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| Reviews Summary for MFJ 912 4:1 W9INN Balun Box |
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Reviews: 13
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Average rating: 4.4/5
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MSRP: $69.95
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Description: Use coax from antenna tuner to MFJ-912 mounted outside. MFJ-912 converts unbalanced coax to balanced transmission line (ladder).
Giant 2-core 4:1 balun wound with Teflon wire connects to high voltage ceramic feedthru insulators.
Handles full legal limit with ease. SO-239 connector.
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More info: http://www.mfjenterprises.com/products.php?prodid=MFJ-912
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K6XR
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Rating: 5/5
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Feb 12, 2006 07:00
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Grounds the system
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Time owned: more than 12 months
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I have used the w9inn balun for several years and I have spoken personally to w9inn (he has passed on)and he explained to me that he designed the balun and gave the rights to MFJ. He stated that it was a voltage balun and that when grounded from the ground lug, it grounded the whole system. that is the only ground I use and it works fine with 450 ohm ladder line to an EDZ for 20 meters. I use both a manual tuner, the mfj 986, the mfj 974hb, the mfj-993, and elecraft T1 with it and no problems with any of them. The Balun works well. I compared it with the Radio works current remote balun and could tell no difference in performance.
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AC0DV
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Rating: 4/5
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Feb 12, 2006 03:01
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Got rid of RFI
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Time owned: 0 to 3 months
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Just installed this balun for a 290' full wave horizontal loop. (Loop Skywire)
I have a "voltage" balun inside my MFJ 949E tuner... for balanced line.. but I got RFI when using it... and everything I read says a current balun is better... so I opted for this balun and 10-15' of coax from outside my window to the rig. (And it's heavier duty than the tiny balun inside the tuner.)
Seems to work great... although I moved it today and put it into a plastic container since it's not waterproofed.
Concerning the ground lug... I'm not sure what the manual or the last reviewer was saying... the manual says: "Both sides of the balanced line have a continuity to ground so grounding the box will ground the system".
The last reviewer says:
"There is a ground nut on the Balun wich makes is possible to ground the whole antenna system from that point - but i did not -i diddent want my coax to be the direct carrier of ground currents from the tuner and rig, so i gounded the rig instead. IÂŽam very satisfied and recommend it."
What is the difference? What does he mean by "ground currents from the tuner and rig"?
From the rig the coax should be grounded... no? And so the ground would be through the coax up to the balun? So if you ground at both points is that not BETTER? Better RFI reduction?
Or am I missing something about "grounding the system?"
--Keith -- AC0DV
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OZ1HTH
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Rating: 5/5
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Nov 9, 2004 01:20
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Does the job
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Time owned: 0 to 3 months
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I have used the MFJ 912 balun for a month and it does a great job. First of all, its NOT waterproof, and got to be mounted under the roof or where its not exposed direct to rain. I my case that was not a problem (there are holes to fit screws in), its well crafted and specially i like the two big ceramic insulators cause they gives you a very good and safe connection of the ladder line. The coax fits on to the SO239 connector. I have about 4 meters of 50 Ohms coax and 20 meters of US-Wireman 450 Ohms ladderline and in the end of that a 40 meters vertically feed Delta loop, and its working perfectly. No TVI/RFI at all, no matter what band iŽam working on from 40 meters up to 10 meters. No indication of losses is registred, and having a good "ragchew" at full power doesent make the balun warm or changes the SWR.
There is a ground nut on the Balun wich makes is possible to ground the whole antenna system from that point - but i did not -i diddent want my coax to be the direct carrier of ground currents from the tuner and rig, so i gounded the rig instead. IŽam very satisfied and recommend it.
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