[time-nuts] Broadband synthesizer

Jim Lux jimlux at earthlink.net
Wed Jul 13 12:55:11 UTC 2011


> On 7/12/2011 at 9:04 PM Bill Dailey wrote:
>
>> Ok, I have a dds receiver locked to a gpsdo, the radio can only be tuned
> in  1 hz increments but should be dead on. I can feed the passband into
> speclab via VAC and measure a carrier OTA.  No problem there...can get
> decent resolution but there is some uncertainty with regard to the dds
> (frequent dependent).  What I would like do is inject a known frequency to
> either zero-beat the carrier (assuming I can get something with millihertz
> resolution) or provide a non-superimposed carrier that I can reference via
> difference in speclab.  The whole point is to eliminate or measure the dds
> offset at a particular frequency.

>

Is this a one time measurement (i.e. you've got a DDS, and you're not 
sure it's being programmed correctly, and want to verify that it works)

Why not something like an accurately known XO with a comb generator (aka 
a "marker generator")  You've got a GPSDO, so presumably you have a 10 
MHz that's good to milliHertz (1 part in 1E10). Generate a comb at 
10,20,30,40,50.. MHz all the way up



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