Re: RD16HHF1 in the uBITX #ubitx

K9HZ <bill@...>
 

That 40% drop explains a lot.  I would still like to see that confirmed by test.  It could also be compensated for on board to keep the drive level flat. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

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On Feb 15, 2018, at 11:41 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

As reported here:  https://groups.io/g/BITX20/message/40938
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.  They need to be driven harder for good results at 30mhz.

Jerry, KE7ER

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