Peter Chadwick:
>... ... ...
>>I would be very inclined to measure the IMD with W8JI's 3 tone test,
>>with 2 of the tones about 40 or 50 Hz apart - that will show up any
>>problems with the time constants in the SG circuit as well as in the HV
>>PSU.
Rich Measures:
>The G2DAF circuit's screen voltage remains constant during such tests.
>However, with voice modulation, the screen voltage - and the IMD -
>fluctuate wildly.
* This is not true. The screen voltage will most certainly fluctuate, as thats
* the general idea with the circuit. However, that does not mean that IMD
also * "fluctuates wildly"!
>One of the more curious things I ran into with measuing the distortion of
>DAF amplifiers on the air, is that DAF owners would reduce the grid drive
>to prove that the DAF circuit was clean, and subsequently turn the wick
>up after the test to increase power output.
>Rich...
* This will apply to any amp.
>There is not much new under the Sun concerning grid driven tetrode SSB
>amplifiers. The grid current region is not the linear region, use plenty
>of anode volts, place the termination close to the grid, neutralization
>might be nice above 10MHz, and regulate the screen. These requirements
>are fairly easy to meet.
>cheers, Lars
>Rich...
* You can´t take facts wich applies to amplifiers running under FIXED class
* of operation, and directly translate those facts to amplifiers wich like
* G2DAF runs under FLOATING class of operation.
* It´s interesting to note that in the world of audio amps, the most exclusive
* designs use FLOATING class of operation...
* 73´s de Lars /SM3BDZ
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