Well said Sent from my iPhone
> On Oct 14, 2018, at 4:14 PM, Gerhard Hoffmann <[email protected]> wrote: > > > >> Am 14.10.2018 um 18:47 schrieb Dana Whitlow: >> Corby, >> >> Now that I learn that the BFT66 is a "wild one", I'd remark that stability >> is >> indeed the likely issue. I was puzzled by the presence of that capacitor in >> the first place, as this circuit is clearly neither tuned nor of especially >> high frequency capability. > If the circuit really has a stability problem, one could try first to > harvest the low-hanging fruit and change the base resistors from > 2R5 to 22R, maybe even more. > > That won't damage the noise behavior, that has already been done by > the 180R in the input. The only possible reason I see for the 12 pF is > to kill the gain of the first stage at VHF+. It may be a disservice to > the 2nd stage, depending on the isolation performance of the R > between the upper emitter and the lower Collector. > > Also, the 100nF+10nF caps in the base divider will parallel resonate > at +/-10 MHz, depending on layout; and that means "no real decoupling" there. > > All in all, the circuit is somewhat weird; the BFT66 was a boutique part > even in it's heyday: low noise, high gain, high ft, high price and a package > that was not really RF-ish. The second stage is abt. as low cost as you could > get. > With all-3904/3906 that would be a text book AF amplifier. > > Have a nice Sunday evening, > > Gerhard, DK4XP > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
