No, the mode shouldn't matter. If it does, then the tuner is sub-par.
I don't recall ever seeing a fan in a broadcast ATU. Why should
hams accept one? A fan is in a ham tuner for two reasons:
1. The inductor is cheap or not up to the demand expected of it.
2. A fan is cheaper to use than a good inductor.
I guess there's a third reason: A fan allows the mfr to claim a
higher power handling spec.
The problem can be solved but probably not by purchasing any of the
low cost tuners on the market for hams. One option is to purchase an
older tuner like a BC-939 and make a few minor rewiring mods that
allow for it to be returned to its original status if necessary.
Another one is to get a decent inductor like one taken from a
broadcast phasor (they show up at hamfests and on eBay). The inductor
doesn't have to be continually variable. It is possible to get copper
tubing and wind a good inductor and tap it, or purchase a big edge
wound Johnson inductor and tap that with clips (not alligator clips)
or solder short copper wire pieces on it at the right points and
connect them to banana jacks. Then use a moveable tap with a banana
plug on the end. No matter how it is done, use a coil that is massive
enough that it doesn't dissipate much heat. at a minimum, 1/8 inch
o.d. tubing is good. Use PVC sewer pipe, the stuff that's 4 or 5
inches o.d. for a coil form. Wrap about 10 feet on it (you have to
rig it up as a jig and have a friend turn it while you hold the
tubing) for practice to get a feel for handling it so it doesn't
buckle. Even the KW Matchbox has a halfway decent tapped coil.
Also, hams need to forget the idea that one tuner can or should do
everything well. That's like thinking there is one good antenna for
1.8 to 30 MHz. It's just not true.
73
Rob
K5UJ
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