Bruce Griffiths wrote: > George > > In the JFET frequency doubler: > 1) Surely the 50 ohms should be is series with the the voltage source V3 > for the simulation? > Correct. I did a cut and paste "without rotate" there. > 2) Usually a 1:4 impedance ratio step up transformer on the input is > about right with a similar transformer used to step down the output > (perhaps an even higher impedance ratio transformer (8:1, 9:1?? may be > better). The maximum turns ratio depends somewhat on the maximum > allowable drain voltage swing which in turn is limited by the drain > supply voltage. > I will re-run with the this in mind and will repost. > In the voltage offset circuit: > > 1) The junction of R9 and R12 should be connected to the offset source > (+5V??). > This is what I didn't get about the original circuit. I was scratching my head as to the purpose of a variable R9 when the only value that made sense was when it was set to the "0" position.
> I dont understand what the 7812 does in this circuit. > It was there in the original circuit so I modeled accordingly. Actually I ran some simulations with PS voltage variation to see the effect as well. In that case I removed the 7812. > Isolation amplifier looks OK. > > Bruce > This is a very nice design and the AC analysis shows a bandpass around 10 MHz with 20 MHz BW. The only issue I see there is that it needs 50 parts of 6 different values. This might be difficult to implement on a small board and would be prone to error for people trying to assemble their own board. The way I see the final product is a bare board and possibly a kit. It has to be easy to assemble and minimize errors. Actually, I was looking at the isolation amplifier provided in the C.M. Felton Paper: http://www.darksmile.net/ee/Superimposing_Low-Phase-Noise_Low-Drift_Instrumentation_Techniques_On_RF_Design.pdf It is relatively simple and would use similar devices as the Frequency doubler. I will upload more info as I compile it. George _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.