MFJ-974 Balanced Tuner

[WA5KRP]

Try calling MFJ's technical support: 1-800-647-8324

Good luck!



WA5KRP
Texas

[AL7N]

How/where are you measuring the "SWR"? Internal meter in the antenna tuner, meter at the rig, or what?

Maybe it is a measurement problem instead of an actual matching problem.

Another possibility is a faulty connection in the coax
between the rig and the tuner.

Also, is this one of the tuners that has the toroidal
balun at the output of the tuner? Sometimes you have
to add a jumper between the "wire" antenna tuner
output post and one side of the "balanced" output
connections to connect the balun into the feedline circuit.
Is the jumper there? I have some MFJ tuners that
require this kind of jumper to work. Otherwise the
antenna feeders are not even connected to the tuner output circuit!

Something like this is one of those deals where it is
so simple it has "gotta work". If it don't, the solution
usually turns out to be something basic and simple tht was overlooked somewhere.

Good luck!

AL7N

[K7KBN]

Sometimes, MFJ has a quality control problem, particularly with soldered joints. After first talking with tech support, I'd do a little snooping inside and see if anything is obviously loose or otherwise defective.

Can you receive signals on the various bands? Can you make the signals change in loudness (or make the background noise change in loudness) as you adjust the L and C combinations? If you can, that would seem to indicate that at least SOMEthing is working right...

[AL7N]

I am not familiar with the MFJ 974 unit. I do know that the MFJ tuners I have as well as an older B&W unit that has the same circuitry have a toroid balun that connects the balanced feeders to the unit, but in order to feed RF from the tuner circuit proper, you have to run a jumper from the "wire" (end-fed random wire) output binding post to
one of the "balanced" antenna feeder output connections. There is a dotted line painted on the rear panel showing this connection. The MFJ 974 might be different. But with the other MFJ units, the balanced feedline won't be connected to anything in the tuner without this jumper in place. The extremely high SWR indications you report look like the balanced feedline to your dipole antenna is not connected at all, so this is the first place I would look.

Investigate the circuitry in there where the "balanced" output gets it's RF from inside the tuner.

Hope you have success...good idea to call MFJ too and ask them about it.

Ed AL7N