Re: [time-nuts] Adafruit Ultimate GPS timing message arrival times

[Chris Albertson]

On Mon, Aug 1, 2016 at 9:48 AM, Bob Camp  wrote:

>
> The serial string is fine for an "eyeball clock". It’s not so fine for a
> GPSDO.
>
>
That is a good way to say it.  NMEA was designed for marine navigation.
Driving ships and boats across an ocean.So the NMEA that my water speed
sensor produced was good enough it is output at 1Hz. The NMEA is that
the "data needs to be valid within a second of when it is written".
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Re: [time-nuts] Effect of EFC noise on phase noise

[Gerhard Hoffmann]

Am 02.08.2016 um 22:24 schrieb Bruce Griffiths:


Uually a zero is needed in the bias stabilisation loop to eliminate 
low frequency gain peaking.


2 Meg across the 3.3uF remove the peaking. Nevertheless the circuit 
still has
problems with its time constants. Weird things happen if you let the 
transient analysis

run for a minute simulated time  (must increase n cycles for the source).
Probably I'll accept a higher low frequency corner for now to get reasonable
simulation times.

Remember, that is not a publication but a snapshot of work in progress.
Some part values may be just the result of "what happens if..." experiments.
Or that I have a large bag of 3.3u foil capacitors and would like to use
them up first, if possible.  :-)

regards, Gerhard
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[time-nuts] FDA1050 distrubution amplifier

[Ole Stender Nielsen]

All,

I have a Time & Frequency Solutions (Brandywine) FDA1050 distribution 
amplifier, the version with just one input.
The board inside has actually a connector for a second input, and I 
would like to see if this input could be put into use.
However, with no manual/schematics at hand (plus a number of jumpers on 
the board) I would have to do some reverse engineering.
As entertaining as this may be, I would prefer to dig into a manual, 
preferably one with schematics, if available at all.
Would any of you have documentation on the FDA1050 that could get me 
started?


Best regards
Ole
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Re: [time-nuts] Effect of EFC noise on phase noise

[Bruce Griffiths]

On Tuesday, August 02, 2016 01:03:58 PM Gerhard 
Hoffmann wrote:
> Am 02.08.2016 um 09:14 schrieb Bruce Griffiths:
> 
> 
> ... and a screen dump for the LTspice challenged
> 
> ;-) Gerhard
Uually a zero is needed in the bias stabilisation loop to 
eliminate low frequency gain peaking.

Bruce
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Re: [time-nuts] Another arrival time histogram: SiRF III

[Magnus Danielson]

Hal,

On 08/01/2016 05:49 AM, Hal Murray wrote:


It was setup to only send GPRMC sentences.
  http://users.megapathdsl.net/~hmurray/time-nuts/RMC-hist.png

Here is what it looks like over time:
  http://users.megapathdsl.net/~hmurray/time-nuts/RMC-offset.png

There are interesting glitches at 3 hours and 23 hours.  Anybody have any
ideas about what would cause that?


This most likely is related to scheduling inside the RTOS of the GPS 
receiver. Due to the frequency difference between GPS second and 
internal clock processing that we can expect, the scheduling needs 
re-alignment. There is an overlap between "late" and "early" which 
indicate that a dynamic scheduling, so depending on when things get 
ready it gets early or late. Variations within each time-slot is then 
due to processing variations.


Cheers,
Magnus
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Re: [time-nuts] Effect of EFC noise on phase noise

[Gerhard Hoffmann]

Am 02.08.2016 um 09:14 schrieb Bruce Griffiths:


... and a screen dump for the LTspice challenged

;-) Gerhard
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Re: [time-nuts] Effect of EFC noise on phase noise

[Charles Steinmetz]

Gerhard wrote:


The preamp will be classical.  Some JFETs in parallel  *  *  *
Cascode with a Zetex bipolar (or whatever they are called now).
 *  *  *
Without the cascode, the 1 MHz is not possible. It does not help that
the feedback limits the voltage excursions on the drain.


As you recognize, these FETs need significant drain-source voltage to 
give their promised performance (8v at the absolute minimum, IMO, and 
they really should have 10v).  You might try a folded cascode topology 
(sometimes called a "reverse cascode") to increase the D-S voltage.  It 
is a little more complicated, but should not have any material impact on 
the noise figure if it is done properly.


