[R-390] Meters

[Tisha Hayes]

The line level meter is a straightforward device. Measuring AC voltage
through the resistor network attached to it. It is probably nice and linear
(with maybe the exception of frequency response).

The carrier meter is measuring DC and with that carrier pot and everything
else around it is probably not linear and has no reference to any particular
number (like S-Units, uV or dBm). As has been said by others it has mostly
been a tuning aid and not something that you could use to compare the merits
of one receiver against another or even what you may have done during an
alignment.

For alignments I use a Sinadder and a really good, accurate signal generator
with some decent attenuators.

I have been tempted to create a new scale for the carrier meter (and the
line meter while I am at it) that would really represent some "value" but
after hacking around in that carrier circuit I just found the results not
that easy to replicate (comparing the signal generator output in dBm against
the Sinadder and the meter movement, even across different 1 MHz bands).

Thinking about what the original R-39x designers had in mind, they were not
trying to create a piece of precision laboratory equipment. The carrier
meter movement is just relative. The line meter movement is a bit more
important if you are pumping audio into a phone circuit or a recording
device.

-- 
Ms. Tisha Hayes/ AA4HA
----------------
Factory certified interoceter repair center.
"Remember, use only genuine interoceter parts."
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