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Author Topic: Yaesu FL 2100B Bias  (Read 3344 times)
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« on: February 07, 2014, 03:14:49 PM »

I just replaced 2-572B's in my FL2100B linear, I had modified the bias supply a few years back to cutoff the 2 russian tubes I had in there.The bias supply in standby now cuts off the 572B's. In the operate mode (no carrier) the ideling current is 40ma, the book calls for 90ma of ideling current. The class of service is class (B) it is a grounded grid linear. With the 40ma is it still class (B)?

John W9BFO   
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« Reply #1 on: February 07, 2014, 04:38:33 PM »

Back about 10 years ago I was using an old NCL-2000 on the whats for dinner net.

I had noticed the amplifier worked OK on AM with much less than the idling current recommended for ssb. OK meaning it was not producing a nasty signal on frequency off to the sides on a quiet afternoon on the band.

Bill W3DUQ confirmed this as a known way to improve efficiency using linear AMplifiers on AM.

The practice probably goes way back to before plate modulation's almost universal acceptance in broadcasting when linear finals were used.

Some amplifier ##experts## have recently discovered this practice and have reported it to the masses.

In your case I would try it and see. It probably will not be so great on ssb but who uses that anymore anyway.
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