[AMRadio] High-power tuners WHY?


Jim Candela jcandela at prodigy.net
Fri Dec 8 11:32:32 EST 2006


Hi all,

   I'm watching this exchange, and I keep asking myself the question, WHY? ;-)

Lets tie together multiple threads here, the RF amp, Loop antennas, and high power tuner. You could take that 450TL push pull rig, with variable link coupling, and match to 450 ohm open wire feeders to a loop antenna. No big-ass antenna tuner, and no 50 ohm resistive feed line.  The lack of a separate tuner will boost efficiency, and at the same time the FCC would have no place to insert their precision watt-meter. Now the only way to measure power is by ERP, and this is much less precise, and hard to model with typical antenna installations. That occasional peak to 1501 watts PEP will not be a factor anymore.

It always makes me laugh when I see that antenna tuners now cost more than what a good linear amplifier did just a few years ago. Why do we think it is necessary to have a 50 ohm unbalanced and 1:1 (50 ohm referenced) load imposed on the transmitter, especially one with a push pull swinging link final? Yes it is easier to provide harmonic suppression at 50 ohms, but there are other ways to do it with balanced feedline (resonant stubs).

My 2 cents!
Jim
JKO






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