[time-nuts] GPSDO Design

[Bruce Griffiths]

Oops wrong thread.

Bruce
Bruce Griffiths wrote:
> Eventually the flicker noise of most amplifiers (apart from chopper 
> stabilised and related amplifiers) will exceed the noise of a resistor.
> The internal zener noise will in most cases be much larger than 
> amplifier noise.
>
> The output noise (due to the filter components) of an RC low pass 
> filter is SQRT(kT/C) where C is the filter capacitance.
> For C ~ 1uF the noise is ~3.7 nV rms.
> Such noise will add about 3.7E-17 additional FM noise to an HP10811A 
> if applied directly to the EFC input.
> This additional noise several orders of magnitude less than the effect 
> of other noise sources, so the filter noise is unlikely to be a 
> significant issue.
> However the noise due to the resistor used to add a zero to the filter 
> response is not filtered by the loop filter capacitor.
> Only the low pass filter at the amplifier output and that within the 
> EFC circuit affects this.
>
> Bob Camp wrote:
>> Hi
>>
>> Back when the Z3801 was new, some GPS's would let you pick a specific 
>> geoid
>> model to use for altitude. Apparently it's a receiver side choice of 
>> what
>> model to use.
>>
>> Bob
>>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of John Green
>> Sent: Thursday, January 14, 2010 4:36 PM
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] Tbolt altitude error
>>
>> I had a Tbolt and a Z3801 both fed from the same antenna and they 
>> indicated
>> 26 meters differenence in altitude. The 3801 seemed closer to right. If
>> geoid error were the cause, it seems that both would indicate about the
>> same.
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>>
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>
>
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