Best regards,

Charles


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Re: [time-nuts] Effect of EFC noise on phase noise

[Bruce Griffiths]

Gerhard, please send me the LTspice files,  so I can compare it with  some of 
my circuits.
The Groner preamp uses feedback to adjust the dc input at the input 
(paralleled) FET gate(s) to adjust the dc output to zero.  It uses a small 
value input coupling capactor with a high value resistor to bias the JFET 
(parallled BF862's). I had simulated a similar preamp architecture some years 
before the Groner article.
I suggested a similar preamp architecture on EEVBlog  but the responses 
indicated that most of the respondents appear incapable of rational analysis 
and just regurgitate the conventional approach.

Bruce
 

On Tuesday, 2 August 2016 6:19 PM, Alex Pummer  wrote:
 

 Ja Gerhard, bitte schicke mir den LTSpice file,

Danke im Voraus und
73
KJ6UHN
Alex

On 8/1/2016 6:34 PM, Gerhard Hoffmann wrote:
> Am 02.08.2016 um 02:42 schrieb Bruce Griffiths:
>> /"I'm working on a new amplifier based on IF3602 or BF862 FETs that can
>> use 10u foil only."/
>> /
>> /
>> Similar to that published by Groner in Linear Audio?
>> /
>> /
> I know that Groner exists from some web site, but had no personal 
> contact.
> Also I don't read Linear Audio other than 2 articles from Scott Wurcer 
> that I've bought.
> I highly regard Scott, he's the father of the AD797 after all and AD 
> fellow.
> I also had some conversations with him on that.
>
> The preamp will be classical.  Some JFETs in parallel, no source 
> resistors except
> half an Ohm for feedback, more would add to the input noise voltage.
> Cascode with a Zetex bipolar (or whatever they are called now).
> OP37 for loop gain. feedback from OP37 output for 50 or 60 dB gain.
> Post amplifier to 80 db or so.
> Without the cascode, the 1 MHz is not possible. It does not help that
> the feedback limits the voltage excursions on the drain.
>
> I'm not yet sure about the effective input capacitance. I get abt. 1 
> or 1.5 MHz
> bandwidth from a low impedance source. A few nF on the input capacitance
> would be ok, in the end I want it after a ring mixer for phase noise 
> measurements
> but I get unreasonably more in simulation, depending on if I measure 
> it from
> upper frequency corner with a larger input resistor or the resonance 
> frequency
> with an added inductor.
>
> You can get the LTspice file if you like.
>
> regards, Gerhard
>
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Re: [time-nuts] Effect of EFC noise on phase noise

[Alex Pummer]

Ja Gerhard, bitte schicke mir den LTSpice file,

Danke im Voraus und
73
KJ6UHN
Alex

On 8/1/2016 6:34 PM, Gerhard Hoffmann wrote:

Am 02.08.2016 um 02:42 schrieb Bruce Griffiths:

/"I'm working on a new amplifier based on IF3602 or BF862 FETs that can
use 10u foil only."/
/
/
Similar to that published by Groner in Linear Audio?
/
/
I know that Groner exists from some web site, but had no personal 
contact.
Also I don't read Linear Audio other than 2 articles from Scott Wurcer 
that I've bought.
I highly regard Scott, he's the father of the AD797 after all and AD 
fellow.

I also had some conversations with him on that.

The preamp will be classical.  Some JFETs in parallel, no source 
resistors except

half an Ohm for feedback, more would add to the input noise voltage.
Cascode with a Zetex bipolar (or whatever they are called now).
OP37 for loop gain. feedback from OP37 output for 50 or 60 dB gain.
Post amplifier to 80 db or so.
Without the cascode, the 1 MHz is not possible. It does not help that
the feedback limits the voltage excursions on the drain.

I'm not yet sure about the effective input capacitance. I get abt. 1 
or 1.5 MHz

bandwidth from a low impedance source. A few nF on the input capacitance
would be ok, in the end I want it after a ring mixer for phase noise 
measurements
but I get unreasonably more in simulation, depending on if I measure 
it from
upper frequency corner with a larger input resistor or the resonance 
frequency

with an added inductor.

You can get the LTspice file if you like.

regards, Gerhard

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08/01/16


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