Sunday, May 8, 2011

SMite via SimSmith

A pQRP friend and fellow builder, Ilkka - KF7LDX, has been Homebrewing a Knightlite SMiTe Build, see his writeup at:

The original circuit and documentation can be found at:

As seen by my previous posts, I have been playing with the SimSmith program. Ilkka's build provided an opportunity for me to model another output tanks circuit. I have been collecting data, and modeling the circuits that I find. I layout the components, insert their values, estimate the driver impedance, and let the SimSmith Program do the work.

The Circuit and Impedance Match

As per SimSmith, it appears that the published SMiTe circuit provides one of the best matches that I have found, assuming the PA 2N2222 drive impedance of about 100 ohms.

The computed SWR and Second Harmonic Suppression

As can been seen, the output circuit provides a good match at the Oscillator Frequency (solid line) and good suppression at the Second Harmonic (dotted line).

I would not mind building this circuit.

LOAD R:50.0 X:0.0 load:
SHUNT_CAP Fd:820p Q:1.0K @MHz:0.0
SERIES_PARALLEL_TRAP Fd:220p Hn:2.2u Q:1.0K @MHz:0.0
SHUNT_CAP Fd:820p Q:1.0K @MHz:0.0
SERIES_CAP Fd:.01u Q:1.0K @MHz:0.0
SHUNT_IND Hn:22u Q:1.0K @MHz:0.0
GENERATOR MHz:3.6864 R:100 X:0.0
CONTROLLER lower__Scan__Freq:1.0 upper__Scan__Freq:9.0 #__of__Segments:500.0 SWR__R:100 SWR__X:0.0 SWR:1.2


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