OKAs an experiment, just for the curious, set your signal generator frequency
to what the R-390 is set to and connect the signal generator, which is set for
about 10 uV, to the unbalanced RF input BNC. Set the R-390 for normal
operation with the function switch set to MGC, adjust the antenna trim and
R-390 KC dial for a peak carrier level meter reading. Now adjust the RF gain
control for near full scale on the carrier level meter. Record the carrier
level meter reading and the diode load voltage.
Now disconnect the coax from the Signal Generator and insert a BNC "T"
connector and again reconnect the signal generator to the R-390, connect a 50
ohm resistor to remaining arm of the BNC "T".
What does the carrier level meter now read and what is the diode load voltage?
Increase the signal generator level until the carrier meter and diode load are
back to the previous readings. How much additional signal is needed from the
signal generator to bring the meter reading back to the original readings?
Also curious,Jim
Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy
On Tuesday, October 8, 2024 at 10:43:30 AM CDT, Bob Camp <kb...@n1k.org>
wrote:
Hi
If you terminate the generator in 50 ohms, that is the expected way to use the
generator. When the dial says “1uV” you get 1uV.
If you have the generator unterminated, that is *not* the expected way to use
it. You set the dial to “1uV” and you get 2uV. You are not using it in the
intended fashion (at least not calibration wise).
Simply put: That 6 db does not count if you are looking for 1uV.
If you look a 50 ohm termination and say it’s a 6 db drop, that’s not a drop
that counts in this case.
Bob
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