[R-390] 1970 Navy R-390A Tech Ref c/l meter readings

[Larry H]

I found one place in this tech ref (NAVSHIPS 0967-063-2010) that gives a
clue to the relation of microvolts fed into the balanced antenna connection
and the c/l meter reading, and that's on page 5-21 at item 17 in the TABLE
5-5, TROUBLE ISOLATION.  Briefly, it says that a 10 uv input should read 40
db on the c/l meter and a 100 uv input should read 60 db on the c/l meter.

Unfortunately, that is not true, 10 uv should read 20 db and 100 uv should
read 40 db.  The relation of 'uv in' to 'c/l meter reading' is quite
simple: as the uv input level is multiplied by 10, the c/l meter db reading
is increased by 20 db.  So, 1 uv = 0 db, 10 uv = 20 db, 100 uv = 40 db,
1,000 uv = 60 db, 10,000 uv = 80 db, and 100,000 uv = 100 db.  A nice clear
graph of this relation can be seen in the tm-11-856a r-390a tech ref on
page 75.  Here's a link to this tech ref on our website: TM-11-856A.pdf
(r-390a.net) <https://www.r-390a.net/TM-11-856A.pdf>.

In my experience, the c/l meter normally works as described in the
tm-11-856a r-390a tech ref when the AGC and c/l meter circuits are working
as designed.

Regards, Larry