[R-390] R-390A Use of CX-2919 and CX-1363 adapters

[Larry H]

I was checking the stage gain of a couple stages in the IF deck I am
working on and noticed that the TM-856A specifies to use the CX-1363
adapter, but the TM-11-5820-358-35 specifies to use the CX-2919 adapter and
that it comes with the AN/URM-25D.  Well, the book I have for the 25D
specifies that the CX-1363 adapter comes with it and not the CX-2919
adapter.  However, the book for the 25F specifies that the CX-2919 adapter
comes with it.  I know this seems trivial, but since I don't have a CX-2919
adapter and wasn't sure what it was and it isn't listed in my 25D book, I
had to go look it up.  Turns out that the CX-2919 adapter is simply a .047
mfd cap in series with the signal to block DC from damaging the URM-25's.
And, the CX-1363 adapter is a .1 mfd cap in series with the signal for the
same reason.  It looks to me that either adapter would work fine for this
purpose.  I searched through our online doc about this, but couldn't find
it.

I'm just curious - do many of you URM-25 users have a CX-2919 adapter?

It also looks to me like a 50 ohm load should be used in front of these
adapters in order to have the URM-25's meter read as accurately as possible
(they need a 50 ohm load).  This is because the books are specifying a
particular level of signal and these adapters provide no loading at all.
But where a specific signal level is not specified or need to be known, the
loading is not necessary.

Regards, Larry