John Miles wrote:
The spec for the 10811A's trimmer range is +/- 10 Hz, actually. Seems
doable.
There was a good thread on the list back in late 2006 where some of the
pitfalls of the DMTD technique in general were discussed. It seems that
achieving optimal performance is a lot less trivial than anyone would like.
If someone wanted to build a "minimum effort" system with a lower short-term
floor than the 5370, my understanding is that it would require:
- a 10811-class OXCO tuned to generate beat notes of several Hz
- a mixer of some sort with good IF response down to DC
You need some form of mixer IF termination and amplification/buffer,
which Bruce also have done work on.
- four good isolation amps (which thanks to Bruce's recent work is not a
difficult or expensive issue)
- some sort of delay compensation on one of the inputs may be needed to
avoid decorrelation of the transfer oscillator's effect between the two
channels
As I have explained in a recent thread, this is not necessary if one
takes the sampled data processing route rather than the ZCD path to
measurement and data correlation. The phase offset between the ZCD
triggers causes transfer oscillator decorrelation losses. A synchronous
sample-for-sample processing of the two channel pairs maintains a very
low time difference and the loss is negligable as it only exposes very
high frequency noise as sample error exposes.
- a sound card with good differential-phase stability
You also need processing software. While it does not have to be hard,
there is a number of processing pitfalls to fall into that could make it
a bit difficult to get accurate results.
Cheers,
Magnus
_______________________________________________
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.
