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Has anyone experienced excessive RF radiation from their MFJ-998. When I run a signal (any mode) on 80m more than 70 W? through the tuner I have adverse effects from several devices including my oven, computer monitor and remote controlled lights, all devices have RF chokes on them. When I bypass the tuner I do not have the same issues.

The obvious questions that spring to mind are:
Is it and the rest of your equipment well grounded, with a separate wires going to a common bus bar, that includes the transmitter and all your other equipment?
When you say you bypass the 998, is that switching into bypass or physically removing it from your system?

I have an MFJ 998, but have not installed it into my system yet, (currently using an MFJ 962 manual tuner) so will be interested in what you find out when you resolve the problem.?
Hope you find that it is something simple to fix and not an inherent design problem.
--
Jeff - NZ2S

Hi Jeff,
Thanks for the reply.
Some answers to your questions. Yes each major piece is grounded to a common ground separately . I have and RSP DUo and 2 TX/RX switches that are not grounded separately, my next test I'll remove them and run direct to antenna. from the tuner.
To bypass the 998 you can manually bypass it so it routes directly to the antenna (or power it down). I do this when I'm on a resonant spot on the 80m dipole 3.752 mhz where the SWR is 1:1 and a tuner is not needed. When transmitting 100W from my Yeasu ft-991 I don't have the same apparent RF interaction. I have tried using an SDR to see if there is a resonant Frequency that appears only when using the 998, but it wasn't obvious if it's there.
Interestingly enough I replaced an MFJ-962 with the 998 and I don't recall having this issue (after I installed some RF chokes on the lights and Oven)
I do find the 998 so much easier to use than the 962 and hope I can isolate the issue, meanwhile I refrain from the 80 m band
73 Mick VA3EPM

I have FTDX101D, MFJ998 combination.
All independently grounded to external earth via a copper busbar.?
I experience no RF in the shack so I doubt it is a design fault in the 998.
GL sorting it
Garry

Hi Mick,
Given Gary's experience with the same combo as you and your comment that you didn't experience it with the 962 after you installed "some RF chokes on the lights and oven", it would be my guess that you have one coax cable in your chain that has a poor ground connection.
I experienced a similar problem until I found the offending coax, every connection in the transmission chain is a potential offender. Interestingly enough it physically appeared OK, but obviously was not making a good connection. So you might try swapping out some coax's for better coax's and see.
?Since the Chinese so239/pl259's are so sloppy, I have removed any that I once had from my system, and in fact and switching as much of the connectors over to "N" connectors as I can, this over course means even getting Into some equipment like the tuners and switching the SO239 for a an "N", they are just a better connector.
--
Jeff - NZ2S

Garry, Jeff,
Again thanks for the feedback.
I decided to start eliminating all possible sources, so I removed the tuner, still an issue (thankfully because I like my 998) then bypassed all accessories (one by one including cables) and directly routed the output of my FT-991a to my antenna (still a problem) but there is a coax coupling in the line (to the antenna) so I checked that, it was a little loose. After tightening it the problem was gone, So I tightened some more (with pliers) and the problem is back.
I do think it is the source, I doesn't look "clean" , I'm going to cut the connector off and replace it until I have time to replace the cable with one that is long enough to not need a coupling. I have a new roll of M&P Airborne 10 calling out "Use Me"?
So I think Jeff you were correct in your assessment. When I finally replace it I'll post again hopefully with my success.
73
Mick VA3EPM

Mick . . .

On Thu, 04 Apr 2024 11:02:52 -0700, "Mick" <Va3epm@...> wrote:

. . . so I checked that, it was a little loose. After tightening it the problem was gone, So I tightened some more (with pliers) and the problem is back.

Sounds like you found the intermittent fault. I wonder if you hadn't tightened
it some more if you might have thought the problem was a simple tightening
problem and later on had the same problem reappear?

So you'll get to use some of your M&P Airborne 10 now. :-)


Donald KX8K



----------------------------------------------------
Some ham radio groups you may be interested in:
/g/ICOM /g/Ham-Antennas
/g/HamRadioHelp /g/Baofeng
/g/CHIRP

Hi Donald,
Yes, I expect that if I hadn't retighten it the RF would have re-appered. At the time I had hand tightened it and knew it was loose. I figured with pliers and a really good tighten the problem is permanently gone... not the case and I'm glad it failed this way. I've since cut off the connector and replaced it, There now seems to be no RF issues, and the old connector ground was corroded and didn't seem to have a proper ground connection. The Airporne 10 cable is still in the plan but it's waiting for a new beam antenna. I'm thinking of replacing my Alpha delta DXCC dipole with an MA6B mini yagi. not 100% sure that's what I'm going to do yet. I am limited to a roof top antenna and the MA6B is about as big as I can go. I even think a hex beam is more that what would be acceptable.
73 Mick VA3EPM

Don't know when you posted you problem, But I have a MFJ-986 whish has a similar problem.
I normally work 80 mtrs so have not noticed it on other bands. I run it with a Heathkit Warrior HA10 usually about 500watts.
I noticed it causes my computer to freeze when using a websdr KFS in Half Moon Bay CA. Also my HP Office Jet printer comes alive and starts selecting different menus. With the amplifer not keyed but still passing RF thru the tuner it messes with the printer occationally. With everything staying the same except removing the MFJ-986 tuner and putting my Heathki SA-2040 tuner in place there is no interference. grounding does not change anything with either tuner. Recap... MFJ-986 500 watts interference, Heathkit SA-2040 no interference. I am using ladder line to feed the antenna. Both tuners give same SWR. ?Any suggestions besides connectors?
Thanks, Ken N6BSS

Ken,
After I replaced the coax connector ( which did make a difference) I added several Ferrite Mix 31 snap-ons from Palomar Eng. I think all issues were resolved after a few were added but I know all issues are resolved now.
I suspect the reason it was more noticeable after I started using the MFJ-998 is because I get a better tune with the MFJ-998 and can TX at a higher power than before.

73 Mick VA3EPM