At Point #1 on the drawing (the output of the mixers) I expect to see 20 mhz and the 100 hertz beat note. My plans were to put a 3 db attenuator here and expecting it to provide a 20 mhz termination/match for the 20 mhz part of the signal. Do you think this would be an adequate way to terminate or does it need a better system ?
The Op Amps at Point #2 would be a something like LT1000s or so and they basically would only allow passing of the beat signal as they do not have the response to handle the 20 mhz signal. They would have to have a lot of gain and also would simple RC low pass filter say for 120 hertz be good enough ? The DBMs have 7 db conversion loss, the RF port goes into 1 db compression at +2 dbm. The LO ports can take +13 dbm absolute, and are recommended drive at +7 dbm. What voltage range can I expect out of the mixers (next question would be how much gain do the op amps need....).
At Point #3, I thought about using some type of Schmidt Trigger like a 74AC14. But is it necessary ? The 5370B can be set to trigger from zero to 2 volts or so.
If the 5370B can see one shot performance of 20 pS (2x10-11 at one second) then a 100 hertz beat note should give 2x10-13 at 1 second, 2x10-14 at 10 seconds, 2x10-15 at 100 seconds and so on.......correct ?
Brian - KD4FM
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