Frequency = 236 to 241 MHz ( Vgs = -0.1 to -1.7 V) when AC-coupled into 1 MOhm oscilloscope.
          = tunable 236 to 244 MHz ( -0.1 to -1.7 V) into a 50 Ohm spectrum analyzer.
            Sensitive to nearby motion.  Very sensitive to wiggling the tank capacitors.
            -40 dB sidebands at +-50 kHz.
            -3 dB bandwidth is 10-15 kHz
            jitter about 10-20 kHz
            absolute power = -7 dBm

2n5459 - n-channel JFET
Colpitts Oscillator

Rd = 5100 Ohm

Rg = 1 MOhm

Vdd = 17.4 V
C = 5 pF
Vgs = -2.13 V

Cf = 5 pF
C1 = C2 = 2 pF
L = 2 finger loops

Ls = 3 finger loops

Built on proto-board, closely packed.
An improved design would be to add a buffer amplifier, such as a follower (common drain).


                                +Vdd
                                |
                                +------+
                                |      |
                                Rd     C
                                |      |
     +--------Cf----------------+      Gnd
     |                          |
     |                          |
     |    Scope                 |
     |   |      |               |
     |   |      |               |
     |   +--Ls--+           |---|
     +--+---L---+-----+---->|
        |       |     |     |---|
        |       |     |         |
        C1      C2    Rg        |
        |       |     |         |
        |       |     |         |
        +--Gnd--+    Vgs       Gnd


W. M. Hetherington