Flex 6300 and Mfj-993 Matching problem.

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Flex 6300 and Mfj-993 Matching problem.
I can only get the Mfj-993 to tune up on the 17m band.On all other bands i get no response from the 993.When i first got the Flex 6300 this system worked fine.Any suggestions.Thank you.GM0LZE
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Dolan Morrison

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Posted 2 years ago

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Mark WS7M

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I have one of the MFJ 998 external tuners that behaves in a similar fashion.  I wonder if they use the same "auto" circuitry.

What has worked for me is to power cycle the tuner and it seems that when I do that it will auto-tune but these days I have to do it almost every time I want the thing to tune.
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Mike va3mw

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Can you get the MFJ993 to tune into a dummy load as a test?  That would tell a lot of the story if that works.

How muchy wattage are you using from the 6300 the tuner?  If you have a spare watt meter, you could insert it in between the radio and the tuner to see if the radio is putting out any power.

Can you describe your problem a little better.  We need more details.

mike va3mw
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Jim Gilliam

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Does the tuner allow you to tune manually? That might check to see if the auto tune circuitry is awry.


Jim, K6QE

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Michael Coslo

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Sometimes whne the tuner doesn't seem to be working...

Make certain the slice is in the band we transmit in. I know that sounds like a "duh!" but I've done just that. 

Rest the tuner to factory defaults (C-DN plus  L-DN plus Tune) when turning the tuner on. then press C-Up . 

Do a diagnostic on the unit, Press L1 while turning it on. This will take a little bit to run through, and if it passes, it will say so and send a little bit of MOrse code to say the same.

I've found it important to turn the unit off via the power stitch, not the power supply.

Finally, when turned off it bypasses the tuner and sends the RF directly to the antenna. Anyrhing happening there?
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WX7Y

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Sometime with Auto Tuners your antenna system will be ALMOST there or at a Voltage / Current point that the tuner doesn't like and I have had good luck with adding 10 to 20 feet of coax to the feed-line between the Tuner and the Antenna to get things to tune correctly. 

73's
Bret
WX7Y
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Dolan Morrison

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Thanks for all above replies.On further limited investigation i have reset tuner to factory settings and run and passed the diagnostics test but tuner only matches 17metres ,15m,12m, and 10m.
RF power on tuning i set at 5Watts.
Thank you.Dolan.Gm0lze
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Bob G W1GLV

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5 watts is too low. Most tuners require at least 20 watts.
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Michael Coslo

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5 is marginal on the 993. It will work FB on 10, which is where I have mine st to tune.
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Norm - W7CK

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I have used a couple of the MFJ auto tuners.  The Mfj-993 claims to be able to tune with a minimum of only 2 watts.  Mine will rarely ever do this.  I normally run around 20 watts and it tunes every time.  Keep in mind that most modern day transceivers will fold back power when the swr is high.  It is possible that your Flex is folding back the power to a level that is below the threshold the Mfj-993 requires.

Try bumping up the output on your Flex to 20 watts.
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Michael Coslo

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Quick question Dolan - what is the length of your doublet? also how much ladder line and of what variety. You might want to drop that doublet to take a look at it. I'd try the advice about using more power first. But something has changed, and the tuner is working. 

Also - I'm not certain where to put this, but a ladder line fed tuner can get more consistent tuning between damp/rainy and dry days by occasionally waxing the ladder line. Over time, dirt and or UV/weather degradation can cause the surface of the Ladder line to not shed water like they do when brand new. Sounds weird, but seems to work for me.
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Dolan Morrison

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Hi Michael,i Have actually been using a Hustler 5 band vertical up to this point but today changed the antenna to my off centre dipole.Same problem.The MFJ993 will only  tune up the bands 17,15,12 and 10.On the other bands there is no reponse from the tuner whatsoever.No indication of rf going to the tuner and definatly no noise from the relays  using 2 watts or 20 watts.Its got me beat.
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Dolan Morrison

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Dear Michael,You are right.Just put a watt meter between radio and tuner and there is no power output on the bands 20,30,40,80 but there is on 160,17,15,12 and 10.
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Mike va3mw

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Make sure you are on the right port for the other bands.  I assume you are using Ant 1 for all cases.
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Dolan Morrison

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Similar results using the internal tuner.
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Tim - W4TME, Customer Experience Manager

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Revert to the lowest common denominator. Reset to factory defaults and test using TUNE to verify that you have power out on all bands.  Also, do not connect the radio to third-party applications that can instruct the radio to do things that you are not aware of while testing.  If you still have issues, open a HelpDesk support ticket.
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Mike va3mw

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Like Tim said.  :)  Dolan, have you  made sure that all bands are using the same antenna port?  Let's start with Antenna 1.
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Dolan Morrison

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Bingo!Without noticing i was using Ant2(Should be Ant1) for the bands that didnt match.Thank you so much all you guys.Great community here.So many things to remember when one gets older.Many thanks again all of the above guys,
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Michael Coslo

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Awesome! As Roseanne Roseannadanna said, "Its always something!"

And don't feel dumb about it - That's MY job....
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Mike va3mw

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Official Response
It doesn't sound like you are getting any RF out on those bands.  Are you sure you are on the right antenna port?  Do you have watt meter you can add between the radio and the tuner?

Mike va3mw

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