[G0HZU_JMR]

In this case I think the loop gain will collapse if the JFET Idss gets to 6mA or so. I think the MPF102 is a classic process 50 JFET but the datasheet implies a huge range in Idss is possible from 2mA to 20mA. So the builder of this circuit could be disappointed if the Idss of their batch of MPF102 JFETs was fairly high.

The 2N5484,5,6 series are also process 50 (from memory) and these JFETs are graded across this Idss range so a 2N5484 should have an Idss within 1 to 5mA according to the datasheet.

I think it would be fairly fatal to select the 2N5486 with its Idss range of 8-20mA as the Vds of the JFETs would collapse to little over 1V (because of the 1k ohm resistor in the drain) and I think the loop gain would collapse way below unity. So I think the oscillator wouldn't start up. The 2N5485 would be marginal but it might work OK. The 2N5484 would be the lowest risk assuming the Idss was somewhere around 2-4mA.