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Need some help with MFJ-925 auto tuner ...

May 15th 2012, 19:19

speedmaster

Joined: Apr 18th 2011, 12:20
Total Topics: 0
Total Posts: 0
Hey, guys. I'm a new ham. I got a used Alinco DX-70 setup in my kitchen. I bought a 6m-40m dipole and have it strung outside the kitchen window.

Between the two I have an MFJ 925 antenna tuner ( http://www.mfjenterprises.com/Product.php?productid=MFJ-925 ).

I haven't had much luck getting it to work. Almost every time I attempt to transmit on any HF band it beeps "QRP" back to me in CW, which I think means it wants a lower power.

I can't get the radio to drop to low power so I whisper so that the radio is only pulling a few watts. Then the tuner's green light comes on telling me I think that we have a good tuned SWR.

But when I then go to transmit at full power the tuner starts beeping "QRP" at me in CW again.

I did reset the radio and MFJ tuner to factory settings, but it hasn't helped.

Any ideas?

Thanks very much in advance,
Chris
http://www.pretenseofknowledge.com/
May 16th 2012, 12:50

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

I suggest getting the MFJ-5114A radio interface--according to the MFJ-925 instruction manual, it will allow the user to control the tuner with a simple push of the [TUNE] button on the front panel.

Alternately, if you plan to operate digital modes, it may be practical to use the digital mode setup to send a low power carrier as required by the tuner. It sounds like you are trying to use a weak voice signal to tune up--the modulation on your signal is confusing the simple SWR circuitry--it takes more sophisticated circuits to tune up with an amplitude modulated signal.

Zack Lau W1VT
ARRL Senior Lab Engineer
May 17th 2012, 18:54

speedmaster

Joined: Apr 18th 2011, 12:20
Total Topics: 0
Total Posts: 0
Thanks, Zack. Tomorrow morning I'm going to drop the radio off with my elmer. He's going to keep it for a few days and try to figure out why I can't get it to low power for tuning.

Chris
May 17th 2012, 19:32

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

According to the manual (page 1-12), pushing the H/L key (14) should reduce the power to 1/10 for external autotuner tuning.

Zack Lau W1VT
ARRL Senior Lab Engineer

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