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Author Topic: MFJ-914 Auto tuner expander  (Read 21996 times)
K2OWK
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Posts: 1279




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« Reply #15 on: March 07, 2011, 03:54:33 PM »

Hello all, Well I bought an MFJ-914 extender and it does not work for me at all. I am going to call MFJ tomorrow and see whats what. I have a Yaesu FT-450AT. I have three inverted "V" antennas. one on 40 meters one on 10 meters and one on 6 meters. The 40 meter antenna tunes well on 15 using the 450s internal tuner. I installed the 914 as per the instructions. I set the FT-450 to 10 watts out. Using the 40 meter antenna I tried to get it within the tuning range of the 450s autotuner on 20 meters, but was not able to. I tried the same on 80 meters with no luck. The MFJ-949E manual tuner had no trouble tuning these bands with the 40 meter antenna. I read the reviews on the 914 and most said it worked as it should. It just seams it will not tune the 40 meter antenna to within the 450s 3 to 1 tuning range. The 40 meter inverted "V" has a 1.3 to 1 SWR on 40 meters and a 1.5 to 1 SWR on 15 meters without the autotuner engaged. With it engaged it brings it to 1 to 1. The 914 sheet says that it will bring most antennas down to the 3 to 1 SWR required by most autotuners. The 40 meter antenna reads about 6 to 1 on 20 meters and about 8 to 1 on 80 meters. This should be in the range of the 914 which says it can handle a mismatch of 10 to 1. The SWR meter, both the external one and the internal one do not move when the 914 is switched. It actually makes it worse when you try to tune it on the antennas set frequency of 40 meters. I can not get it to reach the 1.3 to 1 that the antenna is trimmed to without a tuner. Does anyone out there have any information as to what the problem could be? I opened the 914 case and the inside looks well made with no cold solder joints.

Thanks,
Regards,
Barry K2OWK
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KH6AQ
Member

Posts: 7892




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« Reply #16 on: March 08, 2011, 12:04:41 PM »

Your problem description is hard to follow. You're jumping all over the place. I can follow but it is tortuous. You talk about three inverted-vee antennas, the 914, then the 949, then you say the 914 does nothing, then you say it makes things worse.

Try rewriting this, perhaps in bullet form. And remove all extraneous information, for example, remove the information about the 6 meter and the 10 meter inverted-vee antennas and the MFJ-949.

Tuning a 40 meter dipole on 80 meters with open line is not good. With coax it's very bad. Tuning it on 20 meters with open line is bad enough. With coax it's very bad.
« Last Edit: March 08, 2011, 12:14:51 PM by WX7G » Logged
K2OWK
Member

Posts: 1279




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« Reply #17 on: March 08, 2011, 12:47:00 PM »

Sorry about the hard to read forum. I was trying to convey to much information at once. I am trying to tune a 40 meter inverted "V" on 80 meters and 20 meters using an MFJ-914 Auto tuner Extender. It will not work. It does not bring the VSWR down low enough for the Autotuner in my FT-450AT to autotune. It requires a 3 to 1 VSWR. Is this beyond the 914s tuning capacity.

I was able to tune this 40 meter inverted "V" on 80 and 40 meters using a manual MFJ- 949E antenna tuner.

Is this any clearer. I hope it is. I am going to call MFJ today to see if they have an answer.

Regards,
Barry K2OWK
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KB4QAA
Member

Posts: 3339




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« Reply #18 on: March 10, 2011, 09:58:46 PM »

Attempting to tune an antenna below it's resonant frequency (i.e. 40m ant on 80m) causes very high voltages and most rig tuners can't do it, and even manual tuners may balk or suffer arcing.
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KA0HCP, ex-KB4QAA Relocated to Ks. April 2019.
K2OWK
Member

Posts: 1279




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« Reply #19 on: March 10, 2011, 10:39:29 PM »

Last note, I learned to use the 914 as it should be used. It works well tuning the 40 meter antenna on 20, 17, 12 and 10. It does not tune all the available frequencies on all the bands, but will tune most. I made some excellent contacts on 20 meters the other day using the 914 with my FT=450s internal auto-tuner and the 40 meter antenna. The antennas SWR on this frequency was 6 to 1. The 914 brought it down to 2.5 to 1 and the auto-tuner in the 450 got to an indicated 1.2 to 1. on the 450s SWR meter. I am sure it will work as it should on the S9 antenna, when the S9 is properly installed with a ground radial system and a 4 to 1 UN-UN at its feed point.

I will let this forum know in the future how it works when I get the antenna installed.

Thanks for all the information I have received.

Regards,
73s
Barry K2OWK
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