Chris wrote:
Band 2 should work from -20dbm (22mV RMS) right across its 10 MHz to 1
GHz range according to the manual. Even with 190 MHz into it it takes
at least 30mV to start triggering, sometimes up to 40 mV. 40 mV will
reliably fire it across its full range once it warms up a bit.
Band 1 specs are 22 mV from 10Hz to 1 GHz, and that band triggers with
just 15 mV at 10 MHz, but needs 25 mV at 100 MHz.
Band 3 specs are 12 mV at 1 GHz to 1.2 GHz (needs 15 mV @ 1GHz)
Ahh, I had missed that you were feeding the 10 MHz from the divider
to the *measurement* inputs. It sounds like a triggering issue.
Is the trigger coupling switchable from DC to AC, and is it
adjustable for trigger level?
It is not unusual for the trigger point to drift a bit as a counter
warms up, but at any temperature you should be able to find settings
that will allow it to trigger on inputs at least close to the minimum
the manufacturer specifies. The figures you are seeing are not way
out of bounds, especially if the trigger coupling and level have not
been adjusted for optimum triggering.
Again, note that the divider output is unipolar (positive-only, does
not cross 0V). With a TTL input, you should get good, stable
triggering with the trigger coupling set to DC and the trigger level
set to ~+0.5V on the positive-going edge. With sine-wave inputs, you
may get best results with AC coupling and a trigger level at or near
0V. Look under "triggering" in the manual to see what the
manufacturer recommends.
It's just like the triggering on an oscilloscope, if that helps --
what you would do to get a stable scope display is also what you need
to do to get a stable frequency reading.
Best regards,
Charles
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