On Fri, Jan 30, 2015 at 07:35:34PM +0100, Gerhard Hoffmann wrote: > As usual, it depends. If you want absolutely deep notches, it is > easy with the usual molded chokes > to produce craters at 5 and 15 MHz that meet at 10 MHz, even > producing some loss there.
Hello. Let me sum up everything and please correct me: the square-law characteristic of devices should be avoided, so the configuration of the doubler must be some sort of "ideal" full wave rectifier it's better to use diode-connected transistors like the 2N2222 because they are less noisy than Schottky diodes at frequency < 40MHz (what about the normal P-N diodes?) matching is very important, so monolithic doubles or quadruples could be the right choice, provided their other characteristics are compatible and the substrate connection is not a problem bandpass filtering must be avoided because of added unwanted temperature-dependent phase shifts, so harmonic suppression should be obtained by notch filtering the notch filters could be made using quartz resonators but their high impedance versus LC ones should be taken into account and, anyway, it's difficult to find exactly tuned quartz (particularly for the higher harmonics because of the overtone cut) - the sharpness of quartz filtering is not needed anyway because the harmonics are distant enough for LC filters (what about ceramic resonators?) I add some questions. I saw that most of the doublers out there are using a center tapped transformer to obtain +-180 while the Racal circuit use a single ended input / balanced output transistor discrete differential amplifier, thus combining phase splitting with gain and impedance matching (but not isolation). That configuration should be avoided because the transformer is normally a better matched splitter? On the base of many considerations, the Racal circuit is flawed in many parts; it's anyway good enough for the counters it was designed for or the better performance of other doublers will show up? Best regards, Andrea Baldoni _______________________________________________ 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.