer). So, cut and try by paring the antenna length a bit at a time seems to be the only solution (other than moving a few miles away from any broadcast station). Eric, do you think there is any hope that the AEA analyzer would work a mile from an AM broadcast station? I don't know the power of the station, probably in the 5 to 10 thousand watt range I would guess. Advice from anyone else would also be welcomed. John -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jim Brown Sent: Monday, February 01, 2010 10:05 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Which Antenna Analyzer? The MFJ analyzers have very limited use around an RF active site. Any RF picked up by the antenna being checked will interfere with the readings on the analyzer. I even had problems recently trying to check the SWR on a horizontal loop antenna for HF, when a high power AM broadcasting station about 5 miles away was on the air. RF picked up by the loop prevented the analyzer from reading the SWR. The only reliable way I know is a Bird 43 and a transmitter to check the SWR. Even then you have to avoid using the low power slugs as the RF picked up by the antenna from nearby transmitters will cause an error in checking the performance of the antenna under test. 73 - Jim W5ZIT --- On Sun, 1/31/10, John Transue jtran...@cox.net wrote: From: John Transue jtran...@cox.net Subject: [Repeater-Builder] Which Antenna Analyzer? To: Repeater-Builder@yahoogroups.com Date: Sunday, January 31, 2010, 10:26 AM I would like to have an antenna analyzer. The most common with hams seems to be the MFJ analyzers, but I am not a fan of MFJ. So, what do you all use? I'd like the analyzer to cover HF through ham UHF. It would be nice to have it tell me the sign of the reactance, but I guess this can be easily inferred by varying the frequency around the resonance. Thanks in advance for your views and experience. John
RE: [Repeater-Builder] Which Antenna Analyzer?
John, I think you're setting your sights too high. There are excellent analyzers for HF through low VHF, and excellent analyzers for VHF through UHF, but very few that cover HF through UHF. I once tried the MFJ-269, but gave up on it after the THIRD unit died. The first unit had a defective switch, and it was replaced under warranty. The second unit had an improperly-threaded RF connector, so it was replaced under warranty. The third unit was okay when received, but the UHF section died after about three weeks of use. I complained to the MFJ customer service people, and sent the unit back and received a full refund, including the cost of shipping all three units. The sloppy solder joints and haphazard component placement suggests that the assembly was performed by poorly-trained people. Quality control is not one of MFJ's strong suits! Like you, I want to see more detail in the antenna analysis, so I decided to spring for a VIA Vector Impedance Analyzer made by AEA/Tempo. Definitely not cheap, but it does everything I could ask for, including the ability to display results and plots on a computer. It covers 100 kHz to 54 MHz. I was already familiar with this brand, since I had purchased a 140-525 MHz analyzer a year earlier. Although my experience with antenna analyzers is limited to just MFJ and AEA/Tempo, I know that there are other brands available with similar features. Perhaps some commercial test equipment makers offer portable analyzers that will cover HF through UHF, but instruments in the Site-Master class cost many thousands of dollars. Choose wisely... 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of John Transue Sent: Sunday, January 31, 2010 8:26 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Which Antenna Analyzer? I would like to have an antenna analyzer. The most common with hams seems to be the MFJ analyzers, but I am not a fan of MFJ. So, what do you all use? I'd like the analyzer to cover HF through ham UHF. It would be nice to have it tell me the sign of the reactance, but I guess this can be easily inferred by varying the frequency around the resonance. Thanks in advance for your views and experience. John
