On 7/18/2020 6:25 PM, Magnus Danielson wrote:
Hi, A similar approach is used in the 10811 replacement oscillator setup for the 5065, where a 7474 is used to divide 10 MHz to 5 MHz. Signal conditioning consists of a DC-blocking cap and a pair of resistors to bias the mid-point. The produced noise is at least 10 dB worse than you would expect. This impacts long term stability response as I have reported earlier. At least using the square-up design in TADD-2 would help, even thought that one won't work for 100 MHz, so it needs a bit of tuning. There are chips that solve this. Cheers, Magnus
Yes, the simple pair of resistors doesn't work well on TTL. That was probably done by a production engineer, who was working above his pay grade. We can't all be Len Cutler. OTOH, that circuit works well with 74ACXX circuits. We did that at 80 MHz in the 5071A and it worked well. Back in the 70's when I worked for Zeta Labs, my boss taught me to use a 1 transistor buffer that had a pull up resistor on the collector and a resistor from the collector to the base and a resistor from the base to ground. We used it in all our designs and it worked well, despite being ridiculously simple. My boss was really smart. That is what they should have used in the 5065. Rick N6RK _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
