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Anyone using an MFJ-993B with an MFJ-5124Y interface cable to a Yaesu tranceiver? I have been attempting to get the unit to work correctly. At low power it autotunes correctly; when I increase power the SWR increases so that I have go through the retune process several times. MFJ tech info service is useless and is no help, as expected. Is it just this unit or is it common behavior.

K3YZ

I have a 993B with a Kenwood that had similar problems. I found inside a resistor network on a vertical board at the center rear had a bad solder joint. it was really loose and wobbly.?
It is a real pain to get to it to resolder as I had to disconnect everything at the rear panel including removing the four banana jacks to get clearance to swing the main board up. I left all the front ribbon cables alone.
I resoldered all the blobs on that resistor board while I had it out and that seemed to fix it.
You may want to test it by putting pressure on the resistor board while transmitting to see if it is a bad contact before you tear it down. Use a plastic tuning tool or similar as that area is hot with RF.

Good luck

Dennis N4KPI

Hi Allan,
I have used the 939y and cable with FT 891 with good results. I have not had to retune after going to full power. Once you get it tuned at the higher power does it stay tuned? ?I wonder if there is some component heating up? What kind of antenna? I would try using a dummy load and see what happens. ?

Mike AD0L?

I had a similar problem a Yaesu Mark V Field. It worked ok with low power, but not above around 20 Watts. I found out that it was stray RF. I ran my 600 ladder line differently from the tuner so that the RF was at a 90 degree angle and it works fine at 100 Watts now. I also grounded the rig to the tuner.

73 Richard W4MCD?