[time-nuts] New topics (was Re: He is a Time-Nut Troublemaker....)

[Magnus Danielson]

John Ackermann N8UR skrev:
> 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?

It would, unless you are able to use a double-mixer approach of some 
sort such that it cancels out.

I was expecting something simpler and quieter, but the usual suspect for 
such solutions has been quitet. A number of different approaches could 
be used naturally. I guess one would prefer a solution where a control 
loop could be created.

Cheers,
Magnus