Chris wrote:
I have the 10MHz output from David's divider feeding the counter. When fed from this the Band 2 seems unreliable starting at 10MHz. If I feed it 10Mhz at 50mV from my sig gen it starts reliably. Is it a mismatch from the divider, or has it perhaps not got enough drive level?
First, what does the counter manufacturer's specification say with respect to acceptable signals at the external reference input?
Second, what happens if you feed the TB output directly to the counter's reference input?
IIRC, the outputs of the Partridge divider are 5V TTL from a ~50 ohm source, so low peak-to-peak signal amplitude should not be an issue. If anything, the divider could be overdriving the counter's reference input. Note that the TTL signal ranges from 0V to ~+5V and does not cross ground -- if the counter is expecting the reference to be bipolar (i.e., if it switches on a zero-cross), it may not respond reliably to TTL levels.
Beyond that, depending on how the counter terminates the external reference line, you may have steps or ringing at the reference input (see the thread on terminations). Look at the counter's reference input with a high-impedance (divide by 10) scope probe to see what the feed looks like there.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
