Sometimes a 10 Ohm resistor from Base to RF ground will rescue you. 73 de N1UL
Sent from my iPhone > On Oct 14, 2018, at 4:31 PM, Bob kb8tq <[email protected]> wrote: > > Hi > > What you have there is known as a cascade buffer amplifier. The common base > stage combined with the common emitter has some well known issues at high > frequencies ( like UHF / microwave). That’s the tradeoff for having really > good > isolation at HF and usually at VHF. > > Put a sniffer loop near the circuit and look with a good wide range spectrum > analyzer. > Drive the circuit over a range of input levels. Try terminating the output > with odd loads. > Watch for birdies popping up and then fiddle things to kill them. > > As others have noted, those may not be the best parts to use for this. I > would not replace > it with something simple, it should have a lot of isolation when it works > correctly. > > Bob > >> On Oct 14, 2018, at 11:54 AM, <[email protected]> <[email protected]> wrote: >> >> Hi, >> >> I removed this amp from the EFOS2 Maser as it was intermittent. >> >> Of course now I can't get it to fail on the bench! >> >> I have fabricated a new PC board to replace it and have the components on >> hand. >> >> Note the 12pfd cap on the collector . >> >> Some notes I have indicate is select at test and that is it a glass >> capacitor. >> >> The as built unit has a johansen 50pf that looks to be an early version >> of surface mount with leads soldered on. >> >> How do I determine what value to install on the new amplifier? >> >> Cheers, >> >> Corby<efosiso.jpg>_______________________________________________ >> 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. _______________________________________________ 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.
