[time-nuts] Re: What phase variations to expect in a DMTD due to temperature fluctuations?

[Lux, Jim]

On 10/24/22 4:59 PM, Bob kb8tq wrote:
> Hi
>
> I think you will find that a lot of these GNSS gizmos have ceramic or SAW filters
> in them. That’s likely not true for a device that covers from above L1 down to below
> L5 in one gulp. It is the likely approach for an L1 or L1 / L2 sort of device. It’s almost
> certainly how a “telecom” antenna is done.
>
> Bob
>
Our receivers are L1/L2, but yes a discrete LC filter.  But SAW devices 
have a noticeable tempco too.  30 years ago I used to assume a 100ppm 
box for 100 degree change, with a parabolic curve, but I can't remember 
if that was Si or LiNbO3 .





>> On Oct 24, 2022, at 3:59 PM, Lux, Jim via time-nuts <time-nuts at lists.febo.com> wrote:
>>
>> On 10/24/22 12:49 PM, John Miles via time-nuts wrote:
>>> The 1 ps/C figure is typical of most components other than magnetics.  Some
>>> RF transformers clock in at 10 ps/C or more, and some don't seem to have
>>> much of a phase tempco at all.  And as Javier points out, the choice of
>>> cabling can have a big influence as well.
>>>
>>>   
>>
>> We didn't measure it separately for our L-band LNA/BPF system, but I'd be willing to bet that it's the filter that dominates the time delay tempco.  Changes in L and C with temperature are well known, and changes in tuning will change the delay.
>>
>> In our system we're looking for uncertainties << 1ns, over 0-40C temperature range, so 30 ps/K is a big number.
>>
>>
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>