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Author Topic: MFJ 998 Tuner Frequency Display changes when transmitting  (Read 1009 times)
K9ATL
Member

Posts: 2




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« on: January 15, 2013, 06:43:30 PM »

My MFJ 998 legal limit Automatic Tuner recently started to change Frequency when I transmit bare foot on a new Kenwood TS-590.  I have owned the tuner for a little over a year and have operated it with an FT-857D and never saw this issue.  The tuner does not re tuned it just displayed various frequencies within the band as I modulate.  In trouble shooting, I removed the Kenwood TS-590 and reconnected the FT-857D and the same issue occurred with the tuner being connected to the FT-857D radio.  Again this has never happened with that radio before.  The tuner is used to  tunes a G5RV Dipole and a DX Engineering Vertical.  Signal reports from several stations indicated that I had a good signal and that I was on frequency even though the display swing-ed radically around.  Finally one station with a flex radio finally indicated I was off frequency slightly with the new TS-590 but the radio displayed that I was dead on on Frequency. The following night I used the TS-590 again with the tuner and requested from other station if I was off frequency. Numerous stations replied that I was one frequency  but the frequency display on the tuner continue to move around rapidly as I transmit at 100 watts with both radios.  Puzzled by what is currently happening does anyone have any ideas ?   
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WB2EOD
Member

Posts: 219




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« Reply #1 on: January 15, 2013, 08:45:54 PM »

I own one of these. This is not a problem. 

When you put out a straight carrier, during tuning for example, the display frequency will be constant and correct. 
Since SSB has no carrier, the frequency at any given instant is somewhat dependent upon the modulation.  It will vary a bit from your rig's dial setting.  This is mentioned in the instruction manual.

If you haven't done so, you should read the instruction manual beyond the "quick start" pages. 

Hope this helps
73
WB2EOD
email to my call at arrl dot net
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VK3TEX
Member

Posts: 8




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« Reply #2 on: January 15, 2013, 08:50:52 PM »

I would check your earth connectin to the atu and then check
All connections to the atu and make sure that any coax
Does not have a loose braid connection to plugs.
Seems to be slight rf feedback getting in to atu somehow.
Make sure the swr on your antennas has not changed.
Loose hardware can do this.
If that don't help try to think of what physical changes
We're made in the shack and try to reverse them and
See how you go. Hope this helps and let us know of your
Solution should you find and fix the problem.
Cheers, Les VK3TEX.
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K9ATL
Member

Posts: 2




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« Reply #3 on: January 16, 2013, 04:41:38 PM »

WB2EOD and VK3TEX.  Thanks so much for the responses to my post on MFJ 998.  good to know I don't have a major issue with the tuner.  The XYL did ask me to rearrange some items in the room where the shack resides so I will look out for RF and change back if needed. Thanks you both for sharing your advice with a fairly new operator....73
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