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Reviews Categories | Antenna parts, accessories, incl. baluns, hardware, etc. | MFJ-915 RF Isolator Help

Reviews Summary for MFJ-915 RF Isolator
MFJ-915 RF Isolator Reviews: 25 Average rating: 4.3/5 MSRP: $29.95
Description: 1:1 Current Balun to reduce stray RF on coax.
Product is in production.
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KK4OBI Rating: 2/5 Jun 3, 2019 01:00 Send this review to a friend
Changes antenna frequency  Time owned: 0 to 3 months
The antenna is a home brew version of the MFJ-1790 vertical only for 20 meters. It resonates at 14.3 mHz but, with the MFJ-915 RF isolator attached, it resonates at 15.0 mHz. Unuseable.

A type 43 Guanella or clip-on ferrite chokes were satisfactory and had no effect on tuning.
K4FY Rating: 5/5 May 9, 2019 13:23 Send this review to a friend
Works Well  Time owned: more than 12 months
I don't know the value for common mode isolation is but it is high enough to be effective in stemming common mode currents that may cause RFI. It works well in my OCFD and 4:1 dual core current BALUN. I run 700 watts SSB/CW
VE3TMT Rating: 5/5 Sep 7, 2018 14:40 Send this review to a friend
Solved my RFI Problems  Time owned: 0 to 3 months
Over the years I've been having various RFI issues in the shack that were resolved with ferrites, and other methods. However, two issues I could not resolve were one of the TV's upstairs would mysteriously turn on when I operated on 40m, and my outdoor driveway lights would come on every time I transmitted. For the past couple of months, since acquiring a TenTec Pegasus, I have been plagued with RF in my mic audio. I tried mini mix 31 cores on the mic leads which helped a bit, but didn't totally eliminate the problem. In desperation, I purchased the MFJ-915 line isolator. Installed at the antenna connector of the Pegasus, it has pretty much eliminated the mic RFI, the TV no longer turns on, nor do the driveway lights. It also seems the receiver is quieter than it was before. Not as much noise. I am totally satisfied with the results.
K6EB Rating: 3/5 Jul 5, 2017 12:26 Send this review to a friend
Quality Control  Time owned: 3 to 6 months
It does what it is supposed to do, but I have bought two of them and both times the screws have stripped and fell out after two or three months, and they filled with water in the winter. I'm going to try a different isolator this time around.
W2DL Rating: 5/5 May 22, 2017 11:57 Send this review to a friend
So far, so good  Time owned: 0 to 3 months
I have five dipole antennas in the hemlock canopy on my property. All of them have the Alpha Delta DELTA-C center insulator kits with coax connectors. Because of this, I looked for a balun that had coax connectors on both ends and could be connected to the Alpha Delta DELTA-C center insulator using a uhf double male adapter (Amphenol 83877). The Radiowavz B-11 ISO 1:1 balun does this, so I bought five. Three failed within a year. I've since replaced them with MFJ-915s which also have coax connnectors on both ends. The MFJ-915s appear to be built much better and they cost a hunk less. I plan to replace the remaining Radiowavz with MFJ-915s the next time those antennas require maintenance. If interested, see my review of the radiowavz B-11 ISO 1:1.
KK4GGL Rating: 1/5 Feb 13, 2017 21:38 Send this review to a friend
Poor workmanship  Time owned: 0 to 3 months
I bought 2 isolators directly from MFJ at a hamfest. When I got them home and tried to attach the coax, I found that the PL-259s would not fit on any of the 239s. The holes were off-center preventing the 259 to fully seat.
K6SDW Rating: 5/5 Aug 4, 2016 22:09 Send this review to a friend
2 years going  Time owned: more than 12 months
It works........I know, it's MFJ but really, it's worked for 2 years now
N5TQ Rating: 5/5 Aug 4, 2016 15:28 Send this review to a friend
Works like a charm  Time owned: 0 to 3 months
My solid state amp would trip off on the upper end of 40M despite a 1.1 VSWR. Probably because my coax run is about 40M also! But given my lot and antenna config, I really couldn't shorten it. So I put 2 of these in, one in the coax entry point in my shack, and another one close to where the coax enters the house. Bingo! But it took 2, the one in the shack alone didn't work by itself.
N6CIC Rating: 4/5 May 30, 2016 12:50 Send this review to a friend
Good when needed  Time owned: more than 12 months
When operating at of my antenna restricted house using a shortened loaded vertical (Buddistick) I was getting so much Rf in the shack that my radio would shut down, my keyer gave extra dits, and I could feel tingling on my fingers. I inserted the Rf isolator into the feedline after my tuner and the Rf problems were gone. However, when using a simple dipole cut for the band I was working, I found that the Rf Isolator "detuned" my antenna and my internal as well as external antenna tuners could not bring down the SWR. Removing the Rf Isolator solved that problem. So my conclusions are--it works very well in antenna configurations where needed, but for resonant antennas it may or may not be useful.
WB9OTX Rating: 5/5 Dec 30, 2015 19:22 Send this review to a friend
It did the trick  Time owned: 0 to 3 months
I am running a pair of 1/4 wave phased verticals. It seemed 90 % of the time I would receive lower reports than I gave out when using JT65 digital no matter what power I ran. I installed the MFJ-915 RF Isolator that I got used on QTH. I inserted it at the input of the relay box thinking I would just see if it helped, and did it ever - I now can run from 5 to 20 watts and get now as high or higher reports back. The RF on the feed line must have been throwing the pattern off on transmit. A very cheap fix. I did waterproof the connections with coax seal. I do run 1.5 KW on these antennas with SSB and the choke takes it with no problem. I'm not a big fan of MFJ but this is a winner.
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