Corby -
>From the schematic it does not look like anything special but only a 50 ohm in and out circuit with fairly high isolation due to the common base of the second BFT66. You may be able to simply use a newer MMIC from one of the many sources to replace the assembly if you know the gain. Get one with more gain than needed and then use a resistive attenuator for additional isolation. I did not see the variable Johanson on the schematic and there are no tuned circuits that I can see, at least not LC wise. I would think you could measure the Johanson by removing it from the board. Since I do not know the exact purpose of the amp I do not really understand why it has to be so critical. Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 -----Original Message----- From: time-nuts <[email protected]> On Behalf Of [email protected] Sent: Sunday, October 14, 2018 11:55 AM To: [email protected] Subject: [time-nuts] RF isolation amplifier question 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 _______________________________________________ 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.
