[time-nuts] New topics (was Re: He is a Time-Nut Troublemaker....)
John Ackermann N8UR
jra at febo.com
Tue Dec 23 20:28:47 UTC 2008
Hal Murray said the following on 12/23/2008 01:58 PM:
>> 2. Several measurement techniques require a given phase relationship
>> (e.g., quadrature) between DUT and reference. For HF frequencies (ie,
>> 5 or 10 MHz) is there a *practical* phase shifter design covering
>> 180+ degrees that doesn't involve switching various lengths of coax
>> in and out of the line?
>
> PLL up by a factor of N, use that to drive a DDS, then filter. Maybe a pair
> of DDSes will get better tracking.
>
> For each possible phase offset, you need N slots in the table. (N/4 with
> more work)
If doing phase noise or short term stability measurements, wouldn't the
noise of the DDS impact the results?
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