: I don't see any fundamental problem with file:Hartley osc.svg. It may forward bias the gate, but that should just impact amplitude and stability. Choosing the product of drain current and load resistance less than 0.5 V would keep things in reasonable shape. 
 : The op amp implementation file:Oscillator hartley opamp.svg has the inputs backwards (see above), the low-Z output should drive the tap, and the design should not use an infinite gain op amp. Think of it this way: the op amp output is putting a zero ohm load resistor across the tank and killing all Q. The figure should be nuked. 
 : I don't see any problems with file:Oscillator comparison.svg; they should work. One resistor biasing is not the best, but the high Z collector drives top of tank and lower Z input is taken from tap. Colpitts version has extraneous isolation cap. 
 : The .png is the same as the third .svg but uses more robust three resistor biasing with Ce bypass. If you can make the .png work, then you can make the third .svg work. 
 : I'm not so sure that practical circuits should be shown. WP is an encyclopedia and not tutorial about circuit design. There are many subtle details to real circuits. 
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