[time-nuts] DMTD Ideas
kilodelta4foxmike at gmail.com
Fri Oct 2 01:17:31 UTC 2009
I have toyed with the idea of building a Dual Mixer Time Difference
setup for testing oscillators. I have attached a drawing I made and I
have a few areas I need to clear up.
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
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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