Esa Heikkinen wrote: > > Its probably better to increase the emitter current to 40mA or > > so and place 47 ohms between the emitter and the output coupling > > capacitor a and accept the resultant +7dBm output. > > The transistor dissipation will increase and it may be better to > > substitute something like a 2N5943, 2N3866, 2N 5109, BFW16A > > or similar. > > I don't have those 2N types but after some digging found 2N2219A. > Changed that and 47 ohms from emitter to the ground. I run it first with > 6 volts, then with 9 volts and then with 12 volts but have to stop with > uncomplete sweep because it become very hot. > > Increasing the current does help with amplifier linearity but not so > much. However the spectrum looks little bit better now but it's still > out of spec: > > http://www.amigazone.fi/files/gpsdo/544-7.png > http://www.amigazone.fi/files/gpsdo/544-8.png > http://www.amigazone.fi/files/gpsdo/544-9.png > > >> About the only way to achieve the distortion you observe is if the >> capacitance of the wire connecting your emitter follower to the 10544A >> output is too large (around 50pF or more). >> > > It's about 30 cm. long microwave coax taken out from some RF stuff > (maybe old cellphone). It's measured capacitance (at the other end free) > is 36,2 pF. > > I'll send the picture later if still needed.. > > Esa
A quick and dirty fix is to use a low Q (use a resistor in series) inductor connected between the cable output and ground (or equivalent location) of the right value to cancel most of the input capacitance at 10MHz. Bruce _______________________________________________ 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.
