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Author Topic: AL-80B, MFJ-998, FT-857 Connections  (Read 3535 times)

Posts: 24

« on: November 25, 2012, 05:09:58 AM »


Not sure which forum to put this in... I'm using an FT-857 as a base and just ordered an AL-80B amp and MFJ-998 tuner. Trying to understand the connections between all 3.

I have a CT-62 currently going from the FT-857 Cat/Linear to my PC Serial Port for HRD and it works great. Based on research, it looks like I need to:

* Splice in an RCA plug to the CT-62 to go to the MFJ-998 Amp Enable In.
* Go from the MFJ-998 Amp Enable Out to the Al-80B RLY.
* For ALC control I would need to go from the AL-80B ALC to the FT-857 ACC

This should allow me to take advantage of the MFJ-998 Amp Disable feature while tuning and also do the automatic ALC option.

Assuming this is right so far, I don't know if I need to do anything with the MFJ-998 Radio Interface port which would normally connect to the FT-857 CAT/Linear.

I've called both Ameritron and MFJ and didn't really get clear direction. I do have a cord that would go between CAT/Linear and the MFJ-998 Radio Interface but not sure if I need it or how I would splice it and the CT-62 together. Not sure how the Radio Interface and the Amp Enable In relate to each other on the MFJ-998.

Thanks in advance for your help!!!


Posts: 1556

« Reply #1 on: November 25, 2012, 05:18:24 AM »

You can do this as you've suggested (no MFJ-998 radio interface cable).  I did something similar with  my Elecraft K3 as there was no radio interface available for that radio.  I'd leave the MFJ-998 in AUTO.  Then to tune, I'd transmit a 10-20 watt carrier from the K3 and if the SWR was above the 2:1 (default) start-tuning point, the MFJ-998 would autotune.  And, of course, the amp enable line would be open so the amp would not be on-line while tuning.

The advantage of the radio interface cable is that you can enable tuning by pushing TUNE on the MFJ-998.  That will automatically put your transceiver into a low-power TUNE mode for you.  I did have this capability when I had a Yaesu MarkV as there was a radio interface available for that transceiver.

Phil - AD5X

Posts: 766

« Reply #2 on: November 26, 2012, 06:54:16 AM »

I use MFJ-998 with TT Centurion and 80m dipole fed by ladderline. My experience is that MFJ-998 is moody. It matches many but not all bands with one balun, and it matches fewer bands with "commercial" super balun. In CQ WW SSB, SWR was power dependent so I was forced to turn off sticky tune. In CQ WW CW last weekend everything was perfect.

So before you try to automate, see that it all works manually as MFJ 998 has less tuning range than other tuners and is susceptible to RF in a peculiar way.   

My experiences with other tuners (lower power) were predictable.

Ignacy, NO9E
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