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Continuous tuning amplifiers

Jan 2, 2021
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I was listening to a Old ham operator who has been a ham since 1970 talking about all of his amplifiers are continuous tuning no matter what band it will turn to it. For instance if they create another band he will be able to tune his amplifier without doing any modifications. I have never heard of a continuous tuning amplifier if anyone have any information I would like to hear from you.

KK4ZDR
 

Some amplifiers replace the band switch tap with a roller inductor. Rather than having a coil with a tap for each band, you get a coil that rolls when a front panel knob is turned. As it turns, a contact rolls across the coil and provides a continuously variable amount of inductance. It sounds like a nice feature. However, dirt, dust and age have killed many roller inductors and made repairing some amplifiers using them, very difficult. Don't even touch that knob while the amp is keyed and under load. The slightest movement will easily cause a permanent arc wound on the coil, right in the place you need it to tune most often.
 
The disadvantages of the roller inductor can be nearly eliminated with just normal use and maintenance (cleaning). If it sits without any use for years, don't just expect to fire it up without cleaning the coil and roller surfaces. You may get away without doing it but, one dirty spot on the coil can wreck it, if the roller lands in that place.

This is one part that if you have the choice, you'll want to go overkill on. Especially if you use 10 meters or AM. The high RF currents and sustained carrier can easily cause a roller inductor that is too small, to heat and burn up. When properly sized and maintained, they are dependable enough that most of the largest HF military transmitters (Rockwell Collins) used them at the 10kw level.

Those exact roller inductors rated for 10kw, actually turned up in some military surplus places back in the 1980's and 90's. I got one from Fair Radio sales. Square pancake as I recall. Wonder if that's the beast Captain is working with...
 
Some amplifiers replace the band switch tap with a roller inductor. Rather than having a coil with a tap for each band, you get a coil that rolls when a front panel knob is turned. As it turns, a contact rolls across the coil and provides a continuously variable amount of inductance. It sounds like a nice feature. However, dirt, dust and age have killed many roller inductors and made repairing some amplifiers using them, very difficult. Don't even touch that knob while the amp is keyed and under load. The slightest movement will easily cause a permanent arc wound on the coil, right in the place you need it to tune most often.
 
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